Optimization of sowing dates in Indian mustard (Brassica juncea L.) to combat yield losses caused by high temperature at reproductive stage

A field experiment was undertaken during the Rabi seasons of 2019-20 and 2021-22 at organic farm of Amity Institute of Organic Agriculture, Amity University, Noida, Uttar Pradesh, India, for the optimization of the sowing time period to reduce the effect of heat stress on Indian mustard (Brassica juncea L.) for increasing productivity. 32 Indian mustard germplasms were sown at three different time periods viz., the last week of September, the last fortnight of October, and the second week of November. Our results revealed that the mustard crop showed a substantial increase in yield supporting characters such as the number of siliqua and seeds per siliqua when sown at last week of September as compared to the second week of October, whereas the late sown crop resulted in less yield due to the heat stress faced by crop during the anthesis stage as compared to early and optimum sowing. The mean seed yield per plant showed a positive correlation with mean test weight. We established the positive effect of early sowing over optimal and late sowing in Indian mustard; further, we found a few mustard accessions were able to resist different climatic conditions. The mustard germplasm accessions IC296688, IC296703, IC296732, IC305130, IC401575, IC426385, and IC589669 were high yielding among all the accessions and can be considered as heat stress tolerant.