Regi Jacob Thomas

Coconut Breeding in India

Cocos nucifera L. is a perennial multipurpose palm grown widely in the humid tropics. It provides nutritious food and refreshing drink, edible oil and non-edible uses, fiber of commercial value, shells for fuel and industrial uses, timber and a variety of miscellaneous products for domestic and industrial uses. It is grown mainly in coastal areas and island ecosystems sustaining the livelihood of people and protecting the environment. There are conflicting theories regarding the origin and domestication of coconut. Coconut populations worldwide have been classified into two major groups: the Pacific group with five sub-groups (Southeast Asia, Melanesia, Micronesia, Polynesia and the Pacific coast of Central and South America), and the Indo-Atlantic group. The genetic resources in coconut are widely exploited through selection, hybridization for a number of desirable traits and have resulted in the development of many varieties. Breeding efforts are mostly confined to conventional approaches such as mass selection and hybridization, besides attempts to use individual palm selection for novel traits. Its perennial nature, heterozygosity, long juvenile phase and lack of technologies for mass propagation of palms with targeted traits are the challenges in breeding efforts. This chapter covers conventional breeding approaches such as mass selection and hybridization, information on varietal groups, identified genetic resources, breeding methods and techniques, current status and future strategies of coconut breeding in India.

Cloning, characterization and expression analysis of NBS-LRR-type resistance gene analogues (RGAs) in coconut

Abstract Coconut palms are highly susceptible to diseases caused by different pathogens, and replanting with resistant varieties is the best way to manage them. Obtaining a collection of resistance gene analogues (RGAs) is an effective strategy to identify genomic regions linked to disease resistance. We have successfully used a comparative genomics approach to amplify putative RGAs from the coconut root (wilt) disease resistant cultivar Chowghat Green Dwarf (CGD) by using primers designed based on conserved motifs of the NBS-LRR domain of the date palm. The amplified sequences were cloned, sequenced and characterized. The coconut RGAs had high identity to monocot NBS-LRRs. A complete structural analysis and 3-D modeling of the NBS domain of coconut RGA was also undertaken. Real-time quantitative polymerase chain reaction analysis indicated that the isolated coconut NBS-LRR class RGAs was expressed more in root (wilt) disease resistant genotypes than in susceptible ones. This study would provide a base for future efforts to map disease resistant traits in coconut.