Population Structure, Genetic and Racial Diversity Analysis for Grain Mold Resistance in Selected Sorghum Accessions.

The enormous genetic diversity of grain sorghum has facilitated its flexibility to adjust to a wide range of environments to become food/feed grain of global importance. One important example is grain mold resistance where accessions evolved under humid and warm conditions tend to express high degree of resistance to the disease. This study was initiated in order to assess the extent to which the observed dynamics of resistance could be explained. One hundred and twenty-three accessions from diverse geographic origin and racial ancestry which included 111 unique grain mold resistant sources of various racial categories collected from Pawe and Asosa areas in western Ethiopia and 12 US lines of mixed racial backgrounds were investigated. The accessions were genotyped using 23 sorghum simple sequence repeat markers.  Genetic diversity and population structure was performed using PowerMarker and STRUCTURE software systems, respectively. The results were further confirmed by principal component analysis carried out using XLSTAT. The diversity analysis grouped the Pawe and Asosa collections into separate clusters with few admixtures, while all US lines were grouped in another separate cluster. Population structure analysis also identified three subpopulations in the panel which correlated well with the three geographic locations that the accessions originated from and was less correlated with racial ancestries. As reported in similar previous studies, genetic structure of grain mold resistant accessions appears to have been mainly influenced by geography than racial backgrounds. But whether all the grain mold resistant sources share common resistance alleles is the subject of future investigation.