Author(s):

Asha Kumari and A Hemantaranjan

Abstract: High temperature is major environmental factor that limits productivity of cereal crops all over the world. Wheat (Triticum aestivum L.), one of the main staple cereal crop, is highly sensitive to heat stress. Two screened wheat genotypes, C-306 (heat tolerant) and HUW-468 (heat susceptible), were selected to evaluate the effect of 24-epibrassinolide @1µM along with its combinations through pre-seed soaking, foliar spray and both combinations together at pre-flowering and post -flowering stage. The heat stress shock was imposed by late sowing in the field. 24-epibrassinolide treatments significantly enhanced chlorophyll, MSI, NRA, APX, and SOD in both C-306 and HUW-468 genotypes under heat stress. Among all the treatments, EBR @1µM seed treatment + 1µM foliar spray revealed higher chlorophyll (37.56 and 42.00 mg g^-1 FW) at pre-flowering stage whereas (42.43 and 44.13 mg g^-1 FW) at post-flowering stage, MSI (38.13% and 38.56%) at pre-flowering stage whereas (40.67% and 41.00%) at post-flowering stage, NRA(0.760 and0.666 µ Mol NO₂ h^-1 g^-1 FW) at pre-flowering stage whereas (0.750 and0.640 µ Mol NO₂ h^-1 g^-1 FW) at post-flowering stage, APX(49.03 and 51.50 Unitsmg^-1proteinmin^-1) at pre-flowering stage whereas(51..67and52.90 Units mg^-1 protein min^-1) at post-flowering stage, SOD (2.600 and 3.477 Units mg^-1 protein min^-1) at pre-flowering stage whereas(2.767 and 3.550 Units mg^-1 protein min^-1) at post-flowering stage in both susceptible and tolerant genotype, respectively, compared to control. 24-epibrassinolide treatments, as evident, minimized the heat stress damage in tolerant genotype as compared to susceptible genotype by enhancing chlorophyll, MSI, NRA and antioxidant enzymes activity (APX and SOD).

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