EVALUATION OF HEAT TOLERANT POTATO HYBRIDS UNDER TROPICAL CONDITIONS

Potato has long been considered a crop oftemperate climates. Bushnell (1) defined 17°Cas the optimum mean temperature fortuberization in potatoes. Night temperaturesabove 20°C severely depress both tuberinitiation and bulking, and temperatures above25°C effectively stop tuber production (6).Potato tuberization is also reported to dependlargely on the night temperature and not onthe average daily temperature (5). In lowlandtropics, including peninsular India, high dayand night temperature are the majorconsiderations resulting in loss of tuber yield(2) due to reduced partitioning of assimilatesto tubers. In India potato crop is grown mainlywhen the day temperature is below 30°C andnight temperature is below 20°C. In order todevelop heat tolerant potato varieties crosseswere made amongst known heat tolerant andlocal high yielding genotypes, and the progenywas screened by their ability to form tuberswithin one month after shifting to hightemperature (5).In southern India, the high elevation regionin Kerala occupies about 28.6% of totalgeographical area of the state and offers amplescope for raising cool season vegetable crops