Mapping Staygreen QTLs for Post-Flowering Drought Tolerance in Postrainy Sorghum

Sorghum is the most drought-tolerant grain & straw dual-purpose cereal crop of the semi-arid tropics and subtropics, essential to human populations in the Sahel and many other semi-arid tropical regions including peninsular India. Post-flowering drought remains one of the major constraints for sorghum productions in these areas. Drought tolerance is a complex outcome of the actions of and interactions among a spectrum of genes with phenotypic effects that range from qualitative to minute, and which function in a wide range of biochemical pathways and biological processes. A F_3:8 sorghum RIL population derived from cross-(N13 × E 36-1) segregating for staygreen trait, a well characterized post-flowering drought tolerance mechanism, was field evaluated for three years during postrainy season of 2008, 2009 and 2010. A set of 240 entries including 220 individual RILs along with repeated parental genotypes and checks was evaluated with 2 rows/replication x 3-reps each for an irrigated control and stress treatment in an alpha-lattice design. Most of the traits related to drought tolerance (such as days to flowering, plant height (cm), weekly senescent/staygreen scores (from one week before flowering till maturity), grain number per panicle, test weight (g/100 seed), panicle harvest index (%), fresh stover weight/plot (g/plot), dry stover weight/plot (g/plot), grain harvest index(%) exhibited significant genotypic variance and recorded reasonably high heritability (>0.55). A linkage map with 269 loci (including SSRs and DArTs) is also generated. We will present the QTL mapping results for post-flowering drought adaptation for postrainy season sorghum.