Differential response of pearl millet genotypes to high temperature stress at flowering

Abstract

Aim : Pearl millet is emerging as an important irrigated summer crop in India and Africa. Flowering during summer coincides with high temperature resulting in reduced grain yield. Due to limited cultivar options for summer, different types of pearl millet genotypes were evaluated to identify sources of high temperature tolerance. Methodology : Fourteen pearl millet cultivars (4 each of population and hybrids; 3 each of inbred restorers and MS lines) were evaluated under two sowing dates in such a way that the flowering was not/minimally affected by high temperature stress (non-stress - NST) and the flowering largely coincided with high temperature (≥ 42oC), impacting the seed set and grain yield (stress - ST). The data on different parameters including grain yield was recorded and different stress indices were estimated. Results :The total number of days each genotype flowered was reduced by ~2 - 3 days under high temperature stress, probably an inherent avoidance mechanism. Per cent decrease in seed set and grain yield under stress was 2.4 - 29.9 and 12.2 - 40.9, respectively. High temperature stress (≥42oC) during flowering stage resulted in reduced seed set, tip sterility and reduced panicle exertion. Increased vegetative growth (plant height) coupled with reduction in grain yield were recorded for all the genotypes under heat stress. Under temperature stress, hybrids outperformed the others in terms of seed set and grain yield. Based on heat tolerance/susceptibility indices, seed set and grain yield CZH 233, CZP 9603, CZI 2011/5 and CZMS 21A were the best performing genotypes. Interpretation : High temperature affects the assimilate production and reproductive growth, thereby significantly reduced the grain yield. The results demonstrated that flowering period is an important heat sensitive stage. Genetic variability exists for flowering stage high temperature tolerance in pearl millet which can be utilized in developing improved cultivars for summer cultivation.