High temperature effect on grain growth in wheat cultivars: an evaluation of responses

Wheat (Triticum aestivum L) cvs. DL 153-2, C306, HD 2329 and WH 542 were grown under normal (27 November) and late (28 December) sown conditions. In an another experiment these wheat cultivars, except that HD 2285 replaced C306, were grown under normal sowing and at anthesis stage were transferred to control and heated open top chambers (OTCs). Under late sowing, wheat cultivars were exposed to mean maximum temperature upto 3.6ºC higher than normal sowing, whereas, under heated OTCs, mean maximum temperature was 3.2ºC higher than control OTCs, during grain growth period. In spite of more or less similar increase in temperature during grain growth period by late sowing and in OTCs experiment, the magnitude of responses were different. All the cultivars showed a decrease in yield by late sowing and decrease was greater than OTCs experiment wherein the significant decrease in yield under elevated temperature (ET) was observed only in two cultivars. The main effect of high temperature in OTCs appeared to be on grain size, whereas, in late sowing experiment, different yield components including grain growth rate were differentially affected in different cultivars. Nonetheless, the varietal pattern of susceptibility remained more or less same in late sowing and OTCs experiments. DL 153-2, C306 and HD2285 were relatively heat stress tolerant for grain growth and yield compared to HD 2329 and WH542. The present study further emphasized that late sowing of wheat by end of December can bring down the grain yield by 30–40% compared to November sowing. The late sowing of wheat being generally practiced because of prevalence of rice-wheat cropping system could, therefore, be one of the reasons for overall decline in wheat productivity. It appears that from late sowing experiment, one may not be able to analyse precisely the effect of high temperature experienced exclusively during post anthesis period. By late sowing, pre-anthesis phenological events determining potential yield components would also be affected which were then carried over to grain growth phase and influenced the grain growth and yield.