Canola and mustard response to short periods of temperature and water stress at different developmental stages

Seed yield of Brassica crops in semiarid environments can be increased by minimizing the crops' exposure to high temperature and water stress that often occurs during the growing season. A growth chamber study was conducted to determine the effect of short periods of high temperature and water stress at different developmental stages on seed yield and yield components of Brassica crops. Two canola-quality Brassica juncea 'PC98-44' and 'PC98-45', a Brassica napus canola 'Quantum', and a B. juncea oriental mustard 'Cutlass' were grown under 20/18degreesC day/night temperatures with photoperiod of 16/8 h light/dark. High (35/18degreesC) and moderate (28/18degreesC) temperature stress was imposed for 10 d during bud formation, flowering, and pod development. Low (90% available water) and high (50% available water) water stress was imposed in combination with the temperature treatments. On average, the 35/18degreesC stress reduced main stem pods by 75%, seeds pod(-1) 25%, and seed weight 22% from the control. Seed yield per plant was reduced by 15% when plants were severely (35/18degreesC) stressed during bud formation, 58% when stressed during flowering, and 77% when stressed during pod development. Plants stressed at earlier growth stages exhibited recovery, whereas stress during pod development severely reduced most of the yield components. Effect of water stress on seed yield was minimal regardless of crop developmental stage. The four Brassica cultivars responded similarly to water stress. In response to temperature stress, B. juncea produced greater number of pods per plant but had a great rate of pod infertility than B. napus. Seed yield of B. juncea in semi-arid environments can be increased by improving pod fertility, whereas the seed yield of B. napus can be increased by improving pod production and retention.