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Optimal forage grass germplasm for drought-prone Mediterranean environments
Field Crops Research 148 (2013) 9–14
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Optimal forage grass germplasm for drought-prone Mediterranean environments P. Annicchiarico a,∗ , L. Pecetti a , A. Abdelguerfi b , H. Bouzerzour c , R. Kallida d , C. Porqueddu e , N.M. Simões f , F. Volaire g a Consiglio per la Ricerca e la Sperimentazione in Agricoltura - Centro di Ricerca per le Produzioni Foraggere e Lattiero-Casearie (CRA-FLC), viale Piacenza 29, 26900 Lodi, Italy b Ecole Nationale Supérieure Agronomique (ENSA), El Harrach, 16200 Alger, Algeria c Département de Biologie, Université de Sétif, 1900 Sétif, Algeria d Institut National de la Recherche Agronomique (INRA), Avenue de la Victoire, BP 415 Rabat, Morocco e Istituto per il Sistema Produzione Animale in Ambiente Mediterraneo (CNR-ISPAAM), Traversa La Crucca 3, 07040 Li Punti, Sassari, Italy f Instituto Nacional de Recursos Biològicos (INIA-INRB), Estrada Gil Vas, Apart. 6, 7350 Elvas, Portugal g Centre d’Ecologie Fonctionelle et Evolutive (CEFE), CNRS-INRA-SupAgro, UMR 5175, Route de Mende, 34293 Montpellier, France
a r t i c l e
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Article history: Received 17 February 2012 Accepted 28 March 2013 Keywords: Dactylis glomerata Drought tolerance Festuca arundinacea Genotype × environment interaction Plant adaptation Summer dormancy
a b s t r a c t Extensive livestock production is a basic socio-economic feature of rainfed Mediterranean agriculture that is threatened by overgrazing and desertification of natural grasslands and by climate change. The cultivation of improved, drought-tolerant perennial forages can alleviate these constraints. This study aimed to support breeders in choosing target species and plant types, and agronomists in setting site-specific forage recommendations for the western Mediterranean basin. Three-year dry matter (DM) yield and final survival of two cultivars of cocksfoot (Kasbah, completely summer dormant; Jana, non-dormant) and two of tall fescue (Centurion and Flecha, both incompletely dormant) that were top-performing in previous studies were assessed in six rainfed sites of Algeria, France, Italy, Morocco and Portugal. Site mean annual water for the crop ranged from 321 to 669 mm. On average, tall fescue displayed higher DM yield and a slight trend towards greater persistence than cocksfoot. However, species and cultivars within species displayed interaction with location. Factorial regression was preferable to other techniques for modelling adaptive responses. Cultivar DM yield was modelled as a function of spring–summer (April–September) drought stress and late-spring (May–June) daily maximum temperatures of locations, whereas cultivar final survival was modelled as a function of mean annual water available and absolute minimum temperature of locations. Indications on expected best-performing material were produced for combinations of these climatic variables, highlighting the excellent yielding ability of Flecha across drought-prone environments, the good persistence of Flecha and Kasbah in most environments, and the adaptation of the remaining cultivars to specific climatic conditions. Besides driving cultivar recommendations, our results can support breeders’ decisions also in view of predicted climate changes. Tall fescue has general interest for Mediterranean drought-prone areas. Completely summer-dormant cocksfoot germplasm could also be useful for these areas, especially the warmer ones, if its yielding ability in the cool season could definitely be improved. © 2013 Elsevier B.V. All rights reserved.
1. Introduction Extensive livestock production is a basic socio-economic feature of the Mediterranean basin, where it enhances farmers’ stability against economic shocks and crop failures and favours labour optimization and resource re-utilization on the farm (FAO, 2010). However, its environmental and economic sustainability is jeopardized by overgrazing and desertification of natural grasslands
∗ Corresponding author. Tel.: +39 0371404751; fax: +39 037131853. E-mail address: [email protected] (P. Annicchiarico). 0378-4290/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.fcr.2013.03.024
which are due to increasing livestock numbers and cereal cropping area (Nefzaoui, 2004; FAO, 2010), exacerbated by greater drought predicted from climate change (arising from less rainfall and higher temperatures: IPCC, 2007). While climate change may hasten the trend towards desertification, overgrazing and desertification may in turn contribute to climate change by raising temperatures locally (Nasrallah and Balling, 2004) and sequestering less carbon dioxide (FAO, 2010). Thus, the rainfed cropping of improved drought-tolerant forage crops has crucial importance both for safeguarding the economic and environmental sustainability of crop-livestock systems, and for mitigation of and adaptation to climate change in climatically unfavourable Mediterranean areas.
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Perennial forage species could be a valuable alternative to the predominantly used drought-escaping annual species, as they offer greater optimization of water availability by more rapid regrowth at the onset of the autumn rains and more efficient exploitation of residual moisture in late spring compared with annuals (Porqueddu et al., 2005; Lelièvre and Volaire, 2009). In addition, perennials also reduce the risk of soil erosion and the costs associated with tilling and sowing relative to annual species. Their successful adoption, however, depends on their ability to survive across successive summer droughts. Tall fescue [Lolium arundinaceum (Schreb.) Darbysh, syn. Festuca arundinacea Schreb.] and cocksfoot (Dactylis glomerata L.) can be regarded as the main perennial forage species for semi-arid environments (Reed et al., 1999; Nie et al., 2004, 2008). Both species include Mediterranean and temperate plant types which differ for morphophysiological and adaptive characteristics (Ghesquière and Jadas-Hécart, 1995; Mousset, 1995). Their cultivation in Mediterranean environments is limited by the paucity of adapted cultivars (Lelièvre and Volaire, 2009), as these species have usually been bred in and for more temperate climates. However, adapted material could be found both for tall fescue (Pecetti et al., 2011) and cocksfoot (Annicchiarico et al., 2011) within Mediterranean germplasm evaluated across drought-prone Mediterranean sites. The comparison of elite tall fescue and cocksfoot germplasm under stressful conditions would be valuable for: (i) defining priorities for regional or national breeding programmes, also in view of the limited resources available for public or private breeding of forage species and (ii) defining forage germplasm recommendations for different stress environments. The few reported comparisons are relative to Australian or French environments. Nie et al. (2008) found both tall fescue and cocksfoot among the most persistent temperate perennial species in a five-year evaluation across seven Australian locations. A Mediterranean ecotype of tall fescue outyielded a Mediterranean cultivar of cocksfoot over four years in a semi-arid Australian environment, while showing similar final persistence (Reed, 1996). The two species displayed comparable adaptation to drought stress in southern France, with survival depending more on the origin of the germplasm (i.e., Mediterranean or not) than on the species (Volaire, 2008). Different drought-tolerance strategies were reported by Volaire and Lelièvre (2001) for the two species, with more efficient dehydration tolerance in cocksfoot and better dehydration delay through deeper water uptake in tall fescue. Some cocksfoot germplasm exploits a dominant strategy of water conservation under stress that relies on complete summer dormancy, i.e., the complete arrest of vegetation in summer irrespective of water availability (Volaire, 2008). This strategy has never been observed in tall fescue (Norton et al., 2007).
This study focuses on the best cultivars of tall fescue and cocksfoot that were identified by Pecetti et al. (2011) and Annicchiarico et al. (2011) for each species across a set of locations of the western Mediterranean basin. It aims to contribute to priority setting by breeding programmes and optimal germplasm targeting by agronomists in the region, by comparing species and cultivars within species on the grounds of modelled adaptive responses of cultivars for three-year forage yield and final survival. 2. Materials and methods 2.1. Experimental data The evaluation comprised six test locations, namely, Elvas in south-eastern Portugal, Montpellier in southern France, Sassari in Sardinia (Italy), Alger and Sétif in coastal and inner Algeria, respectively, and Merchouch in inner Morocco. The experiments hosted in these sites provided the experimental data for the earlier, separate studies on the two species, which included seven cocksfoot (Annicchiarico et al., 2011) and five tall fescue cultivars (Pecetti et al., 2011). Their data were exploited for this study with respect to a subset of two cocksfoot and two tall fescue cultivars, since cocksfoot and tall fescue materials were actually grown in the same experiment as randomized entries within each randomized complete block. The geographical co-ordinates of the sites are given in Table 1. All sites had altitude lower than 400 m above sea level except for Sétif, located at 1081 m elevation. Soils were not shallow (>0.90 m), and ranged from sandy loam to clay for texture and from 7.4 to 8.3 for pH (in H2 O). The cultivars included in this study were Kasbah and Jana of cocksfoot, and Flecha and Centurion of tall fescue. Each of these cultivars was top-performing in a subset of sites in the separate studies for each species (Annicchiarico et al., 2011; Pecetti et al., 2011). The region of selection and the geographic origin of each cultivar are reported in Table 2. All cultivars were bred from Mediterranean germplasm. Kasbah belongs to subsp. hispanica of D. glomerata and is completely summer dormant (Volaire, 2008). Jana belongs to subsp. glomerata and is substantially non-dormant (Piano et al., 2004). Flecha and Centurion are both incompletely dormant, i.e., with restricted summer growth upon available water and without endogenous late-spring senescence (Norton et al., 2007). Each experiment was designed as a randomized complete block with four replications, and was run under rainfed conditions for three years. A modest supplemental irrigation was provided only in the sowing year at Montpellier, Alger, Sétif and Merchouch, to favour seedling establishment. In Montpellier, a rainout shelter was placed over the plots from around mid-June to around mid-September (at least for 100 days in each year), to increase
Table 1 Geographic position, total number of cuts, mean values of climatic variables across test years, and mean value of three-year dry matter yield and final row cover of four grass cultivars, for six test locations.
Area Latitude Longitude Total number of cuts Annual water (mm) April–September water (mm) Annual drought stress (mm)a April–September drought stress (mm)a Annual absolute min. temp. (◦ C) May–June daily max. temp. (◦ C) Dry matter yield (t/ha)b Final row cover (%)b a b
Alger
Elvas
Merchouch
Montpellier
Sassari
Sétif
Coastal Algeria 36◦ 45 N 3◦ 3 E 8 669 110 499 696 –0.3 28.8 19.98b 84.1ab
Portugal 38◦ 52 N 7◦ 9 W 13 473 149 536 630 –2.0 27.5 25.59a 54.7c
Morocco 33◦ 33 N 6◦ 41 W 8 321 74 1019 844 0.4 26.7 16.65bc 54.1c
South France 43◦ 36 N 3◦ 53 E 12 506 236 428 486 –6.4 25.2 18.72bc 79.1b
Sardinia 40◦ 46 N 8◦ 28 E 9 540 158 609 676 –0.3 26.7 16.15c 89.5a
Inland Algeria 36◦ 11 N 5◦ 24 E 7 399 196 827 717 –6.7 32.7 6.54d 46.4d
As difference between estimated long-term potential evapotranspiration and actual water available for the crop. Row means with different letter differ at P < 0.05 according to Newman–Keuls test.
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Table 2 Species, name, origin, and mean three-year dry matter yield and final row cover of four grass cultivars grown in six locations. Species
Name
Region of selection
Germplasm area of origin
Dry matter yield (t/ha)
Final row cover (%)
Cocksfoot Cocksfoot Tall fescue Tall fescue
Jana Kasbah Centurion Flecha
Sardinia Australia South France Argentina
Sardinia; Algeria Morocco Morocco; Tunisia Tunisia
14.16c 12.85c 19.29b 22.79a
55.7c 75.3a 65.5b 75.3a
Means with different letter differ at P < 0.05 according to Newman–Keuls test.
the drought stress severity. The experiments were drill-sown at 25 kg/ha seed rate in autumn 2004 in Montpellier, Sassari and Alger and in autumn 2005 in the remaining sites. Each plot had 5 m2 size and included 10 rows 2.5 m long spaced 0.2 m, keeping an harvest area of 2.4 m2 . Pre-sowing fertilization was site-specific depending on results of soil analyses and included at least 20 kg/ha of P2 O5 . Nitrogen fertilization, split into two or three applications per year, was site-specific as a function of local practices and crop productivity and ranged from 130 kg/ha of N in Sétif to 450 kg/ha in Elvas over the crop cycle. Cultivar dry matter (DM) yield net of any weeds was recorded over three cropping years plus the first autumn harvest following the third summer. The total number of harvests ranged from 7 in Sétif to 13 in Elvas depending on the site growth potential. The first harvest occurred when at least half of the overall evaluated cultivars reached the heading stage. The persistence of the genotypes was assessed in terms of final row cover in the autumn regrowth following the third summer, estimating visually the row cover percentage of each row within the harvest area and then computing the average plot value. Daily values of rainfall and temperatures were recorded at each station. Long-term monthly values of potential evapotranspiration according to the Penman–Monteith method (PETPM ) were estimated from temperature data according to De Pauw et al. (2004). Drought stress was computed as the difference between long-term PETPM values and actual water available for the crop (rainfall plus possible supplemental irrigation).
2.2. Statistical analysis The data were subjected to: (i) an analysis of variance (ANOVA), to verify the variation among cultivars in each site and (ii) a combined ANOVA including cultivar and location as fixed factors and block within location as a random factor, to assess genotype (i.e. cultivar) and location main effects and genotype × location (GL) interaction. Cultivar main effects and GL interaction effects were further partitioned into effects due to species and cultivars within species. Cultivar adaptive responses for DM yield and final row cover were modelled by three major techniques, namely: (i) joint regression, where GL interaction effects are modelled by genotype regression as a function of the location mean value (Finlay and Wilkinson, 1963); (ii) additive main effects and multiplicative interaction (AMMI), where modelled GL effects are accounted for by the statistically significant axes of a double-centred principal components analysis performed on the GL interaction matrix (Gauch, 1992); and (iii) factorial regression, where GL effects are modelled by genotype regression as a function of one or more environmental variables (Denis, 1988). Modelled data were preferred to observed data not only because of their clearer display of adaptive responses and greater insight into environmental and genotypic factors underlying these responses (Annicchiarico, 2002), but also because of their greater theoretical (Gauch, 1992) and empirical (Annicchiarico et al., 2006) ability to predict future responses of the cultivars. Modelling and its integration with ANOVA always related to original data, according to Gauch’s (Gauch, 1988) suggestion to give
priority to these data rather than transformed ones when the latter are far less meaningful agronomically. However, we verified that row cover data subjected to angular transformation provided same results as original data with regard to significance of GL interaction effects and cultivar response in the analysis of adaptation (data not reported). Thirteen climatic, soil or sward management variables were considered as possible environmental covariates for factorial regression, namely: (i) the six climatic variables listed in Table 1, as well as the mean number of frost days and the mean summer (July–August) daily maximum temperature, which related to the level of drought, cold or heat stress of the sites; (ii) content of clay, sand and P2 O5 (Olsen method), and pH, of the soil; and (iii) total number of harvests. Factorial regression was carried out according to Denis (1988), identifying the best one-covariate model and then searching for additional covariates according to a stepwise forward selection strategy. GL interaction principal component (PC) axes for AMMI modelling were tested by the FR test, in view of its greater robustness to non-normality and heteroscedasticity of errors compared with other tests (Piepho, 1995). An AMMI, joint regression or factorial regression model was considered adequate if: (i) genotype variation for its parameters was significant at P < 0.01 (as more liberal P levels implied, for experiments not repeated in time, a greater danger to model GL effects with limited repeatability in time) and (ii) its residual GL interaction, tested on the pooled experimental error, was below P < 0.01 significance. Adequate models were compared for predictive ability by the criterion described by Annicchiarico (2009) based on the sum of the estimated variances of relevant GL interaction components (the entry regressions component, for joint regression; one component for each significant PC axis, for AMMI; one component for each significant covariate, for factorial regression), using formulae reported in that paper. An empirical assessment (Annicchiarico, 2009) indicated the better ability of this criterion to predict site-specific top-yielding entries relative to the criterion proposed by Brancourt-Hulmel et al. (1997). The best factorial regression models identified for DM yield and final row cover were exploited for targeting cultivars by computing the expected cultivar values as a function of different values of the relevant covariates and comparing these values by Dunnett’s one-tailed test (Annicchiarico et al., 2006). This test held the average experiment error as error term, and adopted P < 0.10 as Type 1 error rate to achieve a better balance with Type 2 error rates (Annicchiarico et al., 2006). The software CropStat (formerly IrriStat) released by the International Rice Research Institute (IRRI, 2009) was used for joint regression and AMMI modelling as well as for factorial regression, for which no specific module is available but other routines can be exploited as described in Annicchiarico (2002). The Statistical Analysis System (SAS) software was used for the remaining analyses.
3. Results and discussion Site annual water available for the crop, which varied from 321 to 669 mm (Table 1), had wider range and was inclusive of lower values than earlier field-based comparisons of cocksfoot and tall fescue species reported by Nie et al. (2008; range of annual rainfall about 400 mm to 620 mm) and Reed (1996; 550 mm annual
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rainfall). Montpellier exhibited the lowest level of drought stress (despite the rain shelter) and Merchouch the highest, according to site mean values of drought stress over the year or over spring and summer (April–September) (Table 1). Cold winters were a feature of Sétif (mean number of frost days per year = 68; average annual absolute minimum temperature = −6.7 ◦ C) and, to a lesser extent, Montpellier (30 frost days on average; annual absolute minimum temperature = −6.4 ◦ C). Locations differed for mean DM yield and final row cover in the combined ANOVA (Table 3). Sétif, subjected to severe drought and cold stress and high late-spring temperatures, displayed lower mean values of these traits relative to other sites (Table 1). Severe plant mortality also featured Merchouch and Elvas (Table 1). In the latter site, climatically rather favourable and characterized by high forage yield, a sharp reduction in plant density occurred only in the last cropping year (data not reported). The ANOVA detected significant (P < 0.01) genotype and GL interaction variation for total DM yield and final row cover which were due to species and cultivars within species effects (Table 3). For both genotype and GL interaction, the size of mean squares suggested the greater importance of species variation for DM yield and of cultivars within species variation for final row cover (Table 3). Mean values of the genotypes indicated the forage yield advantage of the two tall fescue cultivars over the two cocksfoot cultivars (Table 2). Flecha outyielded any other cultivar while showing the same, top-ranking persistence as the completely summer-dormant cocksfoot Kasbah (Table 2). The non-dormant cocksfoot Jana displayed the lowest mean persistence (Table 2). On the whole, the mean performance of species agreed with results by Nie et al. (2008) and Reed (1996) for Australian environments indicating the higher DM yield and the slight trend towards greater persistence of tall fescue relative to cocksfoot. The joint regression model did not fit adequately GL interaction effects for DM yield or final row cover, as indicated by the lack of variation among genotype regressions (Table 3). The AMMI model including one GL interaction PC axis (AMMI-1) was adequate for both variables. Another adequate model for DM yield was factorial regression of genotype responses as a function of spring–summer (April–September) drought stress and late-spring (May–June) daily maximum temperatures of locations. This model,
compared with AMMI-1, was slightly less accurate (about 71% vs. 76% of GL interaction variation accounted for) but more parsimonious (6 vs. 7 GL interaction degrees of freedom) and, on the whole, more predictive according to the criterion based on the sum of the estimated variances of relevant GL interaction components (sum of two variance components for the two-covariate factorial regression model = 6.22; variance component for AMMI-1 = 2.82). The twocovariate factorial regression model including mean annual water available and absolute minimum temperature of locations was adequate for final row cover, for which it tended towards somewhat greater predictive ability than AMMI-1 when comparing the estimated variances of relevant GL interaction components for these models (2.05 vs. 1.75). Factorial regression models offered the further advantage relative to AMMI-1 of a straightforward extension of results to non-test locations as a function of site values of the relevant environmental variables. Flecha displayed positive GL interaction for DM yield in locations with greater spring–summer (April–September) drought stress (regression slope > 0), whereas Jana had relatively better yield response in less stressing sites (regression slope < 0; Table 4). In substantial agreement with this result, GL interaction for final row cover was positive in sites with less annual rainfall for Flecha and in wetter sites for Jana (Table 4). Also Kasbah exhibited relatively better persistence in drier locations (Table 4). With respect to temperature patterns, Flecha showed positive GL interaction for DM yield in cooler sites in late spring, and Jana relatively better persistence in sites with lower absolute minimum temperature (Table 4). Kasbah was better adapted to warmer sites, as indicated by relatively better yield under higher late-spring temperatures and better persistence under milder winters (Table 4). The expected best-yielding cultivars based on factorial regression modelling as a function of covariate values in the range of test site values are reported in Fig. 1. The tall fescue cultivar Flecha tended to outyield any other cultivar in environments with high drought stress or fairly cool late spring. The south-European cultivars Centurion of tall fescue and Jana of cocksfoot emerged among the top-yielding genotypes under moderate drought stress and high late-spring temperatures. Kasbah was among the topyielding genotypes only under highest late-spring temperatures (32 ◦ C) combined with intermediate drought stress (Fig. 1).
Table 3 Analysis of variance for three-year dry matter yield and final row cover of two cocksfoot and two tall fescue cultivars grown in six locations. Cultivar × location interaction partitioned by (a) species and cultivar within species factors, (b) joint regression, (c) additive main effects and multiplicative interaction, and (d) factorial regression modelling. Source of variation
Degrees of freedom
Cultivar (a) Species Cultivar (Species) Location Cultivar × Location (a) Species × Location Cultivar (Species) × Location (b) Heterogeneity of regressions Deviations from regression (c) PC 1 Residual (d) April–September drought stressb May–June max. daily temperatures Residual Annual water available Annual absolute min. temperature Residual Pooled error
3 1 2 5 15 5 10 3 12 7 8 3 3 9 3 3 9 54
a b * **
Mean squarea Dry matter yield
Final row cover
510.76** 1364.48** 83.90** 625.30** 46.97** 89.82** 25.55** 63.44 NS 42.86** 76.10** 21.49* 86.97** 79.15** 22.91* – – – 8.41
2118.8** 574.1** 2891.2** 5372.2** 738.0** 566.6** 823.6** 1007.2 NS 710.3** 1290.6** 254.3 NS – – – 1809.5** 1214.3** 222.0 NS 139.6
NS, not significant. As difference between estimated long-term potential evapotranspiration and actual water available for the crop. Significant at P < 0.05. Significant at P < 0.01.
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Table 4 Parameters for factorial regression modelling of cultivar × location interaction for three-year dry matter yield as a function of April–September drought stress (DS) and May–June daily maximum temperatures (MaxT) and for final row cover as a function of annual water available for the crop (AW) and annual absolute minimum temperature (MinT), for four grass cultivars grown in six locations. Cultivar
Jana Kasbah Centurion Flecha a * **
Dry matter yield (t/ha)
Final row cover (%)
Intercept
 DSa
−1.13 −23.08 9.81 14.40
−0.0233 −0.0001 −0.0028 0.0270** *
 MaxT
Intercept
0.604 0.849* −0.284 −1.168**
−70.69 35.88 8.97 25.83
 AW
 MinT **
0.1310 −0.0578* −0.0225 −0.0506*
−2.830** 3.080** −0.755 0.505
As difference between estimated long-term potential evapotranspiration and actual water available for the crop. Different from zero at P < 0.05. Different from zero at P < 0.01.
The picture was partly different when considering the persistence as predicted by factorial regression-modelled final row cover (Fig. 1). Kasbah and Flecha were top-ranking in most environments, especially where winter was milder. Jana and Centurion were among the best-persisting genotypes when winter was colder, with outstanding persistence displayed by Jana in environments also featuring fairly high annual rainfall. The widespread yield advantage of tall fescue over cocksfoot may largely derive from greater growth across autumn and winter (Lelièvre et al., 2011). The cocksfoot Kasbah maximized the drought tolerance and persistence through its complete dormancy trait, but its intrinsically low yield potential that is typical of the cocksfoot subsp. hispanica (Piano et al., 2004) led to lower predicted forage yield than the best-performing tall fescue (Flecha) even under extreme drought stress conditions. The high level of persistence attained by Flecha arose from survival mechanisms other than complete dormancy, such as the deep root system (Lelièvre et al., 2011) and the development of an extensive collar of senescent leaf
sheaths around its young tillers in summer (which could increase tiller survival by reducing transpiration losses: Norton et al., 2006). The fairly deep soil which featured the current environments did not limit the expression of the tall fescue deep root trait and its usefulness as a drought avoidance mechanism. The cocksfoot cultivar Jana outyielded Kasbah under low to medium drought stress, while being less persistent in all conditions but the high-rainfall, cold-prone ones. This adaptive response can be accounted for by the higher plant vigour of subsp. glomerata relative to subsp. hispanica, the lack of summer dormancy, and the selection for responsiveness to supplemental irrigation in a relatively temperate region of Jana (Piano et al., 2004). This cultivar has repeatedly shown wide adaptation across favourable to moderately drought stress conditions compared with other cultivars of subsp. glomerata (Piano et al., 2004; Annicchiarico et al., 2011), suggesting a possible dehydration tolerance trait that would be insufficient and less useful than complete summer dormancy for survival under severe summer drought. The indications on top-performing material in Fig. 1 can be exploited for the site-specific targeting of grass cultivars as a function of the expected values of the relevant climatic variables on the site. A previous study on durum wheat indicated the substantial reliability of factorial regression-based recommendations (Annicchiarico et al., 2006). Forage quality would also be an issue for cultivar recommendations, but the only difference that emerged from the analysis of quality traits across three harvests in Elvas and in Sassari was the higher protein content of cocksfoot over tall fescue (about 15% vs. 13.6%: Porqueddu and Simões, unpublished results). 4. Conclusion
Fig. 1. Best cultivars for three-year dry matter yield and final row cover for different levels of relevant climatic variables in a two-covariate factorial regression model (cultivars are reported in descending rank order, excluding those which are inferior to the top-ranking one at P < 0.10; see Table 4 for factorial regression parameters).
The environmental covariates retained for factorial regressions indicated drought stress (either as spring–summer water deficit or as annual water available for the crop) as the main environmental determinant of cultivar adaptive responses across sites of the western Mediterranean basin, but revealed that also responses to temperature patterns had some bearing on genotype adaptation. The contrasting responses to rainfall and low temperatures of the two cocksfoot cultivars for final row cover, and the differences between cultivars in each species for other regression parameters, highlighted the wide variation for specific-adaptation pattern that may characterize elite cultivars within species and its relevance for species comparison. The generated information can drive the recommendation of grass species and cultivars as a function of known long-term local climatic data. Besides, it can help regional breeding programmes with limited resources available in choosing target species and plant types, taking also account of the predicted increase of drought and late-spring temperatures due to climate change. The expected yield and persistence responses in Fig. 1 suggest that Mediterranean tall fescue has general interest for drought-prone areas. A
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completely summer dormant cocksfoot could also be useful for the same areas, especially the warmer ones, if its persistence could be combined with definitely higher forage yielding ability in the cool season. Acknowledgements This study was funded by the EU FP6 project PERMED (INCO2004-509140). We dedicate this study to the memory of Dr. F. Lelièvre, who co-ordinated the project. We thank Dr. E. De Pauw for estimating site evapotranspiration, and P. Chapon, I. Duarte, A. Khedim, M. Mefti, P. Saba and A. Souihka for excellent technical assistance. References Annicchiarico, P., 2002. Genotype x Environment Interactions: Challenges and Opportunities for Plant Breeding and Cultivar Recommendations. FAO Plant Production and Protection Paper No. 174. FAO, Rome, 115 pp. Annicchiarico, P., 2009. Coping with and exploiting genotype x environment interactions. In: Ceccarelli, S., Guimarães, E.P., Weltzien, E. (Eds.), Plant Breeding and Farmer Participation. FAO, Rome, pp. 519–564. Annicchiarico, P., Bellah, F., Chiari, T., 2006. Repeatable genotype x location interaction and its exploitation by conventional and GIS-based cultivar recommendation for durum wheat in Algeria. Eur. J. Agron. 24, 70–81. Annicchiarico, P., Pecetti, L., Bouzerzour, H., Kallida, R., Khedim, A., Porqueddu, C., Simões, N.M., Volaire, F., Lelièvre, F., 2011. Adaptation of contrasting cocksfoot plant types to agricultural environments across the Mediterranean basin. Environ. Exp. Bot. 74, 82–89. Brancourt-Hulmel, M., Biarnès-Dumoulin, V., Denis, J.B., 1997. Points de repère dans l‘analyse de la stabilité et de l‘interaction génotype-milieu en amélioration des plants. Agronomie 17, 219–246. Denis, J.B., 1988. Two-way analysis using covariates. Statistics 19, 123–132. De Pauw, E., Ghaffari, A., Ghasemi, V., 2004. Agroclimatic zones map of Iran: explanatory notes. Research Report, Natural Resources Management Program. ICARDA, Aleppo, Syria, 44 pp. FAO, 2010. The State of Food and Agriculture. Livestock in the Balance. FAO, Rome, 176 pp. Finlay, K.W., Wilkinson, G.N., 1963. The analysis of adaptation in a plant-breeding programme. Aust. J. Agric. Res. 14, 742–754. Gauch, H.G., 1988. Model selection and validation for yield trials with interaction. Biometrics 44, 705–715. Gauch, H.G., 1992. Statistical Analysis of Regional Yield Trials: AMMI Analysis of Factorial Designs. Elsevier, Amsterdam, 278 pp. Ghesquière, M., Jadas-Hécart, J., 1995. Les fétuques ou le genre Festuca. In: Prosperi, J.-M., Guy, P., Balfourier, F. (Eds.), Ressources Génétiques des Plantes Fourragères et à Gazon. INRA-BRG, Paris, pp. 53–70. IPCC, 2007. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, 2007. Cambridge University Press, Cambridge, UK, 938 pp.
IRRI, 2009. CropStat Version 7.2. IRRI, Manila, 379 pp. Lelièvre, F., Volaire, F., 2009. Current and potential development of perennial grasses in rainfed Mediterranean farming systems. Crop Sci. 49, 2371–2378. Lelièvre, F., Seddaiu, G., Ledda, L., Porqueddu, C., Volaire, F., 2011. Water use efficiency and drought survival in Mediterranean perennial forage grasses. Field Crops Res. 121, 333–342. Mousset, C., 1995. Les dactyls ou le genre Dactylis. In: Prosperi, J.-M., Guy, P., Balfourier, F. (Eds.), Ressources Génétiques des Plantes Fourragères et à Gazon. INRA-BRG, Paris, pp. 28–52. Nasrallah, H.A., Balling, R.C., 2004. Impact of desertification on temperature trends in the Middle East. Environ. Monit. Assess. 37, 265–271. Nefzaoui, A., 2004. Rangeland improvement and management options in the arid environment of Central and South Tunisia. Options Méditerranéennes, Series A, 59, 15–25. Nie, Z.N., Chapman, D.F., Tharmaraj, J., Clements, R., 2004. Effects of pasture species mixture, management, and environment on the productivity and persistence of dairy pastures in south-west Victoria. 1. Herbage accumulation and seasonal growth pattern. Aust. J. Agric. Res. 55, 625–636. Nie, Z.N., Miller, S., Moore, G.A., Hackney, B.F., Boschma, S.P., Reed, K.F.M., Mitchell, M., Albertsen, T.O., Clark, S., Craig, A.D., Kearney, G., Li, G.D., Dear, B.S., 2008. Field evaluation of perennial grasses and herbs in southern Australia. 2. Persistence, root characteristics and summer activity. Aust. J. Exp. Agric. 48, 424–435. Norton, M.R., Lelièvre, F., Volaire, F., 2006. Summer dormancy in Dactylis glomerata L.: the influence of seasonal sowing and a simulated mid-summer storm on two contrasting cultivars. Aust. J. Agric. Res. 57, 565–575. Norton, M.R., Volaire, F., Lelièvre, F., 2007. Measuring summer dormancy in temperate perennial grasses. In: Rosellini, D., Veronesi, F. (Eds.), Breeding and Seed Production for Conventional and Organic Agriculture. University of Perugia, Perugia, Italy, pp. 353–356. Pecetti, L., Annicchiarico, P., Abdelguerfi, A., Kallida, R., Mefti, M., Porqueddu, C., Simões, N.M., Volaire, F., Lelièvre, F., 2011. Response of Mediterranean tall fescue cultivars to contrasting agricultural environments and implications for selection. J. Agric. Crop Sci. 197, 12–20. Piano, E., Pecetti, L., Annicchiarico, P., Carroni, A.M., Fornasier, F., Romani, M., 2004. Combining drought tolerance and responsiveness to summer moisture availability in cocksfoot (Dactylis glomerata L.) germplasm grown in Mediterranean environments. Aust. J. Agric. Res. 55, 1197–1204. Piepho, H.-P., 1995. Robustness of statistical tests for multiplicative terms in the additive main effects and multiplicative interaction model for cultivar trials. Theor. Appl. Genet. 90, 438–443. Porqueddu, C., Maltoni, S., McIvor, J.G., 2005. Strategies to mitigate seasonality of production in grassland-based systems. In: McGilloway, D.A. (Ed.), Grassland: A Global Resource. Wageningen Academic Publ., Wageningen, The Netherlands, pp. 111–122. Reed, K.F.M., 1996. Improving the adaptation of perennial ryegrass, tall fescue, phalaris and cocksfoot for Australia. New Zeal. J. Agric. Res. 39, 457–464. Reed, K.F.M., Cunningham, P.J., Byron, A., Anderson, M.W., 1999. Perennial grasses of Mediterranean origin offer advantages for central western Victorian sheep pasture. Aust. J. Exp. Agric. 39, 275–284. Volaire, F., 2008. Plant traits and functional types to characterise drought survival of pluri-specific perennial herbaceous swards in Mediterranean areas. Eur. J. Agron. 29, 116–124. Volaire, F., Lelièvre, F., 2001. Drought survival in Dactylis glomerata and Festuca arundinacea under similar rooting conditions in tubes. Plant Soil 229, 225–234.
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Optimal forage grass germplasm for drought-prone Mediterranean environments P. Annicchiarico a,∗ , L. Pecetti a , A. Abdelguerfi b , H. Bouzerzour c , R. Kallida d , C. Porqueddu e , N.M. Simões f , F. Volaire g a Consiglio per la Ricerca e la Sperimentazione in Agricoltura - Centro di Ricerca per le Produzioni Foraggere e Lattiero-Casearie (CRA-FLC), viale Piacenza 29, 26900 Lodi, Italy b Ecole Nationale Supérieure Agronomique (ENSA), El Harrach, 16200 Alger, Algeria c Département de Biologie, Université de Sétif, 1900 Sétif, Algeria d Institut National de la Recherche Agronomique (INRA), Avenue de la Victoire, BP 415 Rabat, Morocco e Istituto per il Sistema Produzione Animale in Ambiente Mediterraneo (CNR-ISPAAM), Traversa La Crucca 3, 07040 Li Punti, Sassari, Italy f Instituto Nacional de Recursos Biològicos (INIA-INRB), Estrada Gil Vas, Apart. 6, 7350 Elvas, Portugal g Centre d’Ecologie Fonctionelle et Evolutive (CEFE), CNRS-INRA-SupAgro, UMR 5175, Route de Mende, 34293 Montpellier, France
a r t i c l e
i n f o
Article history: Received 17 February 2012 Accepted 28 March 2013 Keywords: Dactylis glomerata Drought tolerance Festuca arundinacea Genotype × environment interaction Plant adaptation Summer dormancy
a b s t r a c t Extensive livestock production is a basic socio-economic feature of rainfed Mediterranean agriculture that is threatened by overgrazing and desertification of natural grasslands and by climate change. The cultivation of improved, drought-tolerant perennial forages can alleviate these constraints. This study aimed to support breeders in choosing target species and plant types, and agronomists in setting site-specific forage recommendations for the western Mediterranean basin. Three-year dry matter (DM) yield and final survival of two cultivars of cocksfoot (Kasbah, completely summer dormant; Jana, non-dormant) and two of tall fescue (Centurion and Flecha, both incompletely dormant) that were top-performing in previous studies were assessed in six rainfed sites of Algeria, France, Italy, Morocco and Portugal. Site mean annual water for the crop ranged from 321 to 669 mm. On average, tall fescue displayed higher DM yield and a slight trend towards greater persistence than cocksfoot. However, species and cultivars within species displayed interaction with location. Factorial regression was preferable to other techniques for modelling adaptive responses. Cultivar DM yield was modelled as a function of spring–summer (April–September) drought stress and late-spring (May–June) daily maximum temperatures of locations, whereas cultivar final survival was modelled as a function of mean annual water available and absolute minimum temperature of locations. Indications on expected best-performing material were produced for combinations of these climatic variables, highlighting the excellent yielding ability of Flecha across drought-prone environments, the good persistence of Flecha and Kasbah in most environments, and the adaptation of the remaining cultivars to specific climatic conditions. Besides driving cultivar recommendations, our results can support breeders’ decisions also in view of predicted climate changes. Tall fescue has general interest for Mediterranean drought-prone areas. Completely summer-dormant cocksfoot germplasm could also be useful for these areas, especially the warmer ones, if its yielding ability in the cool season could definitely be improved. © 2013 Elsevier B.V. All rights reserved.
1. Introduction Extensive livestock production is a basic socio-economic feature of the Mediterranean basin, where it enhances farmers’ stability against economic shocks and crop failures and favours labour optimization and resource re-utilization on the farm (FAO, 2010). However, its environmental and economic sustainability is jeopardized by overgrazing and desertification of natural grasslands
∗ Corresponding author. Tel.: +39 0371404751; fax: +39 037131853. E-mail address: [email protected] (P. Annicchiarico). 0378-4290/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.fcr.2013.03.024
which are due to increasing livestock numbers and cereal cropping area (Nefzaoui, 2004; FAO, 2010), exacerbated by greater drought predicted from climate change (arising from less rainfall and higher temperatures: IPCC, 2007). While climate change may hasten the trend towards desertification, overgrazing and desertification may in turn contribute to climate change by raising temperatures locally (Nasrallah and Balling, 2004) and sequestering less carbon dioxide (FAO, 2010). Thus, the rainfed cropping of improved drought-tolerant forage crops has crucial importance both for safeguarding the economic and environmental sustainability of crop-livestock systems, and for mitigation of and adaptation to climate change in climatically unfavourable Mediterranean areas.
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Perennial forage species could be a valuable alternative to the predominantly used drought-escaping annual species, as they offer greater optimization of water availability by more rapid regrowth at the onset of the autumn rains and more efficient exploitation of residual moisture in late spring compared with annuals (Porqueddu et al., 2005; Lelièvre and Volaire, 2009). In addition, perennials also reduce the risk of soil erosion and the costs associated with tilling and sowing relative to annual species. Their successful adoption, however, depends on their ability to survive across successive summer droughts. Tall fescue [Lolium arundinaceum (Schreb.) Darbysh, syn. Festuca arundinacea Schreb.] and cocksfoot (Dactylis glomerata L.) can be regarded as the main perennial forage species for semi-arid environments (Reed et al., 1999; Nie et al., 2004, 2008). Both species include Mediterranean and temperate plant types which differ for morphophysiological and adaptive characteristics (Ghesquière and Jadas-Hécart, 1995; Mousset, 1995). Their cultivation in Mediterranean environments is limited by the paucity of adapted cultivars (Lelièvre and Volaire, 2009), as these species have usually been bred in and for more temperate climates. However, adapted material could be found both for tall fescue (Pecetti et al., 2011) and cocksfoot (Annicchiarico et al., 2011) within Mediterranean germplasm evaluated across drought-prone Mediterranean sites. The comparison of elite tall fescue and cocksfoot germplasm under stressful conditions would be valuable for: (i) defining priorities for regional or national breeding programmes, also in view of the limited resources available for public or private breeding of forage species and (ii) defining forage germplasm recommendations for different stress environments. The few reported comparisons are relative to Australian or French environments. Nie et al. (2008) found both tall fescue and cocksfoot among the most persistent temperate perennial species in a five-year evaluation across seven Australian locations. A Mediterranean ecotype of tall fescue outyielded a Mediterranean cultivar of cocksfoot over four years in a semi-arid Australian environment, while showing similar final persistence (Reed, 1996). The two species displayed comparable adaptation to drought stress in southern France, with survival depending more on the origin of the germplasm (i.e., Mediterranean or not) than on the species (Volaire, 2008). Different drought-tolerance strategies were reported by Volaire and Lelièvre (2001) for the two species, with more efficient dehydration tolerance in cocksfoot and better dehydration delay through deeper water uptake in tall fescue. Some cocksfoot germplasm exploits a dominant strategy of water conservation under stress that relies on complete summer dormancy, i.e., the complete arrest of vegetation in summer irrespective of water availability (Volaire, 2008). This strategy has never been observed in tall fescue (Norton et al., 2007).
This study focuses on the best cultivars of tall fescue and cocksfoot that were identified by Pecetti et al. (2011) and Annicchiarico et al. (2011) for each species across a set of locations of the western Mediterranean basin. It aims to contribute to priority setting by breeding programmes and optimal germplasm targeting by agronomists in the region, by comparing species and cultivars within species on the grounds of modelled adaptive responses of cultivars for three-year forage yield and final survival. 2. Materials and methods 2.1. Experimental data The evaluation comprised six test locations, namely, Elvas in south-eastern Portugal, Montpellier in southern France, Sassari in Sardinia (Italy), Alger and Sétif in coastal and inner Algeria, respectively, and Merchouch in inner Morocco. The experiments hosted in these sites provided the experimental data for the earlier, separate studies on the two species, which included seven cocksfoot (Annicchiarico et al., 2011) and five tall fescue cultivars (Pecetti et al., 2011). Their data were exploited for this study with respect to a subset of two cocksfoot and two tall fescue cultivars, since cocksfoot and tall fescue materials were actually grown in the same experiment as randomized entries within each randomized complete block. The geographical co-ordinates of the sites are given in Table 1. All sites had altitude lower than 400 m above sea level except for Sétif, located at 1081 m elevation. Soils were not shallow (>0.90 m), and ranged from sandy loam to clay for texture and from 7.4 to 8.3 for pH (in H2 O). The cultivars included in this study were Kasbah and Jana of cocksfoot, and Flecha and Centurion of tall fescue. Each of these cultivars was top-performing in a subset of sites in the separate studies for each species (Annicchiarico et al., 2011; Pecetti et al., 2011). The region of selection and the geographic origin of each cultivar are reported in Table 2. All cultivars were bred from Mediterranean germplasm. Kasbah belongs to subsp. hispanica of D. glomerata and is completely summer dormant (Volaire, 2008). Jana belongs to subsp. glomerata and is substantially non-dormant (Piano et al., 2004). Flecha and Centurion are both incompletely dormant, i.e., with restricted summer growth upon available water and without endogenous late-spring senescence (Norton et al., 2007). Each experiment was designed as a randomized complete block with four replications, and was run under rainfed conditions for three years. A modest supplemental irrigation was provided only in the sowing year at Montpellier, Alger, Sétif and Merchouch, to favour seedling establishment. In Montpellier, a rainout shelter was placed over the plots from around mid-June to around mid-September (at least for 100 days in each year), to increase
Table 1 Geographic position, total number of cuts, mean values of climatic variables across test years, and mean value of three-year dry matter yield and final row cover of four grass cultivars, for six test locations.
Area Latitude Longitude Total number of cuts Annual water (mm) April–September water (mm) Annual drought stress (mm)a April–September drought stress (mm)a Annual absolute min. temp. (◦ C) May–June daily max. temp. (◦ C) Dry matter yield (t/ha)b Final row cover (%)b a b
Alger
Elvas
Merchouch
Montpellier
Sassari
Sétif
Coastal Algeria 36◦ 45 N 3◦ 3 E 8 669 110 499 696 –0.3 28.8 19.98b 84.1ab
Portugal 38◦ 52 N 7◦ 9 W 13 473 149 536 630 –2.0 27.5 25.59a 54.7c
Morocco 33◦ 33 N 6◦ 41 W 8 321 74 1019 844 0.4 26.7 16.65bc 54.1c
South France 43◦ 36 N 3◦ 53 E 12 506 236 428 486 –6.4 25.2 18.72bc 79.1b
Sardinia 40◦ 46 N 8◦ 28 E 9 540 158 609 676 –0.3 26.7 16.15c 89.5a
Inland Algeria 36◦ 11 N 5◦ 24 E 7 399 196 827 717 –6.7 32.7 6.54d 46.4d
As difference between estimated long-term potential evapotranspiration and actual water available for the crop. Row means with different letter differ at P < 0.05 according to Newman–Keuls test.
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Table 2 Species, name, origin, and mean three-year dry matter yield and final row cover of four grass cultivars grown in six locations. Species
Name
Region of selection
Germplasm area of origin
Dry matter yield (t/ha)
Final row cover (%)
Cocksfoot Cocksfoot Tall fescue Tall fescue
Jana Kasbah Centurion Flecha
Sardinia Australia South France Argentina
Sardinia; Algeria Morocco Morocco; Tunisia Tunisia
14.16c 12.85c 19.29b 22.79a
55.7c 75.3a 65.5b 75.3a
Means with different letter differ at P < 0.05 according to Newman–Keuls test.
the drought stress severity. The experiments were drill-sown at 25 kg/ha seed rate in autumn 2004 in Montpellier, Sassari and Alger and in autumn 2005 in the remaining sites. Each plot had 5 m2 size and included 10 rows 2.5 m long spaced 0.2 m, keeping an harvest area of 2.4 m2 . Pre-sowing fertilization was site-specific depending on results of soil analyses and included at least 20 kg/ha of P2 O5 . Nitrogen fertilization, split into two or three applications per year, was site-specific as a function of local practices and crop productivity and ranged from 130 kg/ha of N in Sétif to 450 kg/ha in Elvas over the crop cycle. Cultivar dry matter (DM) yield net of any weeds was recorded over three cropping years plus the first autumn harvest following the third summer. The total number of harvests ranged from 7 in Sétif to 13 in Elvas depending on the site growth potential. The first harvest occurred when at least half of the overall evaluated cultivars reached the heading stage. The persistence of the genotypes was assessed in terms of final row cover in the autumn regrowth following the third summer, estimating visually the row cover percentage of each row within the harvest area and then computing the average plot value. Daily values of rainfall and temperatures were recorded at each station. Long-term monthly values of potential evapotranspiration according to the Penman–Monteith method (PETPM ) were estimated from temperature data according to De Pauw et al. (2004). Drought stress was computed as the difference between long-term PETPM values and actual water available for the crop (rainfall plus possible supplemental irrigation).
2.2. Statistical analysis The data were subjected to: (i) an analysis of variance (ANOVA), to verify the variation among cultivars in each site and (ii) a combined ANOVA including cultivar and location as fixed factors and block within location as a random factor, to assess genotype (i.e. cultivar) and location main effects and genotype × location (GL) interaction. Cultivar main effects and GL interaction effects were further partitioned into effects due to species and cultivars within species. Cultivar adaptive responses for DM yield and final row cover were modelled by three major techniques, namely: (i) joint regression, where GL interaction effects are modelled by genotype regression as a function of the location mean value (Finlay and Wilkinson, 1963); (ii) additive main effects and multiplicative interaction (AMMI), where modelled GL effects are accounted for by the statistically significant axes of a double-centred principal components analysis performed on the GL interaction matrix (Gauch, 1992); and (iii) factorial regression, where GL effects are modelled by genotype regression as a function of one or more environmental variables (Denis, 1988). Modelled data were preferred to observed data not only because of their clearer display of adaptive responses and greater insight into environmental and genotypic factors underlying these responses (Annicchiarico, 2002), but also because of their greater theoretical (Gauch, 1992) and empirical (Annicchiarico et al., 2006) ability to predict future responses of the cultivars. Modelling and its integration with ANOVA always related to original data, according to Gauch’s (Gauch, 1988) suggestion to give
priority to these data rather than transformed ones when the latter are far less meaningful agronomically. However, we verified that row cover data subjected to angular transformation provided same results as original data with regard to significance of GL interaction effects and cultivar response in the analysis of adaptation (data not reported). Thirteen climatic, soil or sward management variables were considered as possible environmental covariates for factorial regression, namely: (i) the six climatic variables listed in Table 1, as well as the mean number of frost days and the mean summer (July–August) daily maximum temperature, which related to the level of drought, cold or heat stress of the sites; (ii) content of clay, sand and P2 O5 (Olsen method), and pH, of the soil; and (iii) total number of harvests. Factorial regression was carried out according to Denis (1988), identifying the best one-covariate model and then searching for additional covariates according to a stepwise forward selection strategy. GL interaction principal component (PC) axes for AMMI modelling were tested by the FR test, in view of its greater robustness to non-normality and heteroscedasticity of errors compared with other tests (Piepho, 1995). An AMMI, joint regression or factorial regression model was considered adequate if: (i) genotype variation for its parameters was significant at P < 0.01 (as more liberal P levels implied, for experiments not repeated in time, a greater danger to model GL effects with limited repeatability in time) and (ii) its residual GL interaction, tested on the pooled experimental error, was below P < 0.01 significance. Adequate models were compared for predictive ability by the criterion described by Annicchiarico (2009) based on the sum of the estimated variances of relevant GL interaction components (the entry regressions component, for joint regression; one component for each significant PC axis, for AMMI; one component for each significant covariate, for factorial regression), using formulae reported in that paper. An empirical assessment (Annicchiarico, 2009) indicated the better ability of this criterion to predict site-specific top-yielding entries relative to the criterion proposed by Brancourt-Hulmel et al. (1997). The best factorial regression models identified for DM yield and final row cover were exploited for targeting cultivars by computing the expected cultivar values as a function of different values of the relevant covariates and comparing these values by Dunnett’s one-tailed test (Annicchiarico et al., 2006). This test held the average experiment error as error term, and adopted P < 0.10 as Type 1 error rate to achieve a better balance with Type 2 error rates (Annicchiarico et al., 2006). The software CropStat (formerly IrriStat) released by the International Rice Research Institute (IRRI, 2009) was used for joint regression and AMMI modelling as well as for factorial regression, for which no specific module is available but other routines can be exploited as described in Annicchiarico (2002). The Statistical Analysis System (SAS) software was used for the remaining analyses.
3. Results and discussion Site annual water available for the crop, which varied from 321 to 669 mm (Table 1), had wider range and was inclusive of lower values than earlier field-based comparisons of cocksfoot and tall fescue species reported by Nie et al. (2008; range of annual rainfall about 400 mm to 620 mm) and Reed (1996; 550 mm annual
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rainfall). Montpellier exhibited the lowest level of drought stress (despite the rain shelter) and Merchouch the highest, according to site mean values of drought stress over the year or over spring and summer (April–September) (Table 1). Cold winters were a feature of Sétif (mean number of frost days per year = 68; average annual absolute minimum temperature = −6.7 ◦ C) and, to a lesser extent, Montpellier (30 frost days on average; annual absolute minimum temperature = −6.4 ◦ C). Locations differed for mean DM yield and final row cover in the combined ANOVA (Table 3). Sétif, subjected to severe drought and cold stress and high late-spring temperatures, displayed lower mean values of these traits relative to other sites (Table 1). Severe plant mortality also featured Merchouch and Elvas (Table 1). In the latter site, climatically rather favourable and characterized by high forage yield, a sharp reduction in plant density occurred only in the last cropping year (data not reported). The ANOVA detected significant (P < 0.01) genotype and GL interaction variation for total DM yield and final row cover which were due to species and cultivars within species effects (Table 3). For both genotype and GL interaction, the size of mean squares suggested the greater importance of species variation for DM yield and of cultivars within species variation for final row cover (Table 3). Mean values of the genotypes indicated the forage yield advantage of the two tall fescue cultivars over the two cocksfoot cultivars (Table 2). Flecha outyielded any other cultivar while showing the same, top-ranking persistence as the completely summer-dormant cocksfoot Kasbah (Table 2). The non-dormant cocksfoot Jana displayed the lowest mean persistence (Table 2). On the whole, the mean performance of species agreed with results by Nie et al. (2008) and Reed (1996) for Australian environments indicating the higher DM yield and the slight trend towards greater persistence of tall fescue relative to cocksfoot. The joint regression model did not fit adequately GL interaction effects for DM yield or final row cover, as indicated by the lack of variation among genotype regressions (Table 3). The AMMI model including one GL interaction PC axis (AMMI-1) was adequate for both variables. Another adequate model for DM yield was factorial regression of genotype responses as a function of spring–summer (April–September) drought stress and late-spring (May–June) daily maximum temperatures of locations. This model,
compared with AMMI-1, was slightly less accurate (about 71% vs. 76% of GL interaction variation accounted for) but more parsimonious (6 vs. 7 GL interaction degrees of freedom) and, on the whole, more predictive according to the criterion based on the sum of the estimated variances of relevant GL interaction components (sum of two variance components for the two-covariate factorial regression model = 6.22; variance component for AMMI-1 = 2.82). The twocovariate factorial regression model including mean annual water available and absolute minimum temperature of locations was adequate for final row cover, for which it tended towards somewhat greater predictive ability than AMMI-1 when comparing the estimated variances of relevant GL interaction components for these models (2.05 vs. 1.75). Factorial regression models offered the further advantage relative to AMMI-1 of a straightforward extension of results to non-test locations as a function of site values of the relevant environmental variables. Flecha displayed positive GL interaction for DM yield in locations with greater spring–summer (April–September) drought stress (regression slope > 0), whereas Jana had relatively better yield response in less stressing sites (regression slope < 0; Table 4). In substantial agreement with this result, GL interaction for final row cover was positive in sites with less annual rainfall for Flecha and in wetter sites for Jana (Table 4). Also Kasbah exhibited relatively better persistence in drier locations (Table 4). With respect to temperature patterns, Flecha showed positive GL interaction for DM yield in cooler sites in late spring, and Jana relatively better persistence in sites with lower absolute minimum temperature (Table 4). Kasbah was better adapted to warmer sites, as indicated by relatively better yield under higher late-spring temperatures and better persistence under milder winters (Table 4). The expected best-yielding cultivars based on factorial regression modelling as a function of covariate values in the range of test site values are reported in Fig. 1. The tall fescue cultivar Flecha tended to outyield any other cultivar in environments with high drought stress or fairly cool late spring. The south-European cultivars Centurion of tall fescue and Jana of cocksfoot emerged among the top-yielding genotypes under moderate drought stress and high late-spring temperatures. Kasbah was among the topyielding genotypes only under highest late-spring temperatures (32 ◦ C) combined with intermediate drought stress (Fig. 1).
Table 3 Analysis of variance for three-year dry matter yield and final row cover of two cocksfoot and two tall fescue cultivars grown in six locations. Cultivar × location interaction partitioned by (a) species and cultivar within species factors, (b) joint regression, (c) additive main effects and multiplicative interaction, and (d) factorial regression modelling. Source of variation
Degrees of freedom
Cultivar (a) Species Cultivar (Species) Location Cultivar × Location (a) Species × Location Cultivar (Species) × Location (b) Heterogeneity of regressions Deviations from regression (c) PC 1 Residual (d) April–September drought stressb May–June max. daily temperatures Residual Annual water available Annual absolute min. temperature Residual Pooled error
3 1 2 5 15 5 10 3 12 7 8 3 3 9 3 3 9 54
a b * **
Mean squarea Dry matter yield
Final row cover
510.76** 1364.48** 83.90** 625.30** 46.97** 89.82** 25.55** 63.44 NS 42.86** 76.10** 21.49* 86.97** 79.15** 22.91* – – – 8.41
2118.8** 574.1** 2891.2** 5372.2** 738.0** 566.6** 823.6** 1007.2 NS 710.3** 1290.6** 254.3 NS – – – 1809.5** 1214.3** 222.0 NS 139.6
NS, not significant. As difference between estimated long-term potential evapotranspiration and actual water available for the crop. Significant at P < 0.05. Significant at P < 0.01.
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Table 4 Parameters for factorial regression modelling of cultivar × location interaction for three-year dry matter yield as a function of April–September drought stress (DS) and May–June daily maximum temperatures (MaxT) and for final row cover as a function of annual water available for the crop (AW) and annual absolute minimum temperature (MinT), for four grass cultivars grown in six locations. Cultivar
Jana Kasbah Centurion Flecha a * **
Dry matter yield (t/ha)
Final row cover (%)
Intercept
 DSa
−1.13 −23.08 9.81 14.40
−0.0233 −0.0001 −0.0028 0.0270** *
 MaxT
Intercept
0.604 0.849* −0.284 −1.168**
−70.69 35.88 8.97 25.83
 AW
 MinT **
0.1310 −0.0578* −0.0225 −0.0506*
−2.830** 3.080** −0.755 0.505
As difference between estimated long-term potential evapotranspiration and actual water available for the crop. Different from zero at P < 0.05. Different from zero at P < 0.01.
The picture was partly different when considering the persistence as predicted by factorial regression-modelled final row cover (Fig. 1). Kasbah and Flecha were top-ranking in most environments, especially where winter was milder. Jana and Centurion were among the best-persisting genotypes when winter was colder, with outstanding persistence displayed by Jana in environments also featuring fairly high annual rainfall. The widespread yield advantage of tall fescue over cocksfoot may largely derive from greater growth across autumn and winter (Lelièvre et al., 2011). The cocksfoot Kasbah maximized the drought tolerance and persistence through its complete dormancy trait, but its intrinsically low yield potential that is typical of the cocksfoot subsp. hispanica (Piano et al., 2004) led to lower predicted forage yield than the best-performing tall fescue (Flecha) even under extreme drought stress conditions. The high level of persistence attained by Flecha arose from survival mechanisms other than complete dormancy, such as the deep root system (Lelièvre et al., 2011) and the development of an extensive collar of senescent leaf
sheaths around its young tillers in summer (which could increase tiller survival by reducing transpiration losses: Norton et al., 2006). The fairly deep soil which featured the current environments did not limit the expression of the tall fescue deep root trait and its usefulness as a drought avoidance mechanism. The cocksfoot cultivar Jana outyielded Kasbah under low to medium drought stress, while being less persistent in all conditions but the high-rainfall, cold-prone ones. This adaptive response can be accounted for by the higher plant vigour of subsp. glomerata relative to subsp. hispanica, the lack of summer dormancy, and the selection for responsiveness to supplemental irrigation in a relatively temperate region of Jana (Piano et al., 2004). This cultivar has repeatedly shown wide adaptation across favourable to moderately drought stress conditions compared with other cultivars of subsp. glomerata (Piano et al., 2004; Annicchiarico et al., 2011), suggesting a possible dehydration tolerance trait that would be insufficient and less useful than complete summer dormancy for survival under severe summer drought. The indications on top-performing material in Fig. 1 can be exploited for the site-specific targeting of grass cultivars as a function of the expected values of the relevant climatic variables on the site. A previous study on durum wheat indicated the substantial reliability of factorial regression-based recommendations (Annicchiarico et al., 2006). Forage quality would also be an issue for cultivar recommendations, but the only difference that emerged from the analysis of quality traits across three harvests in Elvas and in Sassari was the higher protein content of cocksfoot over tall fescue (about 15% vs. 13.6%: Porqueddu and Simões, unpublished results). 4. Conclusion
Fig. 1. Best cultivars for three-year dry matter yield and final row cover for different levels of relevant climatic variables in a two-covariate factorial regression model (cultivars are reported in descending rank order, excluding those which are inferior to the top-ranking one at P < 0.10; see Table 4 for factorial regression parameters).
The environmental covariates retained for factorial regressions indicated drought stress (either as spring–summer water deficit or as annual water available for the crop) as the main environmental determinant of cultivar adaptive responses across sites of the western Mediterranean basin, but revealed that also responses to temperature patterns had some bearing on genotype adaptation. The contrasting responses to rainfall and low temperatures of the two cocksfoot cultivars for final row cover, and the differences between cultivars in each species for other regression parameters, highlighted the wide variation for specific-adaptation pattern that may characterize elite cultivars within species and its relevance for species comparison. The generated information can drive the recommendation of grass species and cultivars as a function of known long-term local climatic data. Besides, it can help regional breeding programmes with limited resources available in choosing target species and plant types, taking also account of the predicted increase of drought and late-spring temperatures due to climate change. The expected yield and persistence responses in Fig. 1 suggest that Mediterranean tall fescue has general interest for drought-prone areas. A
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completely summer dormant cocksfoot could also be useful for the same areas, especially the warmer ones, if its persistence could be combined with definitely higher forage yielding ability in the cool season. Acknowledgements This study was funded by the EU FP6 project PERMED (INCO2004-509140). We dedicate this study to the memory of Dr. F. Lelièvre, who co-ordinated the project. We thank Dr. E. De Pauw for estimating site evapotranspiration, and P. Chapon, I. Duarte, A. Khedim, M. Mefti, P. Saba and A. Souihka for excellent technical assistance. References Annicchiarico, P., 2002. Genotype x Environment Interactions: Challenges and Opportunities for Plant Breeding and Cultivar Recommendations. FAO Plant Production and Protection Paper No. 174. FAO, Rome, 115 pp. Annicchiarico, P., 2009. Coping with and exploiting genotype x environment interactions. In: Ceccarelli, S., Guimarães, E.P., Weltzien, E. (Eds.), Plant Breeding and Farmer Participation. FAO, Rome, pp. 519–564. Annicchiarico, P., Bellah, F., Chiari, T., 2006. Repeatable genotype x location interaction and its exploitation by conventional and GIS-based cultivar recommendation for durum wheat in Algeria. Eur. J. Agron. 24, 70–81. Annicchiarico, P., Pecetti, L., Bouzerzour, H., Kallida, R., Khedim, A., Porqueddu, C., Simões, N.M., Volaire, F., Lelièvre, F., 2011. Adaptation of contrasting cocksfoot plant types to agricultural environments across the Mediterranean basin. Environ. Exp. Bot. 74, 82–89. Brancourt-Hulmel, M., Biarnès-Dumoulin, V., Denis, J.B., 1997. Points de repère dans l‘analyse de la stabilité et de l‘interaction génotype-milieu en amélioration des plants. Agronomie 17, 219–246. Denis, J.B., 1988. Two-way analysis using covariates. Statistics 19, 123–132. De Pauw, E., Ghaffari, A., Ghasemi, V., 2004. Agroclimatic zones map of Iran: explanatory notes. Research Report, Natural Resources Management Program. ICARDA, Aleppo, Syria, 44 pp. FAO, 2010. The State of Food and Agriculture. Livestock in the Balance. FAO, Rome, 176 pp. Finlay, K.W., Wilkinson, G.N., 1963. The analysis of adaptation in a plant-breeding programme. Aust. J. Agric. Res. 14, 742–754. Gauch, H.G., 1988. Model selection and validation for yield trials with interaction. Biometrics 44, 705–715. Gauch, H.G., 1992. Statistical Analysis of Regional Yield Trials: AMMI Analysis of Factorial Designs. Elsevier, Amsterdam, 278 pp. Ghesquière, M., Jadas-Hécart, J., 1995. Les fétuques ou le genre Festuca. In: Prosperi, J.-M., Guy, P., Balfourier, F. (Eds.), Ressources Génétiques des Plantes Fourragères et à Gazon. INRA-BRG, Paris, pp. 53–70. IPCC, 2007. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, 2007. Cambridge University Press, Cambridge, UK, 938 pp.
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