BIOCHEMICAL MARKERS ASSISTED SCREENING OF PAKISTANI WHEAT (Triticum aestivum L.) CULTIVARS FOR TERMINAL HEAT STRESS TOLERANCE

Heat stress is an important abiotic constraint limiting crop productivity. An experiment was conducted to elucidate the impacts of heat induced biochemical transformations on morphological attributes of Pakistani wheat genotypes. Experiment was laid out in randomized complete block design (RCBD) with the split plot arrangement during the winter season 2014-15. Main plot treatments were comprised of H-0 (No heat imposition) and H-1 [(Heat imposition from spike emergence to grain filling initiation (Feekes Scale = 10.50 to 11.00)]. Subplots treatments were comprised of eleven wheat genotypes (Punjab-2011, AARI-2011, Galaxy-2013, Millat-2011, Aas-2011, Fareed-2006, Chakwal-50, Mairaj-2008, Pakistan-2013, NIBGE-NIAB-1 and Kohistan-97). Under heat over control, lesser decrease in chlorophyll contents and enhancement in antioxidant activities were depicted by Aas-2011, Chakwal-50, and Mairaj-2008. Higher chlorophyll degradation and diminishment in antioxidant activities under heat stress over control was observed for all other cultivars. Comparatively lower grain filling rate, higher duration, number of grains per spike and grain yield was observed for cultivars Aas-2011, Chakwal-50, Mairaj-2008 and Punjab-2011 under heat stress over control. Conclusively, based on biochemical response and morphological markers genotypes Aas-2011, Chakwal-50, and Mairaj-2008 manifested heat tolerance. Genotypes Fareed-2006 and Punjab-2011 manifested medium heat tolerance. Whereas, genotypes AARI-2011, Galaxy-2013, Millat-2011, Pakistan-2013, NIBGE-NIAB-1 and Kohistan-97 depicted susceptibility to terminal heat stress.