Elucidation of the factors affecting poor flowering in litchi (Litchi chinensisSonn.) and measures to overcome

Abstract

It is a major concern of litchi growers in many locations that yields are often irregular and frequently below the trees bearing capacity. Poor litchi flowering is a worldwide problem, especially in regions where the weather during the induction period is too worm. Induction of flowering in litchi requires an average minimum temperature of approximately 10-14°C for 4-12 weeks, depending on the cultivars. Variation in time of panicle emergence, panicle development, and anthesis among the cultivars in relation to seasonal progressions in temperature affect the fruit set. Experimental evidence suggest that temperature above 15°C increased vegetative growth and reduced or eliminated flowering. However, the temperature above which flowering fails is still not clear, nor is the time that the plants needs to grow at lower temperature for successful flower induction. It has also been suggested that not only is low temperature needed for induction, but also water stress throughout the autumn and winter. Six weeks autumnal water stress was reported to cause a significant increase in flowering of 'Mauritus' and 'Floridian' litchi in Israel. Gibberellins inhibits flowering in litchi and counteracts the flower-inducing influence of low temperature, while treatments such as cincturing, root pruning and application of growth retardants reverse the inhibitory effects of high temperature. It is believed that the conversion of vegetative bud to panicle in litchi is dependent on changes in content of endogenous growth substances. This paper discussed the various factors influencing the flowering in litchi and available technology to overcome.