Effects of moderately elevated temperature stress on the timing of pollen release and its germination in tomato (Lycopersicon esculentum Mill.)

Under the increasing threat of global warming to horticultural crop production, research on moderately elevated temperature stress in relation to plant productivity becomes important and urgent. Two tomato (Lycopersicon esculentum Mill.) cultivars,'NC 8288' (a high temperature-susceptible cultivar) and 'FLA 7156' (a high temperature-tolerant cultivar) were exposed to a moderate level of high temperature stress. Reproductive development (i.e. pollen production, germination and release) in relation to anthesis, was examined under 28degrees/22degreesC and 32degrees/26degreesC day/night temperatures, respectively. High temperature stress reduced the number of pollen grains released, but not the timing of pollen release. Reductions in pollen release and germination were observed in both tolerant and susceptible cultivars; however, the magnitude of the reduction was larger in the susceptible cultivar. Furthermore, pollen grains retained in the anthers exhibited extremely poor germination. These results suggest that the pollen release mechanism and the quality of the pollen grain are closely related. Possible adverse effects of global warming on tomato productivity, and a potential breeding strategy for high temperature tolerant tomato lines are discussed.