The pomegranate, Punica granatum, has been cultivated as a fruit crop since antiquity. Native to central Asia, the pomegranate and its use are deeply embedded in human history with references in many ancient cultures of its use in food and medicine (Holland et al., 2009). Pomegranate produces fruit that is valued for its juice-containing arils, health benefits, and decoration and is consumed and marketed as whole fresh fruit, extracted arils, juice, syrup (grenadine), wine, teas, seed oil, and other products. In addition, it is used as an ingredient in an array of products ranging from cosmetics to nutritional supplements. Recent consumption of pomegranates has rapidly increased attributable in part to its reported health benefits that include efficacy against a wide range of conditions, including coronary heart disease, atherosclerosis, prostate cancer, hypertension, and infectious diseases (Basu and Penugonda, 2008; Holland et al., 2009; Lansky and Newman, 2007; Seeram et al., 2006).
The pomegranate fruit is spherical, crowned with a persistent calyx, and covered with a leathery pericarp derived from sepals and adhering floral tissue. Developing from a flower with showy crenulated petals, the hypogenous ovary contains a large number of ovules. Wetzstein et al. (2011) described the morphology and anatomy of the flower types in pomegranate, which consist of both hermaphrodite and functionally male flowers. Fruit are derived from hermaphrodite flowers, which have a discoid stigma covered with copious exudate, an elongated style, and an ovary with many ovules, which on fertilization develop into the hundreds of succulent juice-containing arils that make up the edible portion of the fruit. Male flowers fail to set fruit and have reduced female parts characterized by shortened pistils containing rudimentary, degenerated ovules (Shulman et al., 1984; Wetzstein et al., 2011).
Within commercial orchards, the size of fruits produced can be quite variable, even with trees of the same genotype grown under similar cultivation practices (N. Ravid, personal communication). Although pomegranates have been cultivated since antiquity, fruit attributes, particularly those related to size, are poorly defined. With market premiums for large-sized fruits and producer-targeted traits including high total aril weight and juice content, understanding fruit attributes is essential. Recent research has addressed quantitative evaluations of pomegranate fruit characteristics, but generally, objectives have been to compare genotypes for selection and breeding programs or to evaluate growth under different climatic conditions (Barone et al., 2001; Dafny-Yalin et al., 2010; Drogoudi et al., 2005; Mars and Marrakchi, 1999; Martinez et al., 2006).
Despite the long history of pomegranate culture as a fruit crop, literature is lacking on how fruit characteristics and components relate to changes in fruit size. Pomegranate exhibits considerable phenotypic diversity in fruit size among different genotypes (Drogoudi et al., 2005; Mars and Marrakchi, 1999; Martinez et al., 2006). However, the literature lacks evaluations of within-genotype fruit attributes and how fruits change in relation to size. A number of fundamental questions related to pomegranate fruit development remain unanswered. Unclear is how fruit composition changes with fruit size. What characteristics are associated with larger fruit? Do fruit components such as the proportion of aril to pericarp and membrane content stay constant or do they change with varying fruit size? Does juice content change with fruit size? What is more important to fruit size: increasing aril numbers per fruit or promoting more extensive aril enlargement?
Production strategies addressing these alternative circumstances would be quite different. Understanding the fundamental aspects of fruit development that determine size would indicate how and when size could be affected and specify which components can be environmentally manipulated versus which are fixed and under genetic control (Webb et al., 1974). Additionally, such knowledge would be useful to breeding programs that require awareness of fruit qualities in the selection of traits for improvement (Leon et al., 2004).
The objectives of this study are to evaluate fruit characteristics in pomegranate and to identify which attributes are related to size. Fruit attributes, including fruit volume and weight, aril weight and number, pericarp weight, seed weight, and juice/pulp content, were evaluated in a collection of ‘Wonderful’ pomegranate fruits of variable sizes. Correlations between fruit characteristics were determined. In addition, factor analysis was used to establish a fruit index that can be used to select and rate fruit.
BaroneE.CarusoT.MarrraF.P.SottileF.2001Preliminary observations on some Sicilian pomegranate (Punica granatum L.) varietiesJ. Amer. Pomol. Soc.5547
BlascoJ.CuberoS.Gomez-SanchisJ.MiraP.MoltoE.2009Development of a machine for the automatic sorting of pomegranate (Punica granatum) arils based on computer visionJ. Food Eng.902734
Borochov-NeoriH.JudeinsteinS.TriplerE.HarariM.GreenbergA.ShomerI.HollandD.2009Seasonal and cultivar variations in antioxidant and sensory quality of pomegranate (Punica granatum L.) fruitJ. Food Compost. Anal.22189195
Dafny-YalinM.GlazerI.Bar-IlanI.KeremZ.HollandD.AmirR.2010Color, sugars and organic acid composition in aril juices and peel homogenates prepared from different pomegranate accessionsJ. Agr. Food Chem.5843424352
DerinK.EtiS.2001Determination of pollen quality, quantity and effect of cross pollination on the fruit set and quality in the pomegranateTurk. J. Agr. For.25169173
HaradaT.KurahashiW.YanaiM.WakasaY.SatohT.2005Involvement of cell proliferation and cell enlargement in increasing the fruit size of Malus speciesSci. Hort.105447456
HiscockS.J.AllenA.M.2008Diverse cell signaling pathways regulate pollen-stigma interactions: The search for consensusNew Phytol.179286317
JohnsonK.L.MalladaA.NeSmithD.S.2011Differences in cell number facilitate fruit size variation in rabbiteye blueberry genotypesJ. Amer. Soc. Hort. Sci.1361015
JosanJ.S.JawandaJ.S.UppalD.K.1979Studies on the floral biology of pomegranate. II. Anthesis, dehiscence, pollen studies and receptivity of stigmaPunjab Hort. J.196670
KembleJ.M.GardnerR.G.1992Inheritance of shortened fruit maturation in the cherry tomato Cornell 871213-1 and its relation to fruit size and other components of earlinessJ. Amer. Soc. Hort. Sci.117646650
LanskyE.P.NewmanR.A.2007Punica granatum (pomegranate) and its potential for prevention and treatment of inflammation and cancerJ. Ethnopharmacol.109177206
MartinezJ.J.MelgarejoP.HernandezF.SalazarD.M.MartinezR.2006Seed characterization of five new pomegranate varietiesSci. Hort.110241246
McGarryR.OzgaJ.A.ReineckeD.M.2001Differences in fruit development among large- and small-fruited cultivars of Saskatoon (Amelanchier alnifolia)J. Amer. Soc. Hort. Sci.126381385
OlmsteadJ.W.IezzoniA.F.WhitingM.D.2007Genotypic differences in sweet cherry fruit size are primarily a function of cell numberJ. Amer. Soc. Hort. Sci.132697703
SchwartzE.TzulkerR.GlazerI.Bar-Ya'akovI.WiesmanZ.TriplerE.Bar-IlanI.FrommH.Borochov-NeoriH.HollandD.AmirR.2009Environmental conditions affect the color, taste, and antioxidant capacity of 11 pomegranate accessions’ fruitsJ. Agr. Food Chem.5791979209
ScorzaR.MayL.G.PurnellB.UpchurchB.1991Differences in number and area of mesocarp cells between small- and large-fruited peach cultivarsJ. Amer. Soc. Hort. Sci.116861864
WetzsteinH.Y.RavidN.WilkinsE.MartinelliA.P.2011A morphological and histological characterization of bisexual and male flower types in pomegranateJ. Amer. Soc. Hort. Sci.1368392