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Evaluation of Genetic Diversity and Genome‐wide Linkage Disequilibrium among U.S. Wheat ( Triticum aestivum L.) Germplasm Representing Different Market Classes
Author(s) -
Chao Shiaoman,
Zhang Wenjun,
Dubcovsky Jorge,
Sorrells Mark
Publication year - 2007
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci2006.06.0434
Subject(s) - biology , germplasm , linkage disequilibrium , genetic diversity , analysis of molecular variance , population , genetics , genetic distance , genetic variation , disequilibrium , evolutionary biology , genetic structure , botany , haplotype , genotype , gene , medicine , demography , sociology , ophthalmology
Genetic diversity and genome‐wide linkage disequilibrium (LD) were investigated among 43 U.S. wheat ( Triticum aestivum L.) elite cultivars and breeding lines representing seven U.S. wheat market classes using 242 wheat genomic simple sequence repeat (SSR) markers distributed throughout the wheat genome. Genetic diversity among these lines was examined using genetic distance‐based and model‐based clustering methods, and analysis of molecular variance. Four populations were identified from the model‐based analysis, which partitioned each of the spring and winter populations into two subpopulations, corresponding largely to major geographic regions of wheat production in the United States. This suggests that the genetic diversity existing among these U.S. wheat germplasm was influenced more by regional adaptation than by market class, and that the individuals clustered in the same model‐based population likely shared related ancestral lines in their breeding history. For this germplasm collection, genome‐wide LD estimates were generally less than 1 cM for the genetically linked loci pairs. This may result from the population stratification and small sample size that reduced statistical power. Most of the LD regions observed were between loci less than 10 cM apart. However, the distribution of LD was not uniform based on linkage distance and was independent of marker density. Consequently, LD is likely to vary widely among wheat populations.