A radical decrease in tomato yield was recorded during the summer season in India due to high temperature. In the present

investigation, twenty three tomato genotypes were screened under field condition during two consecutive seasons of springsummer

(February to May) and autumn-winter (October to February). Early flowering was observed in summer than winter

season. Pollen viability decreased greatly during summer season. Maximum viability of the pollen grains was observed in

EC-538156 (94.33 %), PS-1 (90.00 %) and Kashi Amrit (90.00 %) and the minimum pollen grains were recorded in EC-

362941 (72.00 %) during winter season. Whereas, increment of pollen viability were noted during summer in EC-538156

(94.67%), Hisar Lalit (Sel-18) (93.33%) and 15-SB (82.67%). Fruit set percent at high temperature is stringently reliant on

proper gametogenesis (pollen and ovule development) and fertilization which is markedly decrease at high temperature,

Hisar Lalit showed less reduction (15.98%) in fruit set (%) during summer than the other genotypes. In summer season Hisar

Lalit showed highest yield plant-1 1.39 kg and exhibited higher degree of heat tolerance whereas, in winter season Pant T-3,

EC-605696 and Hisar Lalit (Sel-18) performed better in terms of yield.

Key Words: Autumn-winter, Polar diameter, Spring-summer season, Tomato