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Title: Genetic diversity in peach [Prunus persica (L.) Batsch] at the University of Florida: past present and future

item CHAVEZ, DARIO - University Of Georgia
item Beckman, Thomas
item WERNER, DENNIS - North Carolina State University
item CHAPARRO, JOSE - University Of Florida

Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2014
Publication Date: 7/25/2014
Citation: Chavez, D.J., Beckman, T.G., Werner, D.J., Chaparro, J.X. 2014. Genetic diversity in peach [Prunus persica (L.) Batsch] at the University of Florida: past present and future. Journal of Nematology. doi: 10.1007/s11295-014-0769-2.

Interpretive Summary: Genetic diversity is necessary for breeding programs to progress. The results of this study demonstrate that the University of Florida (UF) stone fruit breeding program has a very high level of diversity in its germplasm pool, higher than that reported in other studies of stone fruit germplasm diversity both worldwide and Occidental. This diversity is no doubt due to the large number of sources that have been tapped in its long history. The change in emphasis from melting to non-melting type cultivar development has resulted in a clear split in this germplasm.

Technical Abstract: The University of Florida (UF) stone fruit breeding and genetics program was created in 1952 to develop early ripening stone fruit cultivars with high quality, adaptation to summer rainfall, low chilling requirements, and the ability to withstand high disease pressure. Diverse germplasm sources were used to introduce desirable traits in UF breeding pool. The main objective of this research was to determine the genetic diversity and population structure of the breeding germplasm, and to search for loci under selection. A total of 195 peach genotypes were used: UF cultivars and advanced selections (n=168), cultivars and selections from the UF-UGA-USDA joint breeding effort (n=13), landrace cultivars (n=4), high-chilling cultivars released by NCSU (n=5), and related Prunus (n=5) species. A total of 36 SSR markers distributed across the peach genome amplified 423 alleles. An average of 18 genotypes were detected per marker: A (number of observed alleles) of 11.43, Ae (effective number of alleles) of 2.58, Ho (observed heterozygosity) of 0.4, He (expected heterozygosity) of 0.52, F (Wright’s fixation index) of 0.25, and PIC (polymorphism information content) of 0.48. UPGMA cluster analysis based on Nei’s genetic distance represented best the known pedigree information for the germplasm pools. Two major groups were observed across the germplasm corresponding to melting and non-melting flesh cultivars/selections. Population structure results supported these two major groups. Several loci closely located to genome regions where different phenotypic traits have been previously mapped were detected to be under selection.