Mechanistic Responses of Contrasting Sorghum Genotypes for Resilience to Early Vegetative Stage Chilling Stress.

Terminal heat and drought stress are increasingly becoming a major bottleneck to sustain sorghum productivity, as sorghum is constantly pushed to harsher environmental conditions. Inducing greater chilling tolerance during germination, emergence and early vegetative stage can be an alternative and a more pragmatic approach compared to long and arduous route to breed for terminal heat and drought stress resilience. To identify novel donors and explore genetic diversity for early stage chilling tolerance, Sorghum Association Panel with 361 accessions were challenged to chilling (20/10^oC; day/night temperature), and optimum (30/20^oC) temperatures during germination (Experiment 1) and seedling emergence (Experiment 2), under controlled environment chambers. Using different approaches (i) Genome-Wide Association Mapping derived haplotypes with contrasting chilling response and (ii) Physiological response disaggregated through principal component analysis, two different sets of contrasting lines from the initial 361 were assembled. Both contrasting sets of accessions from (i) and (ii) are exposed to the same chilling and optimum temperature mentioned above and exposed to two different duration of exposure (15 and 30 days after emergence). Independent set of seedlings were harvested and a shoot physiological (emergence index and chlorophyll fluorescence) and rooting parameters (total root length, density and anatomical parameters) will be assessed to identify resilient donors to be included into ongoing breeding programs.