Diversity among North American Spring Barley Cultivars Based on Coefficients of Parentage

Abstract

Maintenance of genetic diversity is an important safeguard against vulnerability to biotic and abiotic stresses. The coefficients of parentage, r, among cultivars computed from known pedigree information can be used as an index of genetic diversity. Because of the emphasis placed on developing barley (Hordeum vulgare L.) cultivars for the malting and brewing industry, it seemed likely that barley may have a narrower gene pool than other crop species where less emphasis has been placed on quality traits. Our objective was to examine the diversity among North American spring barley cultivars and the contribution of major ancestors to the two‐ and six‐rowed barley gene pools using the coefficient of parentage as an index of diversity. Coefficients of parentage were computed for all pairs of 167 spring barley cultivars. Mean r with major ancestors was computed for cultivars categorized by row type and era of release. A cluster analysis, performed on the coefficient of parentage matrix, produced 30 disjoint clusters. The five ancestors with highest mean r with cultivars contributed 45 and 62% of the germplasm to the early and recent two‐rowed cultivars and 52 and 44% of the germplasm pool in the six‐rowed cultivars for the two respective time periods. Mean r within the two‐ and six‐rowed cultivars was 0.11 and 0.10, respectively. Mean r within cultivars increased 180% in the two‐rowed and 36% in the six‐rowed cultivar groups from the early to recent cultivar groups. Cultivar groups formed by the cluster analysis produced mean within‐cluster r values ranging from 0.29 to 0.57. Principal coordinate analysis of the between cluster matrix showed that the two‐ and six‐rowed gene pools are essentially unrelated. Major six‐rowed malting cultivars grouped into two clusters and the major two‐rowed malting cultivars grouped into one cluster. These results show that malting barley cultivars are based on a limited sample of germplasm.

Population structure and linkage disequilibrium in elite barley breeding germplasm from the United States

“…The MN and N6 programs share the highest number of rare SNP markers, suggesting a close relationship between them (Table 3). This pattern of sharing is consistent with an ancestry study showing that MN and N6 share four common ancestors out of only six and seven total ancestors for the two programs, respectively (Martin, 1991). Low values of the Kullback-Leibler distance statistics among Midwest six-rowed spring subpopulations (sp2, sp6, and sp9) from STRUCTURE analysis (Table 5) and overlapping scatter plots of Midwest six-rowed spring lines (Fig.…”

Molecular marker genotypes, heterozygosity and genetic interactions explain heterosis in Arabidopsis thaliana

“…Rasmusson and Phillips (1997) argued that the genetic gap between elite gene pools and unimproved pools or germplasm collections is growing larger with each breeding cycle (Martin et al, 1991). Introgression of genetic diversity from unimproved collections is becoming more difficult.…”

Assessment of Genetic Diversity in Crop Plants - An Overview

“…The segregating generations resulting from a cross between individuals with high COP will exhibit less variability and vice versa. The value of coefficient of parentage ranges from zero, where cultivars are completely unrelated, to one, where two cultivars have all alleles in common [28]. The COP data matrix can be used to cluster genotypes and produce genealogically similar groups [29].…”