Systemic Information for Future Perspectives in Litchi Crop Improvement

Abstract

Litchi (Litchi chinensis Sonn.) is a subtropical evergreen fruit crop of the Sapindaceae family. Over the years, significant growth in production and productivity coupled with the fast-expanding market of litchi has been recorded at both the national and international level. Most commercial cultivars in litchi have been clonally selected under Chinese or Indian conditions and have been adapted to a limited climatic condition. Disease infestation in litchi has been a long-term debate in the horticulture and agriculture sector. Keeping the damage factor as a prime concern, clonal selection as the basis of cultivar selection must rely on limited characteristics such as systemic susceptibility in terms of fruit size, quality, and period of maturity, which narrows down the diversity, focusing on only a few commercial traits. Hence, creation of variability within the litchi gene pool is of paramount importance to yield desirable characters such as precocity, dwarfness, regularity of bearing, wider adaptability, and resistance and avoidance of pests and disorders. The heterozygosity of litchi produces a wide extent of variability, which serves as the baseline for new selections through harnessing precocious genes and exploiting natural hybrid vigour and other genetic manipulations. Different strategic efforts on a breeding programme need to be undertaken on a large scale with considerations of a comprehensive survey of various genotypes and trait inheritance patterns, raising a large population of open pollinated seeds with known parentage, mutation breeding because of obvious difficulties with traditional litchi breeding and the lack of pure lines. This context provides the basic information for further improvement and genetic enhancement of the breeding programme in litchi disease resistance.