Variation in stalk rot resistance and physiological traits of sorghum genotypes in the field under high temperature

Abstract

Sorghum grown in semi-arid regions is often exposed to stresses during reproductive development, leading to decreased grain yield. In field studies using irrigation, here we (1) evaluated 45 sorghum genotypes in a randomized complete block design with three replications for 3 years for tolerance to high temperature (HT) and resistance to Fusarium stalk and charcoal rots, (2) identified traits conferring tolerance to HT and resistance to two stalk rot diseases, and (3) studied the relationship between Fusarium stalk and charcoal rots with HT. The fungi Fusarium thapsinum and Macrophomina phaseolina were injected into stalks during anthesis. Relative chlorophyll content, photosystem II quantum yield (Fv/Fm), leaf temperature, lesion length, and grain yield were measured. Year had a significant effect on plant height, chlorophyll, Fv/Fm, leaf temperature, lesion length, and seed yield. HT stress decreased chlorophyll and Fv/Fm. For inoculated plants, physiological traits were not related to lesion length or seed yield. However, the chlorophyll index had a significant, negative correlation with leaf temperature. Genotypes PI533946, IS23992, IS26749, SC35, and RTx7000 had the maximum Fv/Fm. Inoculated plants and controls differed significantly in lesion length and seed yield. Genotypes SC35, IS27912, IS19262, and PI576380 had resistance to both pathogens. Principal component analysis indicated that there was no relationship between chlorophyll, Fv/Fm, and leaf temperature with lesion length or seed yield.