Adaptability of peach cultivars [Prunus persica (L.) Batsch] to the climatic conditions of the Ebro Valley, with special focus on fruit quality

Scientia Horticulturae 190 (2015) 149–160

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Adaptability of peach cultivars [Prunus persica (L.) Batsch] to the climatic conditions of the Ebro Valley, with special focus on fruit quality G. Reig a,∗ , S. Alegre a , F. Gatius b , I. Iglesias a a b

IRTA, Parc Científic i Tecnològic Agroalimentari de Lleida, edifici Fruitcentre, E-25003 Lleida, Spain Universitat de Lleida, Departament de Química, Av. Rovira Roure, 191, E-25198 Lleida, Spain

a r t i c l e

i n f o

Article history: Received 14 February 2015 Received in revised form 8 April 2015 Accepted 16 April 2015 Available online 15 May 2015 Keywords: Prunus persica Yield efficiency Fruit quality Antioxidant capacity

a b s t r a c t Adaptability of 89 peach cultivars of distinct origin to climatic conditions of the Ebro Valley at the IRTAExperimental Station of Lleida (Lleida, northern Spain) over three consecutive years (2009–2011) was studied. For this purpose, several agronomic, morphological and internal quality traits of the fruits were evaluated. Agronomic traits included bloom and harvest dates, yield, and yield efficiency, while morphological traits encompassed fruit shape and size, percentage of red skin, and an appearance quality index. The latter was established to facilitate the assessment of each cultivar on the basis of fruit appearance. Internal quality parameters included flesh firmness, soluble solids content, titratable acidity, sensory attributes, and relative antioxidant capacity. Under the climatic conditions of the Ebro Valley, extensive variability was observed for most quantitative and qualitative (breeding program, fruit type and flesh color) traits. In terms of agronomic performance and fruit quality (fruit appearance included), we considered that a well-adapted cultivar for a given area should achieve the following characteristics: high yield efficiency, high appearance index quality, high relative antioxidant capacity, strong flavor, and medium to high ripening index. However, according to the different breeding programs, fruit types, and flesh colors evaluated in this study, none of them simultaneously showed these characteristics. However, some achieved a number of the desired traits. A principal component analysis for melting peach, nectarine, non-melting peach and flat peach cultivars revealed the best ones for each fruit type. The results showed that cultivars do not combine all the desired traits. Nevertheless, these findings are valuable for breeding strategies aiming to achieve cultivars with better adaptation to the climatic conditions of the Ebro Valley. © 2015 Elsevier B.V. All rights reserved.

1. Introduction In the last two decades, many new cultivars from breeding programs worldwide have been introduced into the Spanish peach production system. The use of such cultivars has allowed a longer harvest season (from mid-April to the end of October), improved agronomic performance, and enhanced fruit appearance and quality (Iglesias and Echeverría, 2009; Reig et al., 2012, 2013b). The adoption of the new cultivars, together with the consistent improvement in irrigation, fertilization, crop protection, postharvest technology, and certification and traceability techniques, has

∗ Corresponding author. Present address: Estación Experimental de Aula Dei (CSIC), Departamento de Pomología, Apdo 13034 Zaragoza. Tel.: +34 699461558. E-mail address: [email protected] (G. Reig). http://dx.doi.org/10.1016/j.scienta.2015.04.019 0304-4238/© 2015 Elsevier B.V. All rights reserved.

allowed Spanish growers to increase in competitiveness, in particular with respect to export markets. Indeed, Spain is the third largest peach producer worldwide, surpassed only by China and Italy, the second largest producer in the European Union, and the leader of exports in Europe (FAOSTAT, 2014). The main peach-producing area in Spain lies in the Ebro Valley – which includes regions of Catalonia and Aragon – and accounts for 63% of the total production of this crop in this country (Iglesias et al., 2012). Peach breeding programs aim to improve agronomic performance, external fruit quality (size and appearance), postharvest life, and organoleptic and nutritional traits (Font i Forcada et al., 2014a; Kader, 2002; Monet and Bassi, 2008). However, in recent decades, the adaptability (good agronomic performance, fruit appearance and internal fruit quality) of newly released peach cultivars to different climatic conditions from their country of origin has not been a selection criterion considered by the main breeding programs.

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Significant efforts have been made to test the performance of the new released worldwide peach cultivars in the main peachproducing areas of Europe (Berra et al., 2011; Hilaire, 2003; Hilarie and Giauque, 2003; Iglesias et al., 2012). The knowledge gathered from such research is essential for commercial peach production, as well as for future breeding programs. Indeed, it is vital to characterize the properties of peaches and to quantitatively assess variability among cultivars in order to achieve improved discrimination, enhanced processing efficiency for the peach industry, and assured high quality. However, the collection of precise information about the agronomic performance, appearance, and internal quality traits of fruit is a time-consuming process. Few authors studied some of these traits in several commercial and traditional peach cultivars (Cevallos-Casals et al., 2006; Chalak et al., 2006; Font i Forcada et al., 2014a; Legua et al., 2011; Reig et al., 2013a,b) and in Prunus persica breeding progenies (Abidi et al., 2011; Cantín et al., 2009a,b, 2010). However, no study has simultaneously addressed the variations in the three main characteristics of peach cultivars (agronomic performance, fruit appearance and internal fruit quality) when grown under different climatic conditions to those of their country of origin. Nor has a multidimensional dataset been used to establish a phenotypic relationship among cultivars or variables. In particular, there is a knowledge gap concerning the nature of the relationships between agronomic, morphological, and internal fruit quality traits for peach cultivars. The differences and similarities of these traits depend on the breeding program from which the cultivars derive and the influence of growing conditions. Plant growth and architecture, yield, blooming and harvest time, fruit shape, flesh texture, and flesh color and acidity levels are genetically controlled in breeding programs (Dirlewanger et al., 1999; Infante et al., 2008; Lester et al., 1996; Martínez-García et al., 2013). However, attributes like fruit size, mass, sugar content, and phytochemical content are significantly affected by the growth environment, seasonal factors, and rootstocks (Cantín et al., 2009a; Font i Forcada et al., 2014b; Génard et al., 1994; Schnabel and Crisosto, 2008). To enable comparisons of traits, here we evaluated various peach cultivars grown in the same season and the same region in northern Spain. The aims of this work were: (1) study the adaptability of various peach cultivars by characterizing them on the basis of agronomic performance, fruit appearance, and internal fruit quality traits; (2) examine the effect of origin and pomological characteristics on these traits; (3) apply multivariate analysis to identify the cultivars best adapted to the climatic conditions of the Ebro Valley.

2. Materials and methods 2.1. Plant material Eighty-nine peach cultivars representing a wide range of breeding programs were grown at the IRTA-Experimental Station (Lleida, northern Spain) and subjected to evaluation in the seasons of 2009–2011 (Table 1). In order to simplify identification, the flat peach and flat nectarine cultivars will henceforth be referred to as flat peach cultivars. The four year old trees were grafted onto INRA® GF-677 rootstocks, spaced 4.5 m × 2.5 m and trained to central axis system (893 trees ha−1 ). With this training system the full yield is achieved for most of the cultivars at the fourth year. Each cultivar was replicated on three trees. The rows were oriented from NE to SW. The trees were trickle-irrigated using drip irrigation, with two drips per tree, delivering 4 l of water per hour. Standard commercial management practices recommended for the area were followed; these included fertilization and the control of pests and plant diseases

following the guidelines established for integrated fruit production. The weather conditions for the period 2009–2011 were usual for this continental Mediterranean area: with daily maximum summer temperatures of >30 ◦ C and accumulated annual rainfall of around 370 mm. Hand thinning was carried out in early May in each growing season using similar criteria for all the cultivars in order to obtain similar crop loads. The traits of interest were measured and scored for each cultivar separately over the 3-year period and means of the three years were calculated. The mean value and standard error of each trait for each cultivar are shown in Electronic Supplementary Material (ESM 1–ESM 3). 2.2. Agronomic performance At the end of each season (November), the trunk girth of each tree was measured 20 cm above the graft union. The trunk crosssectional area (TCSA) (cm2 ) was then calculated. Full bloom date (FB) (in Julian days) was recorded following Baggiolini (1952). The harvest date of each cultivar was determined on the basis of flesh firmness, which ranged from 39 N to 49 N. In this study, the harvest season spanned from June to September, covering market demands. Therefore, peach cultivars were classified in three harvest seasons (Table 1): early, mid and late. Fruits from each tree were harvested in a single pick, weighed, and then graded using an electronic grading calibration manager (SAMMO s.r.l., Model S2010, Cesena, Italy) to obtain yield (Y) (kg tree−1 ). Afterwards, yield efficiency (kg cm−2 ) was calculated on the basis of the TCSA obtained for each cultivar and season. 2.3. Fruit appearance Six representative fruits (2 fruits × tree) per cultivar were evaluated and scored according to UPOV (2010) descriptors for Prunus persica L. with slight modifications. Peach dimensions, such as cheek diameter (D), height (H), and suture diameter (W), were measured using a digital caliper (Mitutoyo’s digimatic calliper, Japan) with an accuracy of 0.1 mm. Fruit shape or sphericity was then calculated as H/D and H/W (Cantín et al., 2010; Wert et al., 2007). This trait was not evaluated in flat peaches due to their particular shape. When the ratios were 1, the shape was considered round. Red skin (SC) was visually scored as a percentage of red surface. This trait was not, however, evaluated in non-melting peaches. Symmetry (SY) was calculated as the difference in H between the two cheeks. Stones were characterized by measuring the two principal dimensions of each stone, namely length (SL) and width (SW). Five qualitative traits were recorded. The shape of the pistil end or fruit tip (SPE) was represented by four categories: 1 = pointed, 2 = slightly pointed, 3 = flat, and 4 = depressed. Prominence of suture (POS): 1 = not visible, 2 = weak, 3 = medium, and 4 = strong. Presence of lenticels (POL):1 = not visible, 2 = slightly visible, 3 = visible, and 4 = highly visible. Stone adherence: 1 = freestone within the space between the mesocarp and endocarp (FEW), 2 = freestone with no space between the mesocarp and endocarp (FEO), 3 = semiclingstone (SCL), and 4 = clingstone (CL). Flesh color: 1 = yellow (YL), 2 = yellow-red (YR), 3 = white (WH), and 4 = white-red (WR). SPE was not evaluated in flat peaches, and POS was evaluated only in nectarines. Appearance is the trait that most attracts consumers when purchasing fruit. Markets, and therefore fruit growers, need to achieve cultivars with optimum performance in terms of fruit appearance: round shapes without protruding tips and/or sutures, and without or with only slightly visible lenticels on the skin surface (Badenes et al., 2006; Byrne et al., 2012; Topp et al., 2008; Wert et al., 2007). Therefore, here we developed a new quality index named

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Table 1 Breeding program, origin, harvest season, fruit type, flesh color, and stone adherence of the cultivars evaluated over three seasons. Cultivar

Label number

Breeding Program

Fruit type

Flesh color

ASF 04-71 ASF 05-25 ASF 05-93 ASF 06-07 ASF 06-88 ASF 06-90 Azurite Big Bel Big Top Catherina Country Sweet Diamond Bright Diamond Ray Donutnice Early Rich Endogust Extreme July Extreme Sweet Feraude Fercluse Ferlot Flatprincess Flatqueen Fullred Grenat Hesse Honey Fire Honey Glo Honey Kist Honey Royale IFF 1182 IFF 1230 IFF 331 IFF 800 IFF 962 IFF 1190 Kewina Latefair Luciana Magique Mesembrine Nectabang Nectabelle Nectabigfer Nectadiva Nectaearly Nectagala Nectalady Nectapi Nectapink Nectaprima Nectareine Nectarjewel Nectarlight Nectarmagie Nectarperla Nectarreve Nectarroyal Nectavanpi NG 4/720 NG-187 Noracila O’Henry Onyx PG 3/1312 PG 3/138 PG 3/719 PI 2/84 Pink Ring Platibelle Platifirst Platifun Rich lady Romea Rose Diamond Subirana

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76

ASF ASF ASF ASF ASF ASF Monteaux-Callet Zaiger Zaiger L. Hough Zaiger Bradford Bradford ASF Zaiger ASF Provedo Provedo INRA INRA INRA ASF ASF ASF Monteaux-Callet U. California Zaiger Zaiger Zaiger Zaiger CRA CRA CRA CRA CRA CRA Zaiger Zaiger PSB Europepinieres INRA ASF ASF ASF ASF ASF ASF ASF ASF ASF ASF ASF ASF ASF ASF ASF ASF ASF ASF Minguzzi Minguzzi PSB G. Merrill Monteaux-Callet Minguzzi Minguzzi Minguzzi Minguzzi CRA INRA INRA INRA Zaiger CRA Bradford Agromillora

FP NE FP NE FP FP MPE NE NE NMP MPE NE NE FP MPE NE MPE MPE NMP NMP NMP FP FP MPE MPE NMP NE NE NE NE NE MPE MPE NE MPE MPE MPE NE NE NE FP NE NE NE NE NE NE NE NE NE NE NE NE NE NE NE NE NE NE NE NE NE MPE MPE MPE MPE MPE NMP FP FP FP FP MPE NMP NE FP

W W W Y W W Y WR YR Y YR Y YR W YR WR YR Y Y Y Y WR W Y Y Y Y Y Y Y WR WR W WR Y Y WR Y Y WR YR Y Y W Y W Y Y Y Y Y YR W W W W W Y Y YR Y YR YR WR Y YR Y Y W W WR W YR Y Y W

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Table 1 (Continued) Cultivar

Label number

Breeding Program

Fruit type

Flesh color

Summersun Summersweet Surprise Sweet Dream Sweetbella Sweetmoon Sweetprim Sweetstar UFO 3 UFO 4 UFO 7 Very Good Zee Lady

77 78 79 80 81 82 83 84 85 86 87 88 89

ARC Zaiger INRA ASF Zaiger ASF ASF ASF CRA CRA CRA ASF Zaiger

NMP MPE MPE MPE MPE MPE MPE MPE FP FP FP MPE MPE

Y WR WR Y WR W WR WR W W Y Y Y

Abbreviations: E, Early (1–10 June); M, Mid (10 June–20 August); L, Late (20 August–30 September); MPE, melting peach; NE, nectarine; NMP, non-melting peach; FP, flat peach; Y, yellow; YR, yellow-red; W, white; WR, white-red; CL, clingstone; FEO, freestone without any space between the mesocarp and endocarp; and FEW, freestone within space between the mesocarp and endocarp.

Table 2 Description of external fruit traits and their value to obtain the appearance quality index (AQI) by fruit type. Trait description

Score

Trait weight Melting peach

Nectarine

Non-melting peach

Flat peach

0.0 0.7 1.0 0.9 0.4 0.2 0.0

3.4

3

5.5

3.8

0.0 0.2 0.6 1.0

3.4

3

–

3.8

0.5 1.0 0.5 0.0

0.5

0.4

0.7

–

0.5 1.0 0.5 0.0

0.5

0.4

0.7

–

0.0 0.3 0.7 1.0

0.9

0.8

1.4

–

1.0 0.7 0.3 0.0

0.6

0.5

0.9

0.6

1.0 0.5 0.0

0.6

5

9.1

0.6

1.0 1.0 0.5 0.0

–

1.5

–

–

1.0 0.5 0.0

–

–

–

1.2

a

D (mm) 90 or + 80/90 73/80 67/73 61/67 56/61 51/56 SC (%) 0–25 25–50 50–75 75–100 H/D (cm) 1.1–1.2 0.9–1.1 0.8–0.9 < 0.8 H/W (cm) 1.1–1.2 0.9–1.1 0.8–0.9 < 0.8 SPE Pointed Slightly pointed Flat Depressed POS Non visible Weak Medium Strong SY (mm) 0–5 5–10 > 10 POL Not visible Slightly visible Visible Highly visible H (mm) 35–44 44–50 > 50

Abbreviations: D, diameter; SC, skin color; H/D and H/W, sphericity; SPE, shape of pistil end; POS, prominence of suture; SY, symmetry; POL, presence of lenticels; and H, height.

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‘appearance quality index’ (AQI) to express all the morphological attributes of the fruit in a single value. The maximum possible AQI score for a given cultivar was 100 points. On the basis of the value of each trait (Table 2), the AQI index was defined as: AQI =

i=n 

(S × W ) × 100

153

and the standard error. Analysis of variance (GLM procedure) was applied using the SAS program package (SAS Institute, 1997). Oneway analysis of variance (ANOVA) followed by Tukey’s honestly significant difference (HSD) test at the P ≤ 0.05 significance level was conducted. Principal component analysis (PCA) was performed using the Unscrambler 7.6 program package (CamoASA, 2001).

i=1

where S was the score for each trait and W was the weight of each fruit type. These scores and weights were defined on the basis of our own experience and that of some of the leading fruit-trading companies in Spain. 2.4. Internal fruit quality traits A total of 18 fruits per cultivar and season (6 fruits × tree) were assessed for flesh firmness (FF), soluble solids content (SSC), and titratable acidity (TA). The FF of two opposing sides (the most and least exposed to light) of each fruit was measured using an 8-mm tip penetrometer fixed in a drill stand (Penefel, Copa-Technology, CTIFL, Saint Etienne du Gres, France). SSC and TA were determined on flesh juice extracted by an automatic juicer (Moulinex, type BKA1). SSC was determined using a digital hand-held refractometer (Atago PR-32, Tokyo, Japan), and the results are given as ◦ Brix. TA was measured with an automatic titrator (Crison GLP 21, Barcelona, Spain) and determined by titrating 10 mL of juice with 0.1 N NaOH to a pH end point of 8.2. The results were expressed as g malic acid L−1 . The ripening index (RI) was then calculated as the SSC:TA ratio. Additionally, all cultivars were subjected to sensory evaluation, as described previously (López et al., 2011; Reig et al., 2013b), by a trained panel of four experts. On the basis of the study by Oraguzie et al. (2009), the panel was set up using the following criteria: (1) membership of the IRTA—Fruit Growing Research Program; (2) at least 3 years of experience in sensory evaluation of stone fruit; and (3) previous participation in a sensory training exercise. The evaluation score sheet contained a continuous scale ranging from 0 to 15 for each attribute and marked with the following three anchors: 0 = lowest level for a specific attribute, except firmness which was 1; 7.5 = medium level for a specific attribute, except sourness which was 8; 15 = highest level for a specific attribute, except firmness which was 14. The following quality attributes were evaluated: “sweetness”, “sourness”, “crispness”, “firmness”, “juiciness”, “fibrousness”, “flavor” and “ease of breakdown”. An overall sensory score from 1 to 10 was used to study the joint influence of all the sensorial attributes, thus representing a fair and indicative value of threshold acceptability for consumers (Konopacka et al., 2010). Six fruits per cultivar and season were used to measure the relative antioxidant capacity (RAC). For this purpose, we used the 2,2-dipyridyl-1,1-diphenyl-2-picrylhydrazyl (DPPH) radical method adapted from Brand-Williams et al. (1995), as described by Cantín et al. (2009a) and Reig et al. (2013b). For RAC determination, fruits were divided into flesh (mesocarp) and peel (exocarp) sections. Three replicates, each using two fruits, were analyzed. The results were expressed in micrograms of Trolox per gram of fresh weight (FW). 2.5. Statistical analysis Three replications for each of the parameters evaluated were used for each cultivar and season. All data were analyzed using both the analysis of variance and multivariate projection techniques. Basic descriptive statistics on all the traits was carried out by calculating the minimum and maximum value, the mean,

3. Results and discussion 3.1. Cultivar influence The minimum and maximum values, means, and standard errors for all the traits and cultivars are listed in Table 3. Great variability among the cultivars was observed. Full bloom (FB) date ranged from 69 to 93 Julian days, recorded mainly in the second half of March. Blooming date is considered a quantitative trait in peach and other Prunus species (Dirlewanger et al., 1999). Thus, the differences for the blooming date were expected. The earliest blooming cultivars were ‘Rose Diamond’ and ‘Summersweet’, and the latest blooming ones ‘Catherina’ and ‘IFF 331’. In Mediterranean areas, early flowering is a desirable trait as it ensures an earlier yield (Fathi et al., 2013). Several field studies on P. persica have shown that early blooming cultivars are more susceptible to spring frost damage (Aygün and San, 2005; Okie et al., 1998). However, at the same phenological stage (stage F) and under controlled conditions in the lab, flowers from early blooming cultivars tend to show less frost damage than mid- and late-blooming cultivars (Reig et al., 2013c). Yield (Y) and therefore yield efficiency (YE), which was calculated based on TCSA (cm2 ), depend on the genetic background of the cultivar (density of flower, fruit set, fruit size and harvest date) and on agronomic and environmental factors (Milatovic´ et al., 2010). However, under the same agronomic and environmental factors, high variability was detected. ‘Nectareine’ and ‘Sweet Dream’ had the highest Y values, while ‘Nectarlight’ and ‘PG 3/1312’ had the highest YE values (Table 3; ESM 1). Regarding morphological traits (Table 3, ESM 1 and 2), great variability was observed. The highest cheek diameter (D) values were recorded on ‘Sweetmoon’, ‘Sweetbella’ and ‘Flatprincess’, all from the ASF breeding program. Fruit shape (H/D and H/W) was evaluated only on round fruits. The highest H/D value (1.0) was for ‘Nectarmagie’ and the highest H/W (1.1) for ‘Very Good’. Fruit shape is an important quality attribute. In this regard, consumers show a preference for round fruits without protruding tips (Cantín et al., 2010). The most symmetrical (SY) cultivars were ‘Platifirst’ and ‘Platifun’, both from the INRA breeding program, and ‘Nectaprima’, which all had SY values of around 4 mm. With the exception of non-melting peaches, 30% of the cultivars had 100% red skin. These cultivars were ‘Azurite’, ‘Early Rich’, ‘Extreme July’, Extreme Sweet’, ‘Sweetbella’, ‘Very Good’ and ‘Zee Lady’ for peaches, ‘ASF 06-07 , ‘Big Bel’, ‘Big Top’, ‘Diamond Ray’, ‘Honey Fire’, ‘Honey Kist’, ‘Honey Royale’, ‘Nectabigfer’, Nectarjewel’ and ‘Nectarmagie’ for nectarines, and ‘Platifun’, ‘ASF 06-90 and ‘Platifirst’ for flat peaches. It has been reported that the skin color (SC) of fruit influences consumer acceptance and sales (Liverani et al., 2002). Indeed, consumers associate intense color with better appearance and quality (Byrne et al., 2012; Iglesias and Echeverría, 2009), and the market demands peaches with more than 80% of SC (Espada et al., 2009). The highest appearance quality indexes (AQIs) were recorded on ‘Big Top’, ‘Onyx’, ‘Azurite’ and ‘Nectabigfer’, and the lowest on ‘Flatprincess’, ‘IFF 1182’, ‘Nectarroyal’ and ‘IFF 331’. The mean values of stone dimensions were 30.4 mm and 25.5 mm for SL and SW, respectively. The highest SL and SW values were for ‘NG197’, ‘IFF 1182’ and ‘Nectarlight’, all nectarines, and the lowest were for ‘Platifun’, ‘Platibelle’ and ‘ASF 06-88’, all three flat peaches. These observations were expected but nevertheless relevant. Successful

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Table 3 Agronomical, morphological, and internal fruit quality traits for 89 commercial peach cultivars subjected to assessment over the seasons of 2009, 2010 and 2011. Minimum, maximum, mean values and standard error (SE) are given for each trait. Trait

Minimum

Maximum

FB (Julian days) Y (kg tree−1 ) YE (kg cm−2 ) D (mm) H/D H/W SY (mm) SC (%) AQI (0–100) SL (mm) SW (mm) Sweetness (0–15) Sourness (0–15) Crispness (0–15) Firmness (1–14) Juiciness (0–15) Fibrousness (0–15) Flavor (0–15) Ease of breakdown (0–15) Overall (0–15) SSC (◦ Brix) TA (g malic acid L−1 ) RI (SSC/TA) RAC flesh (␮g of Trolox g−1 FW) RAC peel (␮g of Trolox g−1 FW)

73 11.2 0.1 56.9 0.8 0.8 4.5 0.0 50.6 13.3 18.2 5.3 7.8 3.2 2.2 3.1 0.8 4.3 3.6 2.8 9.5 2.1 1.1 114.2 127.1

86 56.7 0.8 86.4 1.0 1.1 15.1 100.0 92.1 41.9 31.5 9.4 10.9 10.2 9.6 8.9 6.6 8.9 8.3 7.5 18.6 10.5 6.1 775.3 743.5

Mean ± SE 78.5 ± 0.2 30.7 ± 0.6 0.3 ± 0.0 75.7 ± 0.3 0.9 ± 0.0 0.9 ± 0.0 10.0 ± 3.7 77.0 ± 1.0 72.9 ± 0.4 30.4 ± 0.3 25.5 ± 0.1 7.4 ± 0.1 9.2 ± 0.1 6.2 ± 0.1 5.9 ± 0.1 6.1 ± 0.1 2.0 ± 0.1 7.0 ± 0.1 5.9 ± 0.1 5.0 ± 0.1 12.9 ± 0.1 4.9 ± 0.1 3.2 ± 0.1 408.6 ± 7.8 502.0 + 7.1

Abbreviations: AQI, appearance quality index; FB, full bloom; FF, flesh firmness; D, diameter; H/D and HW, sphericity; RAC, relative antioxidant capacity; RI, ripening index; SC, skin color; SL, stone length; SW, stone width; SSC, soluble solids content; TA, titratable acidity; Y, yield; and YE, yield efficiency.

peach sorting, pitting, and peeling processes require precise characterization of variations in the shape and size of fruit from different cultivars (Li et al., 2014). Sensorial traits varied greatly among cultivars (Table 3; ESM 2 and 3). ‘IFF 331’ and ‘Honey Royale’ were scored as the sweetest, while ‘Onyx’, ‘Honey Kist’ and ‘Early Rich’ were the least sweet. The highest sourness scores were obtained for ‘IFF 1900’ and ‘Hesse’, and the lowest for ‘Very Good’, ‘Ferlot’ and ‘Fercluse’. Regarding crispness, ‘Onyx’, ‘Sweetprim’ and ‘IFF 1182’ were 3-fold crispier than ‘Pink Ring’, ‘UFO 3’ and ‘UFO 4’. Compared to the other cultivars, ‘Big Top’, ‘Nectaearly’ and ‘Nectagala’ were perceived as having the greatest firmness, while ‘Hesse’, ‘Romea’ and ‘IFF 1190’ were the least firm. Consistency and firm textural properties are generally preferred and allow easier handling in postharvest processing (Li et al., 2014). ‘Big Top’, ‘Platibelle’ and ‘Nectabang’ were the juiciest cultivars. Most of the cultivars presented no or very low fibrousness scores, except ‘Rose Diamond’. The highest flavor scores were recorded on ‘Honey Glo’ and ‘Honey Royale’, while ‘Fercluse’, ‘O Henry’ and ‘Ferlot’ had the lowest ones. Regarding ease of breakdown, ‘Honey Royale’, ‘ASF 05-93’ and ‘Mesembrine’ presented the highest scores. Finally, the highest overall scores were for ‘Platifun’, ‘Honey Royale’ and ‘Zee Lady’, while ‘Onyx’, ‘IFF 1230’ and ‘Azurite’ had the lowest. These results are difficult to compare with previously reported sensorial studies of peach because those studies did not report on the sensorial importance of the cultivars. The SSC ranged from 9.5 to 18.6 ◦ Brix (Table 3; ESM 3), which is within the range reported for peach in other studies (Abidi et al., 2011; Cantín et al., 2009b; Font i Forcada et al., 2014b; Legua et al., 2011). All the cultivars showed mean values over 8 ◦ Brix, the minimum value established by the EU for market peaches and nectarines (R-CE no. 1861/2004). Hilaire (2003) proposed that an SSC below 11 ◦ Brix is generally unacceptable to consumers. However, the relationship between the SSC and consumer acceptance is consumer-specific, and there is no single reliable SSC that assures a given percentage of satisfied consumers (Crisosto and Crisosto, 2005; Hilaire, 2003). Twelve percent of the total cultivars evaluated

showed mean SSC values below 11 ◦ Brix. The variability in SSC among the cultivars can be explained by the quantitative behavior of this trait (Dirlewanger et al., 1999). This variability allows the selection of cultivars with a high SSC. In this regard, ‘Nectapink’, ‘Nectarlight’, ‘ASF 05-25’ and ‘Nectalady’ had over 16 ◦ Brix. Following Iglesias and Echeverría (2009), we evaluated cultivars ranging from low acid (<3 g acid malic L−1 ) to high acid (>10 g acid malic L−1 ) content. ‘Platifirst’ and ‘PG 3/719’ showed the lowest TA values, while ‘Diamond Ray’, ‘Donutnice’ and ‘Onyx’ showed the highest ones. RI ranged from 1.1 to 6.1, depending on the SSC and TA of the cultivars. Some authors (Crisosto et al., 2004; Crisosto and Crisosto, 2005; Iglesias and Echeverría, 2009) suggested that RI plays a key role in consumer acceptance of some peach, nectarine, and plum cultivars. Nevertheless, optimal sugar and acid contents for peaches and nectarines are not universal selection criteria and can change depending on the ethnic consumer group involved (Crisosto et al., 2006). In fact, cultivars with improved fruit quality could be achieved by combining these traits with others, such as sensorial ones. The RAC for flesh and peel showed wide variability (Table 3; ESM 3), falling in the range previously reported in P. persica (Abidi et al., 2011; Cantín et al., 2009a; Cevallos-Casals et al., 2006; Reig et al., 2013b). The highest mean RAC values in flesh were for ‘Hesse’ and ‘O Henry’, while ‘Nectarjewel’ and ‘Fercluse’ had the highest mean RAC values in peel. However, the range of RAC in flesh and peel was similar. These results could be attributed to the different distribution of phenolic compounds in skin and flesh per fruit (30% and 70%, respectively) and the high correlation between total phenolics and antioxidant capacity (Abidi et al., 2011; Cantín et al., 2009a; Cevallos-Casals et al., 2006; Vizzotto et al., 2007). Traits such as FB, YE, SC, FF, SSC, TA, RI, and RAC differ among cultivars (Colaric et al., 2005; Font i Forcada et al., 2014a), peach breeding progenies (Cantín et al., 2009a; Abidi et al., 2011), and rootstocks (Font i Forcada et al., 2014b; Orazem et al., 2011). Morphological and sensorial traits also differ between peach cultivars; however, to date, no study has provided a complete description

Table 4 Mean values of agronomic, morphological, and internal fruit quality traits by origin for each fruit type over 2009, 2010 and 2011 seasons. Trait

ASF

CRA

Mounteaux

Zaiger

Nectarine ASF

Bradford

Zaiger

Flat peach ASF

CRA

INRA

3 78.4 46.9 a 0.5 a 66.5 a 78.7 0.9 a 0.9 10.9 ab 87.5 b 73.6 ab 34.2 ab 26.4 7.8 a 9.1 5b 6.3 a 6.6 ab 1.3 b 6.7 6.3 a 5.1 a 11.5 b 2.8 c 4.3 a 424.1 ab 419.4

6 80.3 38.5 ab 0.4 b 62.1 b 77.6 0.8 c 0.9 10.9 ab 87.5 b 72.8 bc 31.5 bc 25.1 7.0 b 9.1 6.5 b 6.6 a 6.6 ab 2.0 ab 7.0 5.3 ab 4.5 ab 12.2 ab 5.3 ab 2.9 bc 414.7 ab 453.4

4 79.5 33.6 b 0.4 b 63.9 ab 76.8 0.9 a 0.8 12.1 a 71.9 c 69.6 c 34.6 a 26.6 7.5 a 9.6 7.1 a 4.6 b 5.1 b 2.6 a 7.4 5.8 a 4.7 a 12.2 ab 6.3 ab 2.7 bc 493.0 a 542.1

3 77.7 38.8 ab 0.2 c 63.5 ab 76.5 0.8 c 0.8 9.7 b 95.8 a 85.6 a 32.5 bc 26.3 6b 9.2 7.9 a 5.9 ab 6.4 ab 1.9 ab 6.6 4.4 b 3.4 b 11.0 b 6.8 a 2.3 c 316.7 b 443.8

7 77.9 34.0 b 0.3 b 63.1 ab 78.5 0.9 a 0.8 11.7 a 96.4 a 78.9 b 31.2 c 25.8 7.1 ab 8.9 6.5 ab 7.3 a 7.2 a 1.6 ab 7.3 5.8 a 5.2 a 12.9 a 5.1 b 3.5 ab 386 ab 457.3

21 77.7 26.5 0.2 63.7 75.0 0.9 0.9 10.9 83.2 b 69.8 b 34.4 26.1 7.7 a 9.2 5.9 b 6.9 a 6.4 1.7 b 7.1 6.3 5.2 13.7 a 4.5 c 3.3 a 387.3 533.9 a

3 76.6 32.7 0.2 62.4 72.0 0.9 0.9 9.9 87.5 b 74.4 b 34.4 27.1 6.6 b 9.2 8.5 a 5.4 b 5.9 3a 8.0 6.2 4.8 11.9 b 8.6 a 1.4 b 368.3 401.6 b

7 78.4 26.2 0.2 63.6 74.9 0.9 0.9 11.2 94.6 a 81.1 a 36.0 27.3 7.4 ab 9.7 6.7 b 6.5 ab 6.4 1.8 b 7.2 6.1 5.1 13.4 a 5.4 b 2.9 a 432.1 433.3 b

7 80.2 a 23.5 0.2 40.2 a 76.5 0.6 a 0.6 a 7.6 a 83.9 a 71.9 a 15.6 a 21.6 8.2 9.6 a 5.1 a 5.2 5.4 2.2 7.0 6.7 5.4 15.0 a 4.3 a 4.5 362.0 526.8

4 76.4 b 29.4 0.2 37.5 b 74.4 0.5 b 0.5 b 6.4 ab 68.7 b 64.2 b 14.3 b 21.3 8.2 9.6 a 3.4 b 5.4 5.8 2.8 7.4 6.0 5.1 12.5 b 2.7 b 4.8 399.9 531.8

77.7 b 26.0 0.2 40.0 a 75.2 0.6 a 0.6 a 5.7 b 84.4 a 75.6 a 14.9 ab 20.8 8.1 9.2 b 4.7 a 6.4 6.4 2.4 7.2 6.8 5.9 12.4 b 3.2 b 4.1 398.0 513.3

G. Reig et al. / Scientia Horticulturae 190 (2015) 149–160

N FB (Julian days) Y (kg tree−1 ) YE (kg cm−2 ) H (mm) D (mm) H/D H/W SY (mm) SC (%) AQI (0-100) SL (mm) SW (mm) Sweetness (0–15) Acidity (0–15) Crispness (0–15) Firmness (1–14) Juiciness (0–15) Fibrousness (0–15) Flavor (0–15) Ease of breakdown (0–15) Overall (0–15) SSC (◦ Brix) TA (g malic acid L−1 ) RI RAC flesh (␮g of Trolox g−1 FW) RAC peel (␮g of Trolox g−1 FW)

Melting peach Minguzzi

Mean separation within rows by Tukey’s test (P ≤ 0.05). In each row by fruit type, values with the same letter are not significantly different. Abbreviations: AQI, appearance quality index; D, diameter; FB, full bloom; FF, flesh firmness; H, height; H/D and H/W, sphericity; RAC, relative antioxidant capacity; RI, ripening index; SC, skin color; SL, stone length; SW, stone width; SSC, soluble solids content; TA, titratable acidity; Y, yield; and YE, yield.

155

156

G. Reig et al. / Scientia Horticulturae 190 (2015) 149–160

Table 5 Influence of horticultural characteristics on the agronomic, morphological and internal fruit quality traits of 89 Prunus persica cultivars. Trait

n FB (Julian days) Y (kg tree−1 ) YE (kg cm−2 ) D (mm) H/D H/W SY (mm) SC (%) AQI (1–100) SL (mm) SW (mm) Sweetness (0–15) Acidity (0–15) Crispness (0–15) Firmness (1–14) Juiciness (0–15) Fibrousness (0–15) Flavor (0–15) Ease of breakdown (0–15) Overall (0–15) SSC (◦ Brix) TA (g malic acid L−1 ) RI RAC flesh (␮g of Trolox g−1 FW) RAC peel (␮g of Trolox g−1 FW)

Fruit type

Flesh color

MPE

NE

FP

NMPE

Y

YR

W

WR

27 78.9 b 37.3 a 0.4 a 77.5 a 0.9 a 0.8 a 11.2 a 88.9 a 76.5 a 32.5 b 25.9 a 7.1 bc 9.2 6.5 a 6.1 ab 6.3 a 2.0 ab 7.0 5.6 b 4.7 b 12.2 c 5.1 a 3.2 b 427.2 b 467.5 b

38 77.6 b 27.0 b 0.2 c 74.7 b 0.9 a 0.9 a 10.7 a 83.5 b 71.8 b 35.1 a 26.8 a 7.4 ab 9.2 6.5 a 6.6 a 6.4 a 1.9 b 7.1 6.0 ab 5.1 ab 13.2 ab 5.3 a 2.9 bc 383.9 b 494.5 b

16 78.6 b 25.8 b 0.2 c 75.1 b 0.5 0.5 b 6.6 c 79.7 b 70.7 b 15.1 c 21.3 b 8.2 a 9.4 4.6 b 5.7 b 5.9 a 2.5 a 7.0 6.5 a 5.4 a 13.6 a 3.6 b 4.4 a 385.6 b 521.5 b

8 81.4 a 34.9 a 0.3 b 75.1 b 0.9 a 0.8 a 9.2 b – 71.3 b 32.3 b 26.4 a 6.8 c 9.0 6.9 a 3.3 c 4.4 b 1.7 b 6.6 5.9 b 4.9 ab 12.9 b 5.5 a 2.5 c 496.3 a 601.7 a

40 78.8 a 31.8 ab 0.3 75.8 ab 0.9 a 0.9 a 10.5 a 68.3 c 73.2 b 33.2 a 26.2 a 7.3 bc 9.3 6.4 ab 5.5 b 5.8 b 1.9 ab 6.9 6.1 ab 5.1 a 12.8 b 5.1 b 3.0 b 429.8 a 520.1 a

12 77.2 b 32.4 a 0.2 74.9 b 0.9 a 0.8 a 10.2 a 90.6 a 77.3 a 32.6 a 26.5 a 7.5 b 9.0 6.1 b 7.0 a 10.0 a 1.5 b 6.9 5.9 b 5.2 a 12.3 b 5.1 b 2.9 b 404.4 ab 432.9 b

22 78.8 a 27.3 b 0.3 75.0 ab 0.7 c 0.7 b 8.8 b 82.4 b 71.7 b 23.7 b 23.1 b 8.0 a 9.4 5.1 c 5.8 b 5.9 b 2.3 a 7.2 6.5 a 5.4 a 13.8 a 4.0 c 3.9 a 398.7 ab 530.7 a

15 78.3 ab 30.9 ab 0.3 77.0 a 0.8 b 0.8 a 10.3 a 81.7 b 70.9 b 31.1 a 26.4 a 6.8 c 9.2 7.2 a 6.3 ab 6.4 ab 2.0 a 7.0 5.1 c 4.2 b 12.7 b 5.9 a 3.2 b 362.2 b 461.2 b

Mean separation within rows by Tukey’s test (P ≤ 0.05). In each row by fruit type and flesh color, values with the same letter are not significantly different. Abbreviations: AQI, appearance quality index; D, diameter; FB, full bloom; FP, flat peach; H/D and H/W, sphericity; MPE, melting peach; NE, nectarine; NMPE, non-melting peach; RAC, relative antioxidant capacity; RI, ripening index; SC, skin color; SL, stone length; SW, stone width; SSC, soluble solids content; TA, titratable acidity; WH, white; WR, white-red; Y, yield; YE, yield efficiency; YL, yellow; and YR, yellow-red.

of these features. Our results provide interesting insights into the dissimilarity of several traits in the various peach cultivars grown under the climatic conditions of the Ebro Valley. Furthermore, a detailed description of three main characteristics of a peach cultivar (agronomic performance, fruit appearance, and internal fruit quality) could be valuable for plant breeders, researchers, technicians, and growers. 3.2. Influence of breeding program The breeding program of each fruit type (melting peach, nectarine, and flat peach) greatly influenced agronomic performance, fruit appearance and internal fruit quality traits. The non-melting peach type was not included in this section due to the limited number of breeding programs; a minimum of three cultivars were required to allow statistical comparison. Minguzzi melting peaches had higher mean Y, YE, H/W and RI values than those from the other breeding programs (Table 4). Y was positively correlated with YE (data not shown), in agreement with Font i Forcada et al. (2014b). Moreover, Minguzzi melting peaches, together with those of CRA, obtained the highest scores for sweetness. Moreover, cultivars from Minguzzi breeding programs, together with those of ASF and Zaiger, obtained the highest scores for firmness. On the other hand, in general, CRA melting peaches presented the highest LS, fibrousness score, and mean RAC flesh values and, together with Mounteaux-Callet peaches, the highest crispness scores. The highest mean SC, AQI and TA values were for Monteuax-Callet melting peaches, while Zaiger melting peaches were juicier than those belonging to the rest of the breeding programs and they also had the highest SSC value. Regarding nectarine breeding programs, firmness and RAC peel values were higher for the ASF breeding program compared to the

others, while Bradford nectarines had the highest crispness and fibrousness scores and highest mean H/W and TA values (Table 4). The highest mean SC and AQI values were for Zaiger nectarines and, together with ASF nectarines, they had the highest SSC values. Finally, ASF flat peaches had significantly higher FB, SY, SSC and TA values than the CRA and INRA flat peaches (Table 4). Moreover, together with the INRA flat peaches, ASF ones presented the highest crispness score and highest mean H/D, H/W, SC and AQI values. Concerning the influence of breeding program on the traits addressed in this study, these differences were expected. In fact, each breeding program focuses on developing the cultivars best adapted to the particular climatic conditions and consumer demands of the given region, thereby implying that not all breeding programs seek the same objectives. Moreover, not all objectives can be achieved when cultivars are grown in areas with distinct climatology to where they were first developed (Reig et al., 2013a). We can therefore conclude that, in terms of agronomic performance and fruit quality (fruit appearance included), a well-adapted peach cultivar must have the following characteristics: high YE, high AQI, high RAC, strong flavor, and medium to high RI. Nevertheless, none of the breeding programs evaluated here presented the full combination of these characteristics. This observation could be explained by the fact that none of the breeding programs in which the cultivars were originally developed involved Mediterranean climatic conditions. 3.3. Influence of horticultural traits Clear differences in agronomic performance, fruit appearance, and internal fruit quality traits were detected between fruit types and flesh colors (Table 5). Melting peaches were more productive than the other fruit types. These differences could be related to

G. Reig et al. / Scientia Horticulturae 190 (2015) 149–160

1.0

157

RAC flesh

63

0.8 0.6

35

88

25

PC 2 (22 %)

0.4 0.2

15

AQI

0.0

89 32

17 84

79 24

33

RI

67 82

81

78 80

64

-0.6

YE

11

66

-0.4

36 18 37

83

73 7

-0.2

RAC peel 65

FLAVOR

-0.8 -1.0

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

PC 1 (35 %) Fig. 1. Segregation of the 27 melting peach cultivars on the basis of yield efficiency (YE), appearance quality index (AQI), relative antioxidant capacity (RAC), flavor, and ripening index (RI). Numbers are used to name cultivars as in Table 1. Italic and underlined numbers represent white flesh and non-italic and non-underlined numbers represent yellow flesh.

lower selection pressure in the case of nectarines and flat peaches because the main breeding programs focused on peach. However, in recent decades there has been high selection pressure for nectarine and very recently also for flat peaches (Reig et al., 2013a). Melting peaches, including white-red fleshed ones, had a greater diameter than the rest of the fruit types (Table 5). The highest SC and AQI values were for melting peaches and yellow-red fleshed fruit. This finding contrasts with those described by Fathi et al. (2013), who reported that white-fleshed fruits show a higher SC than yellowfleshed ones. The highest SSC and the lowest TA mean values were for flat and white-fleshed fruit, in agreement with Ma et al. (2003), who reported that most flat peaches have excellent flavor with a sweet taste, low TA, and high sugar content. Finally, non-melting

peaches and yellow-fleshed fruit showed the highest RAC in flesh, while non-melting peaches and yellow- and white-flesh fruit had the highest RAC in peel. We did not detect a clear trend between white- and yellow-flesh peaches and nectarines in terms of RAC, as reported by Gil et al. (2002). However, when flesh color was divided into four categories (yellow, yellow-red, white, and white-red), a clear trend was observed. Vizzotto et al. (2007) reported that redfleshed peach genotypes selected for high phenolic content have a higher antioxidant capacity than ones with light-colored flesh. Although we found great phenotypic variability among fruit types and flesh colors, we did not identify a single cultivar under the climatic conditions of the Ebro Valley that simultaneously showed high YE, high AQI, high RAC, strong flavor, and medium to high

1.0

AQI 13

0.8

FLAVOR

4

9

28

0.6 8

PC 2 (23 %)

62 60 0.2

YE

29

27 12

16

0.0 -0.2

31

61

-0.4

30

55

57 54

45

39

RAC flesh

38

2

34 42

56

RI

49

50

53 52

40

47

43

46

-0.6

44

51

75

0.4

47 59 RAC peel

-0.8 58

-1.0 -1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

PC 1 (28 %) Fig. 2. Segregation of the 38 nectarine cultivars on the basis of yield efficiency (YE), appearance quality index (AQI), relative antioxidant capacity (RAC), flavor, and ripening index (RI). Numbers are used to name cultivars as in Table 1. Italic and underlined numbers represent white flesh and non-italic and non-underlined numbers represent yellow flesh.

158

G. Reig et al. / Scientia Horticulturae 190 (2015) 149–160

1.0

20

RAC peel

AQI

0.8 RAC flesh

0.6 RI

PC 2 (29 %)

0.4

YE

26

0.2

19

0.0

10 68

-0.2 74

21

77

-0.4 FLAVOR

-0.6 -0.8 -1.0 -1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

PC 1 (46 %) Fig. 3. Segregation of the 8 non-melting peach cultivars on the basis of yield efficiency (YE), appearance quality index (AQI), relative antioxidant capacity (RAC), flavor, and ripening index (RI). Numbers are used to name cultivars as in Table 1.

RI. This observation suggests that further improvement in terms of adaptability is required on the part of breeders.

respectively. Cultivars on the positive side of PC1 had, in general, a higher YE, RI and RAC in peel and a lower AQI than those on the negative side. Cultivars like ‘IFF 331’, ‘PG 3/1312’ and ‘Sweetbella, which are all mid-season harvest cultivars, had high YE, high RI, high RAC in peel and low AQI, while ‘Azurite’, ‘Early Rich’, ‘Onyx’ and ‘Rich Lady’ had the opposite behavior. In contrast, cultivars on the positive side of PC2, such as ‘O Henry’, had, in general, higher RAC in flesh and lower flavor than those on the negative side, such as ‘Onyx’ and ‘Sweet Dream’. For nectarine cultivars, we observed different trends to those shown by melting peach cultivars. PC1 and PC2 explained 28% and 23% of the variance, respectively. No relationship between traits was observed (Fig. 2). This observation could be attributable to the greater phenotypic variability found in this group. The highest RAC

3.4. Principal component analysis A principal component analysis (PCA) was performed in order to evaluate the most important traits considered (YE, AQI, RAC, flavor, and RI). We developed three PCA models for melting peach, nectarine, and flat peach cultivars, respectively, to determine the best cultivars for each fruit type. Both samples and variables were presented jointly and projected onto the plane defined by the first two PCs (Figs. 1–4). The results for melting peach cultivars are presented in Fig. 1. The first two PCs explained 35% and 22% of the variance,

1.0

6

AQI 71

0.8

FLAVOR

0.6

3

1 YE

PC 2 (24 %)

0.4 0.2

86 72

5 69

70 0.0

14

RI

-0.2

76

87

-0.4

RAC peel

23

41

-0.6

RAC flesh 22

-0.8 85 -1.0 -1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

PC 1 (36 %) Fig. 4. Segregation of the 16 flat peach cultivars on the basis of yield efficiency (YE), appearance quality index (AQI), relative antioxidant capacity (RAC), flavor, and ripening index (RI). Numbers are used to name cultivars as in Table 1. Italic and underlined numbers represent white flesh and non-italic and non-underlined numbers represent yellow flesh.

G. Reig et al. / Scientia Horticulturae 190 (2015) 149–160

in peel and the lowest YE values were for ‘Honey Royale’ and ‘Nectapink’, while ‘Honey Kist’, ‘NG-187’, ‘Nectaearly’ and ‘Nectagala’ had the opposite behavior. In constrast, the highest flavor and AQI, and the lowest RAC in peel were recorded on ‘ASF 06-07’, ‘Big Top’, ‘Diamond Ray’ and ‘Honey Glo’, while ‘Nectarroyal’ had the opposite behavior. ‘Big Top’ is considered the reference and the most highly valued and widespread cultivar in the European Union in the last decade (Berra et al., 2011; Hilarie and Giauque, 2003; Iglesias, 2010). The results for the eight non-melting cultivars are presented in Fig. 3. The first two PCs accounted for the 75% of the explained variance. ‘Hesse’ had the highest RI and RAC in flesh, and the lowest AQI and YE, while ‘Fercluse’ had the opposite behavior. In addition, this last cultivar had the highest RAC in peel and the lowest flavor. The highest flavor was for ‘Summersun’. As expected, the behavior of flat peach cultivars differed to those of melting peach, nectarine and non-melting peach (Fig. 4); however, a similar explained variance was obtained (60%). YE in flat peaches had a medium to strong relationship with flavor, and also RAC in peel with RAC in flesh had a medium to strong relationship. ‘ASF 05-93’, ‘Donutnice’, ‘UFO 4’ and ‘Platifun’ had a high YE, high flavor, high RAC in both flesh and peel, and a low RI and AQI. Multivariate analysis has also been used to study different germplasm collections of Prunus spp. (Abidi et al., 2011; Font i Forcada et al., 2014a) and Malus × domestica (Gasi et al., 2011; Pereira-Lorenzo et al., 2003), and to study commercial peach cultivars (Reig et al., 2013a,b). However, to the best of our knowledge, no reports have jointly presented the three main characteristics of a peach cultivar (agronomic performance, fruit appearance, and internal fruit quality) together in a PCA model in order to identify the most adapted cultivars in a given area. The results obtained in the present work demonstrate that no single cultivar meets all the desirable criteria mentioned previously, namely high YE, high AQI, high RAC, strong flavor, and medium to high RI. However, some of the cultivars tested met some of these requirements, as described above. 4. Conclusions The study of the agronomic, morphological, and internal quality traits of peach cultivars grown under the climatic conditions of the Ebro Valley is valuable for the development and improvement of adaptability of these cultivars. We observed a wide phenotypic variation in 89 peach cultivars and extensive variability for most of the qualitative and quantitative traits evaluated. Indeed, the AQI developed in this study could be a valuable tool for various agents operating in the fruit value chain, like marketers and breeders. Of note, no study has simultaneously addressed agronomic, morphological and internal fruit quality traits in a wide range of commercial peach cultivars. These results highlight the difficulty to find cultivars that combine all the desired traits (high YE, high AQI, high RAC, strong flavor, and medium to high RI). This observation is possibly attributable to the fact that the cultivars included in the present study were developed for breeding programs in other countries. Given the increase in the availability of cultivars with a diversity of agronomic, morphological, and fruit quality traits, we conclude that the methodology developed herein will allow breeders and growers to select the cultivars most adapted to Mediterranean conditions while simultaneously ensuring high agronomic performance and covering market and consumer requirements. Acknowledgement G. Reig was supported by an INIA fellowship from the Ministry of Science and Innovation of the Spanish government.

159

Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.scienta.2015. 04.019

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