Genetic Diversity of Widely Used U.S. Sorghum Hybrids 1980–2008

Sixty-three sorghum [Sorghum bicolor (L.) Moench] hybrids that are, or have been, widely used in the United States were profiled using 167 simple sequence repeat (SSR) markers. Genetic distance and cluster analysis determined that 43 (68%) of the hybrids formed seven groupings, with each group containing hybrids commercialized by a single breeding organization. Groupings were also reflective of known pedigrees. Hybrids released by different organizations were not very closely associated with one exception of two hybrids. Groupings had limited association with the decade that the hybrid was released. Numbers of alleles per locus have been constant during the past three decades with gain in new alleles being balanced by loss of other alleles. Hybrids released during the 2000s showed the least number of new alleles compared to the previous two decades. Much of the SSR allelic diversity that was introduced via the Sorghum Conversion Program that converted tropical germplasm to be day-length neutral has been deployed on U.S. farms. Continued monitoring of genetic gain and genetic diversity are important components of sustainable plant breeding strategies.