Genomic Mapping for Drought Tolerance in Sorghum.

Sorghum is one of the most drought tolerant crops in the world and is a suitable candidate to study the drought tolerance mechanisms in crop plants. In the first study we genotype 100 SSR markers across 190 Recombinant Inbred Lines (RIL) developed from the cross Tx436/00MN7645 to identify the QTLs related to drought tolerance in sorghum. Line 00MN7645 represents an elite pollinator line with stay green, lodging resistance, and good yield potential. Stay green is a form of drought tolerance which accounts for post-flowering drought tolerance in sorghum. The testcross of RILs with ATx3042 were evaluated in a randomized complete block design with two replications, at three locations over two years for grain yield, flowering time, chlorophyll content, chlorophyll fluorescence, and leaf temperature. The second study is candidate gene association mapping for drought tolerance in sorghum. The genetic material for the experiment is sorghum diversity panel, a worldwide collection of 300 sorghum genotypes consisting of lines from sorghum conversion program and US elite breeding lines. Candidate genes are sequenced on a single nucleotide polymorphism (SNP) discovery panel consisting of 24 diverse sorghum lines, and analyzed for nucleotide diversity and linkage disequilibrium. The candidate genes were selected based on their purported functions in model plants and the QTLs discovered for drought tolerance in sorghum. The frequency of SNPs was one SNP per 100 bp on average. Haplotype and nucleotide diversities were moderately high with H_d varying from 0.879 ± 0.047 to 0.935 ± 0.052 and π varying from 0.00441 to 0.01633. This data will be used to select SNPs for association mapping.