Thermal indices in relation to crop phenology and fruit yield of apple

Abstract

Field experiments were conducted on gravel sandy soil of research farm of Horticultural Research Station, Seobag in Kullu valley with ten varieties of apple for three seasons (2008-2010). In the first crop season all the varieties matured within 157-188 days, while in the second and third seasons the crop matured with 159-179 and 156-187 days, respectively. The mean GDD accumulation from bud burst to fruit set was from 382 to 419° D and to maturity 2310 to 2957° D. The varieties, Mollice and Starkrimson consumed the lowest and highest GDD for attaining physiological maturity in different seasons among all varieties. But Commercial and Tydeman consumed the lowest and highest GDD for fruit setting. The photo thermal index (PTI) in all the varieties and seasons varied from 7.2 to 16.8 and 13.2 to 18.4° D/day at flowering and reproductive stages respectively. © 2012 Government of India.