Heat unit summation - an index for predicting fruit maturity in litchi (Litchi chinensis)

摘要

Litchi (Litchi chinensis Sonn.) is one of the export-oriented fruit crops of the country. For fetching higher price in the market, production of high quality produce is of utmost importance. Apart from orchard management, cultural practices and post-harvest treatment, proper time of harvesting plays an important role for quality production. Harvesting at the optimum age of maturity reduces different kinds of pre- and post-harvest losses, assuring availability of quality fruits. Being a non-climacteric fruit, litchi is harvested after attaining optimum maturity. Different criteria are being used for determining the stage of maturity in litchi fruits. Organoleptic evaluation by Cull and Paxton, smoothening of protuberances by Gaur and Bajpai and Galan and Menini, specific gravity by Biswas and Roy are some of the criteria for deciding the harvesting time in litchi. However, computational method using heat unit accumulation during fruit growth and development has been used as an easy and feasible criteria for determining the accurate fruit maturity. This method is being used for predicting the maturity in ber by Singh et al., date palm by Pareek and grapes by Jacob since long. However, in litchi the information pertaining to heat unit summation forfruit maturity is completely lacking. Therefore, an experiment was conducted to develop a non-destructive criterion of fruit maturity, Heat Unit Summation for litchi fruits and test its validity on the basis of fruit quality under subhumid plateau region of eastern India.