Thermal time requirement for fruit development and maturity of jujube (Zizyphus mauritiana) grown under rainfed conditions in Indian hot desert

Relationships between phenological stages in three promising cultivars of j ujube (viz., Tikadi, Seb and Gola) and ambient temperature were worked out for an established orchard in arid sub-tropical climate of NW India under r ainfed conditions. It was observed that Gola fruits mature early because th ey need relatively lesser thermal time (heat units), around 168919 degree C elsius days (degrees Cd) than others, after fruit setting. Tikadi and Cola cultivars required 335 degrees Cd and 88 degrees Cd for a mm increase in th eir fruit size, respectively. This could be one of the reasons for the fast er development rate of Gola fruits. Thermal time calculated for the fruit m aturity of different cultivars during three consecutive years 1990-93, were used for predicting the fruit maturity time during the next two seasons, 1 993-94 and 1994-95. Heat use efficiency of Cola fruits was the highest (4.5 7 kg fruit ha(-1) degrees Cd-1), followed by Tikadi and Seb cultivars.