Litchi

Litchi is an important fruit tree in tropical and subtropical areas of the world. However, there is widespread confusion regarding litchi cultivar nomenclature, and detailed information of genetic relationships among litchi germplasm is unclear. As litchi is an introduced crop in India, it has limited genetic variability characterized by differences in flushing pattern, leaf, panicle, and fruit traits. This chapter reviews the literature on origin and distribution, collection and conservation, classification and identification, selection and breeding of litchi germplasm resources in India, and approaches in abroad. It is challenging to conserve litchi germplasm through seed, field maintenance, and in vitro storage because of its recalcitrant nature, owing to various biotic and abiotic factors. Of all the various strategies of ex situ conservation of litchi, cryopreservation of litchi germplasm using its embryonic axis or pollens is a promising option for conservation of germplasm. The storage of pollen at 4 °C is suitable for field pollinations in the blooming season for up to 2 months. However, storage at −86 °C maintained the high germination rates required for artificial hybridization even in the second year of storage. The classification of litchi can be possible based on morphological traits, by isozyme analysis and DNA markers. At present, most of the new litchi cultivars are selected from superior seedlings obtained after open pollination or sport; germplasm with desirable characteristics such as aborted seeds, rather big fruit, and rather late-bearing fruit has not been fully exploited. Molecular characterization revealed different cases of synonymies and homonymies in the genotypes studied in litchi. In order to achieve the goal of improving fruit quality and agronomic characteristics, it is suggested that additional studies of genetic diversity on litchi should be carried out with more powerful markers such as SSR and ISSR; marker-assisted selection (MAS) should be employed to improve litchi crossbreeding efficiency. Besides this, it is demonstrated that SRAP markers can be used for variety identification and genetic construction of litchi. Interestingly high polymorphism and low gene diversity have been exposed by molecular markers, commenting on narrow genetic background of litchi cultivars from India.