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Abstract Detail


Population Genetics

Brown, Jennifer [1], Lawrie, Joseph [1], Rocha, Oscar [2], Moore, Richard [1].

Impacts of demographic history, population subdivision, and non-random mating on the genetic structure of natural populations of Carica papaya.

In Costa Rica, dioecious, small-fruiting papaya, Carica papaya, have been observed growing within secondary lowland forests. Within the Costa Rican landscape, agricultural abandonment has promoted the resurgence of secondary forest growth, with papaya serving as a pioneer species. The goal of this research is to address the impacts of demographic history, population subdivision, and non-random mating on the genetic diversity within these natural populations of papaya from Costa Rica. Diversity was assessed in using two datasets from five natural populations: 1) twenty microsatellites were genotyped for 184 accessions and 2) twelve loci were sequenced for single nucleotide polymorphisms (SNP) within 42 accessions. Analyses of microsatellite diversity indicate natural populations exhibit a deficiency of heterozygotes (HO=0.3-0.4, FIS=0.312). Low levels of silent site nucleotide diversity (πsil=0.00104, θsil=0.00085) were observed within the SNP loci, supporting previous reports of reduced levels of diversity within papaya. Microsatellite data indicate low to moderate pairwise FSTvalues, reflecting little genetic variation among natural populations. STRUCTURE analyses support the presence of cryptic genetic population structure. Two microsatellite-based indices were used to assess the demographic history of the natural populations. A significant value of the Garza-Williamson index (M=0.52) indicated the occurrence of a population bottleneck within the natural populations. Our estimates of the Imbalance index support a recent reduction in population size followed by population expansion for these natural papaya populations (lnß1=2.11-2.37, lnß2=2.58-2.78). The observed population bottleneck and expansion were possibly promoted by the abandonment of agricultural fields and the spread of secondary forests. These insights will provide useful information for the conservation and maintenance of genetic diversity for the cultivated plants.

Broader Impacts:


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1 - Miami University, Botany, 316 Pearson Hall, Oxford, OH, 45056, USA
2 - KENT STATE UNIVERSITY, Department Of Biological Sciences, 256 CUNNINGHAM HALL, KENT, OH, 44242, USA

Keywords:
Carica papaya
microsatellite
SNP
Population expansion
Population structure
Tropical fruit crop.

Presentation Type: Oral Paper:Papers for Topics
Session: 26
Location: Portland Room/Chase Park Plaza
Date: Tuesday, July 12th, 2011
Time: 10:45 AM
Number: 26011
Abstract ID:280


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