Dr. Ranjeet Ranjan KumarNANDINI G AT-112312024-10-012024-10-012023https://krishikosh.egranth.ac.in/handle/1/5810215305Drought stress (DS) and heat stress (HS) play negative roles in wheat growth and are the two most important factors limiting grain yield. In the present study, we have studied the effect of drought stress and heat stress on C306 (Heat tolerant), HI1500 (Drought tolerant), HD3226 (Drought susceptible), and HD3271 (Heat susceptible) on carbon metabolism, tolerance and grain quality parameters. Putative DREB 30, mtHSP and cpHSP were identified by data mining and cloned from C306 genotype with amplicon size of 858 bp, 1058 kb and 985bp respectively. BLASTn search analysis of the putative DREB 30, mtHSP and cpHSP showed the highest similarity with Aegilops tauschii and Triticum aestivum. Real-time quantitative expression analysis of the DREB 30 and cpHSP genes revealed a maximum of 6 and 21 fold increases in expression in leaves under combined stress treatment during the grain filling stage, respectively. Our study found that combined stress has severe effects on the relative water content (RWC) and photosynthetic parameters compared to individual stress. The maximum reduction in photosynthetic rate (7.0 μmol CO2/m²/sec), stomatal conductance (0.31μmolH2O/m²/sec) and transpiration rate (0.8 µmol H2O/m- ²/s-1 ) was observed in HD3271 and disintegration of chlorophyll pigments was higher in wheat cv. HD3226 (43%) under combined stress. Grain weight per spike was reduced by 30 % in C306 and 47.3% in HD 3271 under combined drought and heat stress treatment. The activity of different antioxidant enzymes such as SOD (10.7 U/mg), GPx (27.38 U/mg), and catalase (32.48 U/mg) were increased significantly in C306 under combined drought and heat stress treatment. Combined stress also resulted in higher accumulation of Proline (40.56%) and TAC (30%) with compare to control. Combined stress showed higher reduction in starch (49.70%), amylose (12.28%), amylopectin (37.41%), AGPase (1.08 U/mg) and Soluble starch synthase (1.66 U/mg) activity in HD3226. Among genotypes HD3226 was severely affected, C306 was least affected by combined stress. Overall results, suggest that combined effect of drought and heat stress has more detrimental effects than the individual stressEnglishThesis