Terminal heat stress in Indian mustard (Brassica juncea L.): Variation in dry matter accumulation, stem reserve mobilization, carbohydrates translocation and their correlation with seed yield

Abstract

The rapeseed mustard is one of the most important sources of edible oil in India and contributes 28.6% in total oilseed production. The mustard growing areas in India are experiencing the vast diversity in the agro climatic conditions. Here, we studied forty-nine advanced breeding lines of Brassica juncea L. for two consecutive years (2016-18) to examine the variations in the remobilization of assimilates from flowering to maturity stage and their contribution to seed filling under stressed environment. Further, we investigated the impact of high temperature on dry matter accumulation and partitioning from source to sink in Brassica germplasm. The synchronization between the seed filling stage and the onset of heat spell is critical event that determines the overall yield. Imbalances caused due to miss-matching of above events created hindrance in source-sink translocation, thus resulted in yield losses. Amount of remobilized dry matter, remobilization efficiency and remobilization percentage increased significantly, while the dry matter accumulation, total carbohydrates content and seed yield per plant declined in the late sown genotypes during both crop seasons. Reduced accumulation of photo assimilates under stress and higher sink demand resulted in more number of shriveled seeds leading to yield depression. The higher remobilization efficiency in late sown genotypes was strongly associated with dry matter at flowering that consequently tended to affect the final seed weight. This study will provide insights for better understanding of source-sink relationships in Indian mustard under heat stress and the differential remobilization efficiencies in the advanced breeding lines.