Detection of stay-green QTL in a sorghum recombinant inbred population based on cross (N13 × E36-1)

The progress in genetic improvement of post-rainy sorghum for drought tolerance using traditional plant breeding practices has been slow, and selection has not been much effective due to complex interaction between genotype and environment. Identification of genetic factors involved in stay-green through molecular breeding approaches would provide the basis for genetic improvement for drought tolerance. In this experiment stay-green QTLs were mapped and the effect of environment on stay-green expression was observed. For this a sorghum Recombinant Inbred Line (RIL) population was field evaluated for 2 years during the post-rainy season of 2011 and 2012, under two water regimes, (stress and control). A set of 200 entries, including 180 RILs, parents and checks were sown in a plot of 2 rows of 2m in RCBD design with 3 and 2 replications for stress and control treatments, respectively. Data was recorded for percent green leaf area (%GLA) with a weekly interval basis (7 counts) with starting from 50% flowering till physiological maturity. This reveals significant genotypic variances along with high heritability. A genetic linkage map based on 176 RILs with 271 markers consisting of SSRs, DArT and two qualitative traits was developed. In total 45 QTLs were identified for seven %GLA scores in two seasons and two treatments. The phenotypic variation explained by each QTL ranged from 6.00 to 14.00%. In further across environment analysis, some QTLs may be environment specific and some may consistent across environment, such stable QTLs could be utilized through genomics approaches to improve drought tolerance of post rainy sorghum varieties.