Physiological and Biochemical Effects of Heat Shock Stress and Determination of Molecular Markers Related to Heat Tolerance in Maize Hybrids

Heat shock stress causes alteration in the physiological and molecular characteristics in plants due to the generation of reactive oxygen species which cause reduction in plant growth. In this study, four maize hybrids (Sc122, TWC 321, TWC 324 and TWC 352) were grown under normal temperature (25x202f;degrees C) and after 12 days, a set of the four hybrids with three replicates was exposed to heat shock (45x202f;degrees C) for 2x202f;h. The results showed on the one hand that heat shock stress caused an increment in phytohormones (auxin, gibberellic acid and zeatin) except abscisic acid in two maize hybrids (Sc122 and TWC 321). On the other hand, all the parameters mentioned above were decreased significantly in the other maize hybrids (TWC 324 and TWC 352). In addition, osmolytes (proline and glycine betaine), polyamines (spermidine, putrescine, and spermine) and total soluble sugars were significantly increased in all maize hybrids but the most pronounced increases were recorded in the two maize hybrids Sc122 and TWC 321. These results confirm a previous study that the maize hybrids Sc122 and TWC 321 are considered as tolerant genotypes and the other two hybrids (TWC 324 and TWC 352) as sensitive genotypes. Differential gene expression under normal and heat shock conditions were adopted to search for some heat responsive genes in Egyptian maize hybrids. Three out of the five designed primers produced fragments. Alignment analysis revealed resemblance of the resulted fragments and some heat responsive genes in different species.