Field evaluation of resistance to Colletotrichum truncatum in Lens culinaris, Lens ervoides, and Lens ervoides × Lens culinaris derivatives

Field Crops Research 126 (2012) 145–151

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Field evaluation of resistance to Colletotrichum truncatum in Lens culinaris, Lens ervoides, and Lens ervoides × Lens culinaris derivatives S. Vail ∗ , J.V. Strelioff 1 , A. Tullu, A. Vandenberg Crop Development Centre, 51 Campus Drive, University of Saskatchewan, Saskatoon, SK S7N 0L4, Canada

a r t i c l e

i n f o

Article history: Received 8 April 2011 Received in revised form 4 October 2011 Accepted 4 October 2011 Keywords: Lentil Anthracnose Interspecific

a b s t r a c t Anthracnose, caused by Colletotrichum truncatum, is a major disease of lentil (Lens culinaris Medik.). Resistance to the more virulent race Ct0 of the pathogen is extremely rare within the cultivated L. culinaris gene pool and is limited to partial resistance. The secondary gene pool of L. culinaris, especially Lens ervoides, is a source of resistance. Previously, a population of interspecific recombinant inbred lines was developed between susceptible L. culinaris line Eston and resistant L. ervoides L-01-827A; both resistant and susceptible stable lines were then identified in the population. A multi-year field trial in two different disease nurseries was conducted with the objectives of assessing relative resistance levels in the field and to evaluate the usefulness of field-nurseries for selecting resistance. A sub-set of the interspecific lines and L. culinaris and L. ervoides lines were evaluated which included eight resistant, eight partially resistant and four susceptible lines using a randomized complete block design with four replications per site over two years. Results confirm that disease control can be obtained using L. ervoides-derived resistance gene(s) as under high disease pressure, some interspecific lines were significantly more resistant than the most resistant L. culinaris lines. Resistance ratings from disease nurseries were significantly correlated (0.69–0.90) with inoculations of both the virulent race Ct0 of C. truncatum and the less virulent race Ct1 on the interspecific lines suggesting that field nurseries could effectively be used for selecting for resistance within a lentil breeding program. © 2011 Elsevier B.V. All rights reserved.

1. Introduction In the past three decades, world-wide production of lentil has almost tripled with 3.5 Mt production in 2008 (FAO, 2008). With increasing interest in the crop, disease is expected to continue as a major barrier to yield and product quality. In particular, anthracnose caused by Colletotrichum truncatum (Schwein.) Andrus & W.D. can cause significant yield loss and reduction of lentil seed quality on the Canadian prairies and the northern plains of the USA (Chongo and Bernier, 2000a,b), especially if excessive moisture in late summer prolongs growth and delays harvest (Morrall et al., 2008). Yield losses of up to 28 and 57% on resistant and susceptible lines, respectively, can occur under high disease pressure without the application of fungicide (Chongo et al., 1999).

Abbreviations: RIL, recombinant inbred line; NSF, North Seed Farm; rAUDPC, relative area under the disease progress curve. ∗ Corresponding author. Present address: Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N 0X2, Canada. Fax: +1 306 956 7247. E-mail address: [email protected] (S. Vail). 1 Present address: Bayer CropScience, Box 117 Site 600, R.R.#6, Saskatoon, SK S7K 3J9, Canada. 0378-4290/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.fcr.2011.10.002

Survival of the pathogen is aided by the development of microsclerotia that remain in the field after harvest (Buchwaldt et al., 1996). Symptoms of anthracnose initially appear as superficial lesions on young stems and leaves; when the crop reaches the early flowering stage, premature leaflet abscission on lower leaflets occurs. Given adequate rainfall, conidia form in acervuli on stems and abscised leaflets and are splash-dispersed to uninfected tissue causing stem lesions to gradually move up the stem. Enlarging lesions can girdle stems and cause plants to wilt and die (Buchwaldt et al., 1996). Two races of C. truncatum were identified (Buchwaldt et al., 2004) by using a host differential set of eight accessions to characterize 50 isolates of C. truncatum from Manitoba and Saskatchewan. Isolates designated as race Ct1 were avirulent on seven differentials whereas isolates designated race Ct0 were virulent on all differentials. Consequently, race Ct1 is considered less virulent than Ct0, however races were found in equal proportions in the field (Buchwaldt et al., 2004). Breeding for resistance in lentil to C. truncatum, especially to the highly virulent race Ct0, is of great importance. Resistance to Ct1 within the Lens culinaris primary gene pool is abundant; however, resistance to race Ct0 is limited. Resistance to race Ct1 from the cultivar Indianhead, thought to be conferred by a single recessive gene (Buchwaldt et al., 2001),

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has been effectively transferred into cultivars such as CDC Robin (Vandenberg et al., 2002) and CDC Redberry (Vandenberg et al., 2006). However, few cultivars or land races of L. culinaris have been identified with resistance to Ct0. Plant Gene Resources Canada screened more than 1700 accessions from the Vavilov Institute and identified VIR421, collected in Afghanistan by Barulina (1930), with partial resistance (Buchwaldt and Diederichsen, 2004; Vail and Vandenberg, 2010). Breeding lines from the cross 3155S have also demonstrated moderate resistance (Vail and Vandenberg, 2010); these F2:3 family selections from the cross Yerli Kirmizi (‘local red’, a landrace grown extensively in Turkey)/CDC Redberry//CDC Redberry were identified in an anthracnose disease nursery in 2005 and were developed using a form of cyclical recurrent selection to enhance germplasm for minor resistance genes to anthracnose (Muehlbauer et al., 2009). Wild relatives of crop species have been a valuable source of resistance in many pathosystems (Hajjar and Hodgkin, 2007). Lens species in the secondary gene pool of cultivated lentil show resistance to race Ct0 and race Ct1 in both greenhouse and field experiments (Tullu et al., 2006). These include lines of L. ervoides (greatest frequency of resistance), L. lamottei, and L. nigricans. The resistant plant L-01-827A, a selection from L. orientalis, accession PI 72847 but morphologically resembling L. ervoides with respect to leaflet number and morphology, flower size and seed diameter as described by Fiala et al. (2009), was successfully crossed with L. culinaris cultivar Eston, a small seeded, yellow cotyledon, green seed coat, early maturing line released in Canada in 1980 (Slinkard, 1981). Eston is susceptible to anthracnose. This interspecific population, called LR59, was developed. LR59 included 85 stable F7:8 lines (Fiala et al., 2009). Investigation of resistance of LR59 recombinant inbred lines (RILs) to each C. truncatum race indicates the trait is controlled by major genes and when the RIL LR59-81 was crossed with L. culinaris, resistance was shown to be dominant (Fiala et al., 2009; Vail and Vandenberg, 2011). Resistance in LR59 lines had not yet been tested under field conditions. In the current study, field characterization for resistance to C. truncatum in LR59 RILs and select lines of L. culinaris and L. ervoides was performed across two sites and two growing seasons. The objectives were to determine the potential usefulness of the resistance genes from L. ervoides accession L-01-827A and to compare the level of resistance with other sources of resistance found in L. ervoides and L. culinaris, as well to evaluate the utility of nursery screening for interspecific-derived resistance. The hypothesis was that interspecific-derived field resistance would be greater than that found within L. culinaris and that differentiation between resistant and susceptible lines would be possible under field nursery conditions.

2. Materials and methods 2.1. Plant materials Thirty lentil lines were evaluated at two sites in the 2006 and 2007 growing seasons. Fourteen F7:9 RILs and the parent lines from the interspecific cross Eston/L-01-827A (LR59) with differing levels of resistance to race Ct0 and race Ct1 (Table 1; Fiala et al., 2009) were assessed. Also included were four F2:4 (2006) or F2:5 (2007) families from the cross 3155S (as shown in Table 1) along with the parents, CDC Redberry and Yerli Kirmizi. Resistant and susceptible L. culinaris checks were also included to link the results to previous research on anthracnose resistance in lentil. The susceptible check Pardina, a Spanish landrace grown in both Spain and the Palouse area of the north-western USA, has been used as a universal susceptible check for both ascochyta blight and anthracnose for many years. Partially resistant lines CDC Robin

(Vandenberg et al., 2002), VIR421 (Buchwaldt and Diederichsen, 2004), and the cultivar Indianhead were also included along with four additional accessions of L. ervoides (PI 72815 from Turkey, PI 72659 from Syria, and from unknown origin PI 72503 and PI 116015) selected based on previous reports of varying anthracnose resistance (Tullu et al., 2006). The L. ervoides accessions were all part of the core collection obtained from the International Center for Agricultural Research in the Dry Areas, Syria. As the various lines evaluated were not consistent in their adaptation, yield data was not collected for any of the plots. 2.2. Disease nurseries, experimental design, and disease inoculation Both sites for the field experiments were located in Saskatoon, Saskatchewan, at the North Seed Farm (NSF) and Preston Farm of the Department of Plant Sciences, University of Saskatchewan. The soil type of both sites is Dark Brown Chernozemic with the NSF being a fine sandy loam to loam texture (Bradwell Elstow association) and the Preston site being silt loam texture (Elstow Hanley association). The Preston site is located approximately 2 km of the NSF. The NSF site is an established lentil disease nursery; lentil breeding lines have been inoculated with the previous year’s infested lentil stubble for more than 12 years and it is expected the established pathogen population consist of both races of C. truncatum. The NSF was seeded on May 25 in 2006 and May 17 in 2007. The seeding date of the Preston site was June 2 in both years, deliberately delayed to create a contrasting environmental effect based on precipitation pattern and crop development. The plots were arranged as a randomized complete block design with four replications per site each year. Plots were single rows, 75 cm long and with 30 cm between rows, with 20 seeds per plot planted approximately 2.5 cm deep with a row cone drill. Each plot was flanked with rows of both Eston (susceptible to both races) and CDC Redberry (resistant to Ct1 and susceptible to Ct0). Plots were inoculated July 4 in 2006 and June 29 in 2007 with diseased lentil straw collected from the NSF anthracnose nursery the previous year. Misting irrigation was used to promote disease development and commenced at the time of inoculation when the plants were in the late vegetative to early flowering phase at the NSF and were mid-vegetative at the Preston site. Irrigation was continued till the first week of August or mid-August at the NSF and Preston sites, respectively. At the NSF, overhead sprinkler irrigation with a spray diameter of 18.29 m with risers spaced for no watering overlap was applied at dusk for 15 min. Water pressure was 60 psi applying approximately 0.01 mL/mm2 over the daily irrigation period. At the Preston site, a misting irrigation system using Micro-BirdTM II Spinner SP16-340 (RainBird, CA) spaced 3.66 m apart ran for 15 min in the evening, twice overnight and early morning at 40 psi applying 0.01 mL/mm2 per night. Each replication at all sites was surrounded by four rows of barley to prolong canopy wetness throughout the day. 2.3. Disease evaluation and analysis Whole plots were rated once a week throughout the epidemics, starting July 18 and July 25 in 2006 at the NSF and Preston sites for a duration of 38 and 48 days, respectively. In 2007, ratings started July 13 and July 23 at NSF and Preston, respectively both for a duration of 22 days (Fig. 1). The Horsfall and Barratt (1945) scale was used to obtain percentage grade values for the amount of plant tissue infected with disease. This scale is based on grades of disease that differ by a factor of two either side of 50% diseased tissue. The theory underlying the grades is that the human eye distinguishes diseased or disease-free tissue according to the logarithm

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Table 1 Relative area under disease progress curves (rAUDPC) for lines of lentil evaluated in anthracnose nurseries at the North Seed Farm (NSF) and Preston sites in the 2006 and 2007 growing seasons. Line

Species

Controlled condition screeninga Ct1

LR59 interspecific recombinant inbred lines Le × Lc RILc HS LR59-25 LR59-31 Le × Lc RIL HS LR59-33 Le × Lc RIL HS LR59-36 Le × Lc RIL MS LR59-38 Le × Lc RIL R LR59-54 Le × Lc RIL R Le × Lc RIL MS LR59-76 Le × Lc RIL MR LR59-80 Le × Lc RIL R LR59-81 Le × Lc RIL R LR59-87 HS LR59-91 Le × Lc RIL Le × Lc RIL HS LR59-105 HS LR59-132 Le × Lc RIL Le × Lc RIL HS LR59-133 Commercial lentil cultivars Lc Yerli Kirmizi Lc Eston Lc Indianhead Lc Pardina Lc CDC Redberry CDC Robin Lc VIR421 Lc Lentil breeding lines Lc F4 or F5 d 3155S-1 3155S-5 Lc F4 or F5 Lc F4 or F5 3155S-6 3155S-8 Lc F4 or F5 Lens ervoides accessions Le PI 72570-3 PI 116015 Le Le PI72659 L-01-827A Le PI 72815 Le a b c d

2006

2007

Ct0

NSFb

S HS HS R R R MS R R R HS S HS MR

49.2 79.4 66.3 18.6 24.9 48.3 55.6 59.9 39.7 32.5 72.2 68.6 73.6 73.7

HIJK ABC CDEFG MN LMN HIJK GHIJ DEFGH JKL KLM BCDEFG BCDEFG BCDEF BCDE

36.4 47.4 39.3 10.9 10.9 15.8 14.2 21.0 20.5 1.8 45.1 46.5 43.3 43.3

EFG C DEF NO NO LMN MN JKLM KLM P CD CD CDE CDE

5.2 31.4 8.6 1.8 1.8 3.1 5.7 4.5 2.9 2.0 9.9 11.2 22.9 18.5

FGHIJK C FGHIJK JK K GHIJK FGHIJK FGHIJK HIJK IJK FGHI EF D DE

96.3 85.2 63.6 95.7 71.5 75.4 67.8

A AB CDEFGH A BCDEFG BCD CDEFG

79.9 58.8 28.9 74.9 31.1 35.0 31.2

A B GHIJ A GHI FGH GHI

69.5 39.8 9.3 63.2 10.0 17.9 9.5

A B FGHIJ A FGH DE FGH

64.0 56.1 68.6 71.5

CDEFGH FGHIJ BCDEFG BCDEFG

28.0 25.7 21.9 36.4

HIJK IJK JKL EFG

10.4 7.9 10.5 9.6

FG FGHIJK F FGH

42.1 96.3 57.7 39.5 10.5

IJK A EFGHI JKL N

2.9 81.7 14.7 16.8 4.9

P A LMN LMN OP

3.0 70.3 2.7 3.0 3.0

HIJK A HIJK GHIJK GHIJK

Preston

NSF

Preston 1.1 4.2 3.4 2.5 1.7 0.9 1.7 1.1 0.7 2.0 2.3 3.6 3.2 2.0

F DEF DEF DEF DEF F DEF F F DEF DEF DEF DEF DEF

17.8 9.0 4.0 16.9 3.7 6.2 3.5

B C DEF B DEF CDE DEF

4.0 4.8 6.2 4.3 1.5 22.7 2.1 1.3 2.2

DEF CDEF CD DEF EF A DEF F DEF

As determined by Fiala et al. (2009) using the rating scale described by Buchwaldt et al. (2004). Means within sites each year that are not followed by the same letter are significantly different (P < 0.05). Lens ervoides accession L01-827A × Lens culinaris accession Eston recombinant inbred lines (RILs). Yerli Kirmizi/CDC Redberry//CDC Redberry F2:4 (in 2006) or F2:5 (in 2007).

of light intensity. Percentage grade values were converted to Area Under the Disease Progress Curve (AUDPC) values to quantify disease progression over time where average percent between two adjacently timed ratings was multiplied by the number of days between when ratings were evaluated (Shaner and Finney, 1977). To compare different sites and years, AUDPC values were converted to relative AUDPC (rAUDPC) by dividing by the duration of the epidemic and multiplying the outcome by 100 as described by Shtienberg et al. (2000). Values were analyzed as a combined experiment in the Mixed procedure in SAS (SAS Institute, Cary, NC) in a model where all factors were considered random (site, year, replication within each site and year, and all interactions) except for Line, which was considered a fixed effect. The disease ratings of the flanking resistant and susceptible check plots were added to the statistical model as resistant and susceptible covariates to adjust for within-block variability. Separate analyses by year and by each site within each year were performed for all lines as well as individual groups of lines (from the cross 3155S, L. culinaris, L. ervoides, and L. culinaris × L. ervoides RILs) using the Mixed procedure. Values for least square means were calculated independently within each site by year combination. Standard errors of differences and P-values for differences between pairs of means of different lines were calculated using the PDIFF option in SAS and significant pair-wise differences were converted to letter groupings (Saxton, 1998).

For the set of lines that were common to previous controlled condition experiments performed in growth chambers by Fiala et al. (2009), Pearson correlation coefficients were calculated in SAS for average field disease ratings and previous ratings (converted to numerical grades of 1–6 for the different disease classes) which were inoculated separately with both races of the pathogen (Table 1; Fiala et al., 2009). 3. Results Disease severity was greater in the 2006 vs. 2007 growing season at both sites. In both years the NSF site had more disease than Preston. As planned, the onset of flowering was delayed, on average, by about two weeks at the Preston site compared to the NSF site due to the difference in seeding dates. For example, Eston and Redberry checks started flowering June 30 to July 2 both years at the NSF and not till July 11–14 at the Preston site. Similarly, the beginning of the disease epidemic was delayed with the duration being similar to the earlier seeded site. Highly significant differences were observed among lines in both seasons at both sites; covariates were highly significant and greatly reduced the contribution of the site years to overall variability (Table 2). When all L. culinaris lines were considered, the ratings in 2006 separated them into two groups (Table 1). Moderate resistance was observed in the group of cultivars classified as resistant to race

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2006 100

40

90

35

80 30 25

60 50

20

40

15

30

Air Temperature (oC)

Rainfall (mm)

70

10 20 5

10 0

0

2007 40

100 90

35

80

Rainfall (mm)

25

60 50

20

40

15

30

Air Temperature (oC)

30 70

10 20 5

10 0

0

Total Precip

Max Temp

Fig. 1. Weather data for Saskatoon: natural rainfall and maximum temperature; the brackets indicate the period of the epidemic. Note: Solid bracket indicates epidemic at the North Seed Farm and the dotted bracket the Preston site. Source: Environment Canada, National Climate Data and Information Archive.

Ct1 (Indianhead, CDC Redberry and CDC Robin) compared to susceptible cultivars (Eston, Pardina, and Yerli Kirmizi) under modest disease pressure. The accession VIR421, identified by Plant Gene Resources Canada as having some resistance to race Ct0, had field resistance similar to other L. culinaris lines previously established as race Ct1 resistant. Limited improvement in field resistance for families from the 3155S cross was observed compared to the recurrent parent CDC Redberry. A small but significant improvement in the family 3155S-5 over the race Ct1 resistant line CDC Robin was observed except in 2007 at the Preston site (Table 1). Minimal differences among the four families of the 3155S cross were observed overall (Table 1). When representative lines from each of the groups were compared (Table 1), the resistant LR59 RILs had significantly greater resistance than the most resistant L. culinaris lines (3155S-5, VIR421, and CDC Redberry) which was especially evident under greater disease pressure (NSF 2006). LR59-36 had significantly less disease than the most resistant 3155S family (-5) as well as Ct1 resistant and susceptible lines. Another RIL, LR59-81, had disease levels similar to 3155S-5. Between the two resistant

L. ervoides lines, significant differences were seen with less disease on PI 72815 than the LR59 parent L-01-827A (Table 1). Differences in anthracnose ratings between lines from the LR59 population were most evident under the higher disease pressure in 2006 as compared to 2007 (Tables 1 and 3). Some lines from the LR59 population (LR59-36, -38, -87, -81, -54, -76, and -80) demonstrated high resistance, similar to the L. ervoides parent L-01-827A. The susceptible RILs (LR59-31, -133, -132, and -91) had ratings similar to the susceptible parent Eston (Table 1). Similar to reports from controlled conditions (Fiala et al., 2009), transgressive segregants for resistance or susceptibility were observed in the field for the LR59 population. rAUDPCs at each site in each year were significantly correlated with average ratings from controlled condition screening performed by Fiala et al. (2009) (Table 3). Best correlation to screening under controlled conditions with both races was found in 2006 at the Preston site which exerted the second greatest disease pressure on the lines. Disease nursery conditions with the greatest disease pressure showed only a slightly higher correlation than low disease pressure. However, the lack of disease pressure in 2007 at the Preston site resulted in no differentiation of

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Table 2 Mixed model analysis of variance of disease ratings on lentil lines evaluated in anthracnose disease nurseries in the 2006 and 2007 growing seasons. Source of variation Combined Line Susceptible covariate Resistant covariate Year Site Year × site Block (year × site) Year × line Site × line Year × site × line Residual 2006 Line Susceptible covariate Resistant covariate Site Block (site) Site × line Residual 2007 Line Susceptible covariate Resistant covariate Site Block (site) Site × line Residual 2006 North Seed Farm Line Susceptible covariate Resistant covariate Block Residual 2006 Preston Line Susceptible covariate Resistant covariate Block Residual 2007 North Seed Farm Line Susceptible covariate Resistant covariate Block Residual 2007 Preston Line Susceptible covariate Resistant covariate Block Residual

Numerator degrees of freedom

Denominator degrees of freedom

F-Value

P

29 1 1

29.6 344 279

6.52 38.86 61.82

<0.01 <0.01 <0.01

Estimate

0 0 0 0 353,323 0 711,941 533,114 29 1 1

29.4 199 206

14.46 12.54 23.04

<0.01 <0.01 <0.01 0 0 383,158 856,836

29 1 1

29 81.6 107

2.85 10.06 0.23

<0.01 <0.01 0.63 125,187 307 1,030,608 191,417

29 1 1

13.32 1.39 0.60

85.3 68 39

<0.01 0.24 0.44 7311 1,425,239

29 1 1

86 86 86

58.49 10.54 18.71

<0.01 <0.01 <0.01 0 293,518

29 1 1

88 88 88

56.92 1.42 0.06

<0.01 0.24 0.81 0 268,521

29 1 1

83 59.5 69.8

10.22 8.52 1.15

<0.01 <0.01 0.29 1212 107,128

resistance in the interspecific RILs (Table 1). Field testing in the disease nurseries was equally correlated to results when inoculated with both races suggesting field conditions could effectively screen for resistance to both races of C. truncatum (Table 3).

4. Discussion The greater disease severity in the 2006 vs. 2007 growing season was most likely due to more consistent rainfall after inoculation in 2006, which would have promoted fungal growth as well as spread

Table 3 Correlations between relative area under disease progress curve values from field experiments and data from controlled condition testing done by Fiala et al. (2009) of 14 interspecific RIL lines inoculated with race Ct1 and race Ct0 of Colletotrichum truncatum. Race Ct1

Race Ct0 a

Average North Seed Farm 2006 Preston 2006 North Seed Farm 2007 Preston 2007 a

Pearson correlation coefficient.

Correlation

P

Correlationa

P

0.85 0.76 0.90 0.70 0.69

<0.01 <0.01 <0.01 <0.01 <0.01

0.81 0.75 0.84 0.66 0.71

<0.01 <0.01 <0.01 <0.01 <0.01

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of conidia by rain-splash. Higher temperatures in August also prolonged the anthracnose epidemic in 2006; temperatures dropped below optimal (20–24 ◦ C) for disease development (Chongo and Bernier, 2000a,b) in August of 2007 (Fig. 1). In both years, the NSF site, which is believed to have more soil-borne inoculums because of a much longer history of anthracnose inoculation activity, had more disease than Preston. The delayed onset of flowering, by about two weeks at the Preston site compared to the NSF site, may have also contributed to reduced disease as resistance declines at the onset of flowering (Chongo and Bernier, 2000a). Field evaluation of newly identified L. culinaris lines with partial resistance to race Ct0 (families from the cross 3155S and VIR421) showed limited improvement of resistance over currently grown lines. Based on observations in the anthracnose nursery in 2005 (data not shown), families from cross 3155S were expected to show improved resistance over commercially available partially resistant lines. Instead, only one family showed significant improvement over the race Ct1 resistant line CDC Robin (Table 1). Yerli Kirmizi proved highly susceptible (Table 1), demonstrating that its contribution to the resistance observed in cross 3155S families is minimal and possibly limited to minor genes or downstream defence related pathways triggered by resistance genes in CDC Redberry. The small sub-sample (four of approximately 75 3155S F2:3 families) may have failed to capture the variability in the larger original population. Furthermore, susceptibility within each of the families would have been selected against in the growing season of 2005 when originally grown at the NSF under disease pressure. The partial resistance exhibited by cross 3155S families and VIR421 will be useful in creating resistant lines providing resistance is not linked to deleterious traits that would negatively impact yield potential. Positive effects of partial resistance to anthracnose on reducing yield loss are evident under high disease pressure; however, under low to moderate anthracnose pressure, as observed in the 2007 growing season of this study, partial resistance offered no benefit or detriment over susceptible cultivars. Select interspecific RILs showed better resistance than what is currently available in registered cultivars, indicating this source of resistance could be effectively used to reduce the incidence and severity of anthracnose in lentil crops in Saskatchewan. The L. ervoides accession PI 72815 had significantly less disease than the resistant parent L-01-827A (Table 1). This is consistent with average ratings of Tullu et al. (2006), who found PI 78215 to be one of the most resistant L. ervoides accessions. Interspecific RILs have been generated from a cross of PI 72815 and Eston with the aim of transferring resistance genes from the wild accession PI 72815 to L. culinaris (unpublished data). Highly significant correlations between disease ratings at all sites over both years and ratings under controlled conditions suggests that field evaluations of resistance accurately reflect resistance to both races in this population even under lower disease pressure. Chongo and Bernier (1999) reported significant correlations between field inoculations and disease screening under controlled conditions for various components of partial resistance. Given that resistance derived from L-01-827A is either controlled by the same gene(s) or by genes that are tightly linked (Vail and Vandenberg, 2011), the fact that results observed in this study of field inoculations with a population of Mixed races correspond with data from controlled condition inoculations with individual races (Fiala et al., 2009) is not surprising. These results confirm that selection for resistance in segregating populations, where L. ervoides line L-01-827A has been used as a source of resistance, can effectively be performed using field disease nurseries. Selection for resistance derived from L-01-827A based on single plants at the F2 and F3 is now regularly employed at the NSF. The results presented here indicate that single plant selections may be effective; however the presence of resistance should be assessed in

later generations when replicated trials and controlled condition screening experiments are possible. Additionally, special consideration should be given to populations that are selected in years with lower disease pressure. Chongo and Bernier (1999) suggest that AUDPC values from the field are useful for comparing and selecting resistant lines, but suggested more than two years of testing may be required when evaluating components of partial resistance under field conditions. Currently, advanced trial entries are screened for race Ct1 resistance in replicated experiments under controlled conditions. As breeding lines with L. ervoides-derived resistance genes near the latter portion of the breeding cycle, controlled condition screening with race Ct0 may be useful for selecting potential varieties between various families and for selecting breeder seed lines within the selected families. Breeding for resistance to the highly virulent race Ct0 of C. truncatum is of the utmost importance for lentil production in Canada and the USA. Overall, L. ervoides-derived resistance to anthracnose demonstrated the highest level of field resistance in this study, especially under higher disease pressure. Usefulness of the introgressed resistance genes appears most evident in seasons conducive to anthracnose development. Based on these results, selection for resistant plants from F2 disease nurseries should be complemented with controlled condition testing at another generation because field seasons with non-conducive conditions for anthracnose may not fully amplify differences. Based on, in part, the results of this study, continued investment into introgression of resistance genes from L. ervoides accession L-01-827A into cultivated lentil was warranted. To further facilitate selection for resistance derived from L. ervoides, molecular markers for the intogressed chromosomal segments containing interspecific-derived resistance is underway using single nucleotide polymorphisms. Acknowledgements Funding was generously provided by the Saskatchewan Pulse Growers and the Robert P. Knowles Scholarship. The authors are extremely grateful for technical assistance provided by B. Barlow, K. Blomquist, S. Ife, T. Prado, and M. Thompson and the editing assistance of G. Binsted. References Barulina, H., 1930. Lentils of the U.S.S.R. and of other countries (English Summary). Bull. Appl. Bot. Genet. Plant Breeding 40, 265–304. Buchwaldt, L., Morrall, R.A.A., Chongo, G., Bernier, C.C., 1996. Windborne dispersal of Colletotrichum truncatum and survival in infested lentil debris. Phytopathology 86, 1193–1198. Buchwaldt, L., Vandenberg, A., Tullu, A., Bernier, C.C., 2001. Genetics of resistance to anthracnose (Colletotrichum truncatum) in lentil. In: Proceedings of the 4th European conference on grain legumes, Cracow, Poland, July 8–12, p. 242. Buchwaldt, L., Anderson, K.L., Morrall, R.A.A., Gossen, B.D., Bernier, C.C., 2004. Identification of lentil germplasm resistant to Colletotrichum truncatum and characterization of two pathogen races. Phytopathology 93, 236–249. Buchwaldt, L., Diederichsen, A., 2004. New disease resistant lentil germplasm identified at Plant Gene Resources of Canada (PGRC). In: Proceedings of the 5th Canadian Pulse Research Workshop, London, Ontario, November 28–30, p. 204. Chongo, G., Bernier, C.C., 1999. Field and growth chamber evaluation of components of partial resistance to Colletotrichum truncatum in lentil. Can. J. Plant Pathol. 21, 58–63. Chongo, G., Bernier, C.C., Buchwaldt, L., 1999. Control of anthracnose in lentil using partial resistance and fungicide applications. Can. J. Plant Pathol. 21, 16–22. Chongo, G., Bernier, C.C., 2000a. Effect of host, inoculum concentration, wetness duration, growth stage and temperature on anthracnose of lentil. Plant Dis. 84, 544–548. Chongo, G., Bernier, C.C., 2000b. Disease incidence, lesion size, and sporulation in Colletotrichum truncatum as influenced by lentil genotype and temperature. Can. J. Plant Pathol. 22, 236–240. Fiala, J.V., Tullu, A., Banniza, S., Séguin-Swartz, G., Vandenberg, A., 2009. Interspecies transfer of resistance to anthracnose in Lentil (Lens culinaris Medic.). Crop Sci. 49, 825–830.

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