Partial fertility restoration as affected by night temperature in a season-dependent male-sterile mutant tomato, Lycopersicon esculentum Mill.

This study was conducted to investigate the influence of night temperature on the restoration of fertility in a season-dependent male-sterile tomato mutant (T-4). Plants were grown in greenhouses, in which minimum and maximum temperatures were set at 10°C and 28°C by heating and ventilation, respectively. Flowers were hand-pollinated and the fruit-set, seed-set, and number of seeds were examined. The rate of fruit-set was high and did not differ much from October to February; almost all fruits formed in October had self-fertile seeds, but 80% of the fruits from November to February were parthenocarpic. The rate of fruit-set dropped from 70% in March to below 10% in May. During this period, most of the fruits were seeded, though fruit-set was low. The number of seeds per seeded fruit varied with the season, being as high as 50 seeds in October, 1-2 seeds per fruit between November and March, and 1-20 seeds per fruit between April and June. A low night temperature of 12°C did not affect fruit-set but resulted in a better seed-set than a high night temperature of 18°C in the greenhouse. Further, pollination of the plants in phytochambers also resulted in a better fruit- and seed-set at 12°C than 24°C. In all cases, the influence of low temperature was more pronounced in autumn than in spring. Fruit-set was 70% at 12°C and 46% at 24°C. Of these fruits, 50% at 12°C and 10% at 24°C were seeded. It was inferred that partial fertility restoration in T-4 can be achieved by manipulation of night temperatures. The female organ was shown to be normal, functional, and compatible with wild-type pollen. From these results, the potential of the male-sterile T-4 mutant for use in a two line hybrid-seed production system was apparent. JSHS