We assessed chemical composition and variation in oil content and seed weight of 40 wild-growing almonds(Prunus L.spp.)accessions collected from different parts of Iran.There were significant differences in kernelweight and oilparameters.Accessions ranged from 0.20 to 1.5 g in kernel weight,0.2–3.0 mm in shell thickness,and 16–55%in oil content.The predominant vegetable oil components of kernels were 4.6–9.5%palmitic acid,0.4–0.8%palmitoleic acid,1.0–3.4%stearic acid, 48.8–88.4%oleic acid and 11.3–33.2%linoleic acid. Linolenic acid was detected in 15 accessions.High heritability was recorded for all studied traits and was maximum for shell thickness(98.5%)and minimum for oil content(97.1%).Maximum and minimum‘Euclidean’pair wise dissimilarities were 17.9 and 0.5,respectively. All 40 accessions were grouped into two major clusters.
Almond(Prunus dulcis Miller(D.A Webb)syn.P.amygdalus Batsch)is one of the most important nut crops and today represents the largest production of any commercial tree nut product(Woodroof 1978;Kester et al.1991). Almond species grow in subtropical Mediterranean climate,with mild,wet winters and warm,dry summers (Kester and Gradziel 1996).They originated from Central Asia and represent divergent evolution under xerophytic environments(Sorkheh et al.2009;Szikriszt et al.2011). Species of Prunus that are related to those used commercially grow wild from eastern China to mountainous areas and deserts of western China,Kurdistan,Turkistan, Afghanistan and Iran(Kester and Gradziel 1996).Iran, with a total land area of 1,648,195 km2,lies between 258 and 398 N and 448 and 638 E and is primarily subtropicalin the southern half of the country,temperate in the northern half,and mostly desert in the middle.The resultant variability in environment and climate has made possible extensive diversity in plant germplasm(Sorkheh et al. 2009).
The limited gene pool in cultivated almonds limits its cultivation to specific areas with a Mediterranean climate. The related species grow in more diverse climates therefore could have traits that enable them to survive in these climates and germplasm with these traits could be a valuable resource for breeding(Gradziel et al.2001;Sorkheh et al. 2009).The size and chemicalcomposition of the almonds is also very important.The quality of seeds is defined in particular by moisture content,lipid content,oilcomposition and oil ultraviolet absorption coefficients (Kumar et al.1994;Martin-Carralata et al.1998;Connell et al.2000).These characters are influenced by ecological conditions,location and technical and cultural practices used to extract the oil(Askin et al.2007).Among agronomical operations,irrigation may be the most important factor affecting almond kernel weight,yield and quality, and sugar composition.Irrigation has no remarkable influence on lipid contentor fatty acid composition(Soler et al.1988;Schirra and Agabbio 1989;Farhoosh and Moosavi 2006;Piscopo et al.2010;Szikriszt et al.2011).
Wild relatives of almond have notbeen subjected to any genetic improvement through domestication and are considered to possess greater natural variability compared to crop plants(Quebedeaux and Eisa 1990;Kaushik et al. 2007;Szikriszt et al.2011).For rational tree-breeding programmes,knowledge ofgenetic variability ofspecies is essential.This study was undertaken to assess wild almond germplasm collections based on multivariate analysis of seed quality traits and to quantify oil content and describe fatty acid composition of some native Iranian wild almonds and to evaluate relationships among fatty acid contents, kernel weight and shell thickness.In the search for new oilseed plants for nutritional,pharmaceutical,industrial and other uses,potentialyield of oilor fatis of paramount importance(Lawson 1995).The effectiveness of a tree improvement programme depends upon the nature and magnitude of existing genetic variability and also on the heritability of the economically important traits being pursued(Zobel and Talbert 1984;Yadav et al.2011).
This study was undertaken to assess the genetic diversity among germplasm collections of wild almond based on multivariate analysis of seed quality traits.The objectives of this work were to identify oil content and fatty acid composition of some native Iranian wild almonds and to evaluate relationships among fatty acid content,kernel weight and shell thickness.
Materials and methods
Plant materials
The wild almond species used in the study belong to the genus Prunus,subgenus Amygdalus,and include the following:P.communis(L.)Archang,P.eleagnifolia(Spach) Fritsch,P.orientalis Mill.(syn.P.argentea Lam.)in section Euamygdalus Spach;P.lycioides Spach,P.reuteri Boiss.et Bushe in section Lycioides Spach;and P.arabica (Olivier)Neikle,P.glauca(Browicz)A.E.Murray, P.scoparia Spach in section Spartioides Spach.The number of accessions sampled per site ranged from one to five, depending on habitatdiversity and availability atcollection time.The accession numbers for all samples and geographical locations of wild almond species populations collected in Iran was reported by Sorkheh et al.(2009). Wild almond trees representing in this study were marked in the native population in 2008.Field expeditions were carried out in 2009 and 2010 on the basis of recent literature(Sorkheh et al.2009),indigenous information,or conspicuous presence.Collections came from both wild and cultivated habitats concentrated in two regions in Iran. The first region(Azerbaijan and Kurdistan,36000to 38280N,44510to 45460E,mean elevation of 1,473 m a.s.l.)is characterized by relatively lush environment,mean annual rainfall of 507 mm,high biological diversity,and relatively low agriculturaldevelopment.The second region (Shahrekord and Shiraz,32170to 50510N,28580to 53410E,mean elevation of 2,030 m a.s.l.),with mean annual rainfall of 436 mm,is in a more xerophytic area with widespread agriculture.
Fruit traits and evaluation of seed quality
The fruit samples of Prunus L.spp.were collected from two regions in Iran,and were stored at-20C prior to analysis.Almond fruits from each species,five perspecies, were harvested on August 10,and nut samples were collected for two years(2009–2010).Forty nuts were randomly chosen for fruit analyses and biochemical traits.In addition,kernelweight(g)and shellthickness(mm)were recorded for each accession of wild almond species.Three replications were used for analyses of nut quality traits according to Askin et al.(2007).
We analyzed total kernel oil content and fatty acid composition.The seeds were ground and extracted with hexane by agitation in a dark place atambienttemperature for48 h following Farhoosh and Tavakoli(2008).The fatty acid profile of the oils was determined by gas–liquid chromatography and reported in relative area percentages. Fatty acids were transesterified into their corresponding fatty acid methyl esters(FAMEs)by vigorous shaking of a solution of oilin hexane(0.3 g in 7 mL)with 2 mL of 7 M methanolic potassium hydroxide at 50C for 10 min.The FAMEs were analyzed using a gas liquid chromatograph (GLC,Model-hp6890)equipped with a capillary column (30 mm 9 0.25 mm,0.25 mm film thickness),and a flame ionization detector.Temperature of both the injector and detector were 240C.The flow rate was 35 mL/min.The column temperature was 190C according to Askin et al. (2007).
Statisticalanalysis
The experimentaldesign was completely randomized with three replications.The statistical package SAS(SASInstitute 2000)was utilized for analysis of variance (ANOVA).LSD values were computed for multiple comparisons of means.Significantdifferences were recorded at p
