Impact of high temperature at pod development stage on yield and quality of Brassica juncea cultivars under controlled conditions

A study was conducted to assess the impact of short and long periods of high temperature in yield and quality of Indian mustard (Brassica juncea L. czery & Coss.) High temperature during reproductive phase affects the yield and quality of cool season crops to a greater extent than summer crops. Brassica juncea cultivars ‘Pusa Bold’ and ‘Pusa Agrani’ were exposed to high day temperature (35°C) at pod development stage for 5 and 10 days to assess their impact on yield parameters and seed quality. Longer exposure to stress caused drastic yield reduction in ‘Pusa Bold’ and ‘Pusa Agrani’ by 54% and 69% respectively. ‘Pusa Bold’ showed 23% increase in seed weight/pod at brief period of stress without any change in seed number whereas ‘Pusa Agrani’ was adversely affected. Significant decrease in soluble starch and increase in crude protein content were observed at longer exposure to high temperature in ‘Pusa Agrani’ that was at the expense of oil synthesis in the seeds. Fatty acid composition showed an increase in percentage of monosaturated fatty acid and decrease in polyunsaturated fatty acid under longer period of stress. At longer stress period thousand seed weight and seedling vigor index of both the cultivars were adversely affected. The differential response observed in the 2 cultivars of B. juncea under exposure to different periods of stress exhibited the adaptive mechanism in ‘Pusa Bold’ as it is a long duration cultivar and brief exposure to high temperature is compensated by maintaining net photosynthetic rate and by increased translocation to the developing seed. The shorter duration of seed development in ‘Pusa Agrani’ would accentuate the differences between the cultivars with varying rates of accumulation of seed reserves.