Conservation of plant genetic resources is important in addressing modern agricultural challenges. Population growth, food security, and climate change have resulted in the need to preserve the existing natural variation (Food and Agriculture Organization of the United Nations, 2010). Genetic diversity studies are an important aspect of conservation as they provide a record of the current variation which is the backbone of any breeding project. The Caribbean Islands are considered a zone of secondary diversification of crops leading to adaptation (Ocampo Perez et al., 2006a); therefore, its genetic diversity has always been an area of interest (Boza et al., 2013; Montero-Rojas et al., 2011, 2013; Muller et al., 2009; Rodriguez-Bonilla et al., 2014; Wendel et al., 1992).
Papaya is a tropical fruit crop belonging to the Caricaceae family. It is thought to be native to Central America and is cultivated in most of the world’s tropical areas (Arumuganathan and Earle, 1991; Food and Agriculture Organization of the United Nations, 2013; OCampo, 2007; Teixeira da Silva et al., 2007). The commercial success of papaya is not only reliant on its beneficial nutritional properties but also on the commercial uses of papain, a proteolytic enzyme found in its latex (de Oliveira and Vitória, 2011). Papaya global production in 2013 was 12,420,485 t, of which 6.02% were produced in the Caribbean (Food and Agriculture Organization of the United Nations, 2013). With a production of 8,852 t in 2013, Puerto Rico is the third largest papaya producer in the Caribbean (Food and Agriculture Organization of the United Nations, 2013).
The genetic diversity of papaya has been studied both morphologically and at a molecular level (Aikpokpodion, 2012; Alonso et al., 2009; Asudi et al., 2013; Brown et al., 2012; Matos et al., 2013; Ocampo Perez et al., 2006a; Sengupta et al., 2013; Sudha et al., 2013). Morphologically, papaya has been shown to possess great diversity (Ocampo Perez et al., 2006a). Nevertheless, at a molecular level, it has been shown that commercial papaya offers a narrow genetic basis (Matos et al., 2013).
In the recent past, SSR markers have become an effective method for assessment of genetic diversity because of their high reproducibility, codominant inheritance, and genome-wide distribution (Idrees and Irshad, 2014; Wang et al., 2009). In papaya, several SSR marker libraries have been developed and its uses have led to success in assessing genetic diversity and molecular-assisted selection for breeding purposes (de Oliveira et al., 2010; Ocampo et al., 2004; Ocampo Perez et al., 2006a; Vidal et al., 2014). But, studies on papaya in the Caribbean and surrounding countries using SSR markers are limited and none have included papaya from Puerto Rico. Ocampo Perez (2007) studied 72 accessions from 13 locations in the Caribbean using 15 SSR markers and recorded a total of 99 alleles with the samples clustering according to their geographic region. Similarly, Brown et al. (2012) found heterozygosity deficiencies in natural populations of papaya in Costa Rica after studying 164 accessions from Costa Rica and 20 known cultivars from the USDA germplasm collection using 20 SSR markers. In our study, using 23 SSR markers, we assessed the genetic diversity within 139 farmer-held papaya accessions from different municipalities in Puerto Rico. For comparison purposes, 13 other accessions from USDA germplasm and 10 commercial varieties were also evaluated.
AikpokpodionP.O.2012Assessment of genetic diversity in horticultural and morphological traits among papaya (Carica papaya) accessions in NigeriaFruits67173187
AlonsoM.AlorB.GarcíaO.MorenoQ.TeyerS.FelipeL.2009Caracterización de accesiones de papaya (Carica papaya L.) a través de marcadores AFLP en Cuba Characterising Cuban papaya accessions (Carica papaya L.) by AFLP markersRev. Colomb. Biotecnologia23139
AsudiG.OmbwaraF.K.RimberiaF.K.NyendeA.B.AtekaE.M.WamochoL.S.2013Evaluating diversity among Kenyan papaya germplasm using simple sequence repeat markersAfr. J. Food Agr. Nutr. Dev.1373077324
BozaE.J.IrishB.M.MeerowA.W.TondoC.L.RodríguezO.A.Ventura-LópezM.GómezJ.A.MooreJ.M.ZhangD.MotamayorJ.C.SchnellR.J.2013Genetic diversity, conservation, and utilization of Theobroma cacao L.: Genetic resources in the Dominican RepublicGenet. Resources Crop Evol.60605620
BrownJ.E.BaumanJ.M.LawrieJ.F.RochaO.J.MooreR.C.2012The structure of morphological and genetic diversity in natural populations of Carica papaya (Caricaceae) in Costa RicaBiotropica44179188
Carro-FigueroaV.2002Agricultural decline and food import dependency in Puerto Rico: A historical perspective on the outcomes of postwar farm and food policiesCaribb. Stud.3077107
de OliveiraE.J.AmorimV.B.O.MatosE.L.S.CostaJ.L.daSilva CastellenM.PáduaJ.G.DantasJ.L.L.2010Polymorphism of microsatellite markers in papaya (Carica papaya L.)Plant Mol. Biol. Rpt.28519530
de OliveiraJ.G.VitóriaA.P.2011Papaya: Nutritional and pharmacological characterization, and quality loss due to physiological disordersFood Res. Intl.4413061313
DoyleJ.1991DNA protocols for plants. In: G.M. Hewitt A.W.B. Johnston and J.P.W. Young (eds.). Molecular techniques in taxonomy. NATO ASI Series (Series H: Cell Biology). Vol. 57. Springer Berlin Heidelberg
EarlD.A.VonHoldtB.2012STRUCTURE HARVESTER: A website and program for visualizing STRUCTURE output and implementing the Evanno methodConserv. Genet. Resources4359361
EvannoG.RegnautS.GoudetJ.2005Detecting the number of clusters of individuals using the software STRUCTURE: A simulation studyMol. Ecol.1426112620
Food and Agriculture Organization of the United Nations2010The Second Report on The State of the World’s Plant Genetic Resources for Food and Agriculture. pp. 1–16
Food and Agriculture Organization of the United Nations2013FAOSTAT database. 12 Dec. 2017. <http://faostat.fao.org/>
JakobssonM.RosenbergN.A.2007CLUMPP: A cluster matching and permutation program for dealing with label switching and multimodality in analysis of population structureBioinformatics2318011806
Junta de Planificación2016Puerto Rico external trade data. 12 Dec. 2017. <http://www.jp.gobierno.pr/>
MatosE.L.S.OliveiraE.J.JesusO.N.DantasJ.L.L.2013Microsatellite markers of genetic diversity and population structure of Carica papayaAnn. Appl. Biol.163298310
Montero-RojasM.CorreaA.M.SiritungaD.2011Molecular differentiation and diversity of cassava (Manihot esculenta) taken from 162 locations across Puerto Rico and assessed with microsatellite markers. Annals of Botany Plants https://doi.org/10.1093/aobpla/plr010.
Montero-RojasM.OrtizM.BeaverJ.SiritungaD.2013Genetic, morphological and cyanogen content evaluation of a new collection of caribbean Lima bean (Phaseolus lunatus L.) landracesGenet. Resources Crop Evol.6022412252
MortonJ.1987Papaya p. 336–346. In: J. Morton (ed.). Fruits of warm climates. Echo Point Books & Media Brattleboro VT
MullerF.VocciaM.BâA.BouvetJ.M.2009Genetic diversity and gene flow in a Caribbean tree Pterocarpus officinalis Jacq.: A study based on chloroplast and nuclear microsatellitesGenetica135185198
NiggemannM.JetzkowitzJ.BrunzelS.WichmannM.C.BialozytR.2009Distribution patterns of plants explained by human movement behaviorEcol. Modell.22013391346
OcampoJ.A.DambierD.OllitraultP.Coppens d’EeckenbruggeG.BrottierP.RisterucciA.2004Development of microsatellite markers in papaya: Isolation, characterization and cross amplification in mountain papayasProc. Interam. Soc. For Trop. Hort.489093
Ocampo PerezJ.2007Papaya genetic diversity assessed with microsatellite markers in germplasm from the Caribbean regionActa Hort.74093102
Ocampo PerezJ.DambierD.OllitraultP.Coppens d’EeckenbruggeG.BrottierP.FroelicherY.RisterucciA.2006aMicrosatellite markers in Carica papaya L.: Isolation, characterization and transferability to vasconcellea speciesMol. Ecol. Notes6212217
Ocampo PerezJ.D’EeckenbruggeG.C.BruyereS.BellaireL.OllitraultP.2006bOrganization of morphological and genetic diversity of Caribbean and Venezuelan papaya germplasmFruits612537
PeakallR.SmouseP.E.2012GenALEx 6.5: Genetic analysis in Excel. Population genetic software for teaching and research-an updateBioinformatics2825372539
Rodriguez-BonillaL.CuevasH.E.Montero-RojasM.Bird-PicoF.Luciano-RosarioD.SiritungaD.2014Assessment of Genetic Diversity of Sweet Potato in Puerto RicoPLOS One912E116184
SenguptaS.DasB.PrasadM.AcharyyaP.GhoseT.K.2013A comparative survey of genetic diversity among a set of Caricaceae accessions using microsatellite markersSpringerplus2345355
SudhaR.SinghD.R.SankaranM.SinghS.DamodaranV.SimachalamP.2013Genetic diversity analysis of papaya (Carica papaya L.) genotypes in Andaman Islands using morphological and molecular markersAfr. J. Agr. Res.851875192
Teixeira da SilvaJ.A.RashidZ.TanD.DhariniN.GeraA.TeixeiraM.TennantP.F.2007Papaya (Carica papaya L.) biology and biotechnology p. 47–73. Tree and forestry science and biotechnology. Global Science Books London
United States Coast Guard2016Alien migrant interdiction statistics. 13 Dec. 2017. <https://www.uscg.mil/hq/cg5/cg531/AMIO/amio.asp >
VidalN.M.GrazziotinA.L.RamosH.C.PereiraM.G.VenancioT.M.2014Development of a gene-centered SSR Atlas as a resource for Papaya (Carica papaya) marker-assisted selection and population genetic studiesPLOS One9e112654
WangM.L.BarkleyN.A.JenkinsT.M.2009Microsatellite markers in plants and insects. Part I : Applications of biotechnologyGenes. Genomes Genomics35467
Zambrana-EchevarríaC.de Jesús-KimL.Márquez-KarryR.JenkinsD.SiritungaD.2016Diversity of Papaya ringspot virus isolates in Puerto RicoHortScience51362369