The effect of environmental conditions in the spring and autumn on the restoration of male fertility in T-4 male sterile mutant plants which were obtained via gamma (γ)-irradiation of tomato cv. First was investigated. Vegetatively propagated sterile plants gave rise to all male sterile plants in the spring, but the same T-4 plants cultivated under uncontrolled environmental conditions in autumn yielded fertile male. Self-pollination with these fertile males resulted in 50% fruit set and 26 seeds per fruit. The selfed seeds grown in the spring and with exposure to the natural environment developed into sterile males. When these male sterile plants were selfpollinated under natural conditions in autumn, they gave rise to normal male fertile plants with an average of over 35 seeds per fruit. Short or long day treatments had no effects on the male fertility restoration. The pollen germination percentage on artificial medium was relatively higher in autumn plants compared to that grown in the spring in the T-4 mutant plants, but it remained distinctly lower than the original cv. First in the spring and autumn. Pollen tube growth following germination in the mutant plants was lacked vigor and grew slowly in the spring compared to autumn. No difference in the final pollen tube length between the mutant and normal plants was noted in autumn. We conclude from these results that pollen and seed viability in the T-4 male sterile mutant plants was restored when exposed to low temperatures in autumn.

https://doi.org/10.2503/jjshs.69.557