Prof. S.K. Mitra reported that the lychee, which originated in southern China and possibly northern Viet Nam, is now an important fruit crop of China, India, Thailand, Viet Nam, Nepal and Bangladesh. China is the largest producer of lychee in the world (1,270,000 tonnes) and about 320,000 people are involved in the lychee industry.
The varietal base of lychee in all the countries of the region is quite narrow, except in China. About 5-10 varieties are grown commercially in different countries. The productivity varies from 1 to 15 tonnes per hectare. The harvesting season is also very narrow except in Australia and Thailand. Due to lack of variation/diversity and narrow genetic base, new varieties suitable for wide climatic conditions could not be developed. An ideal variety for modern requirements is still lacking since previous criteria, based on fruit size and quality, did not take into account factors such as maturity period, regular bearing and high yield potential, wider adaptability to ecological conditions, tree characteristics, and resistance to physiological disorders.
Inadequate availability of high quality planting materials and poor field establishment of air-layered plants are some of the constraints to rapid area expansion. Recent interest in the crop should promote critical investigation of efficient methods of propagation by grafting and budding. The use of dwarf rootstocks would promote high-density plantings.
Australian horticulturists demonstrated that canopy management by pruning maintains tree size and promotes flowering and cropping. The technique should be evaluated in other countries. Nutrition management programmes for sustainable production based on leaf and soil nutrient standards are not available for most of the lychee growing countries of the region. The water requirements of the tree have been investigated and a schedule of irrigation is available for Australian lychee orchards. However, specific recommendations for other countries are not available.
Low and irregular bearing is a major problem in commercial lychee cultivation. Many aspects of the flower initiation processes and subsequent flowering behavior still remain to be studied. An alternative approach involves critical study of manipulating techniques which restrict vegetative flushing and promote vegetative dormancy and floral initiation i.e., cinturing, spiral girdling, applying growth retardants, and withholding irrigation and fertilizer application.
Lychee is subject to a wide range of pests that attack the tree, flowers and fruit. However, very few of the regular pests affect production and need to be controlled. Lychee should be harvested only when it is fully mature, and brix:acid ratio is considered as the index of maturity in most countries. Once lychees are picked, they start to dry out and become brown. Fruits should be kept in high humidity conditions and cooled to 5°C as quickly as possible. Fruits are normally shipped using refrigerated transport, which retains the red skin colour and greatly prolongs the shelf-life. China, Australia and Thailand export lychees regularly, mostly to Hong Kong, Singapore and European countries.
