Assessment of the genetic diversity of Indian coconut accessions and their relationship to other cultivars, using microsatellite markers

摘要

Coconut cultivation in the Indian subcontinent over many centuries has given rise to diverse cultivar types, identified based on discernible morphological traits, geographical locations and farmers' choice. The Indian coconut germplasm base has also been enriched through introductions from other major coconut growing regions of the world. This study assessed the genetic diversity in a range of coconut accessions, and their relationship to other major coconut cultivars, using microsatellite markers. Microsatellite assay was used for 23 Indian accessions (15 Tails and 6 Dwarfs) and for 21 exotic accessions (18 Tails and 6 Dwarfs). A total of 48 alleles were detected in the Indian accessions by using 8 microsatellite primers (average 6 alleles per locus). More alleles were detected in the Indian accessions than in the exotics, indicating the presence of a wide allelic spectrum in the Indian accessions. Mean gene diversity ranged from 0.00 for 'Chowghat Green Dwarf to 0.59 for 'Lakshadweep Ordinary Tall', with an overall mean of 0.32. The within-population variation was slightly higher (53%) than the between-population variation (47%), suggesting recent local adaptation and subsequent divergence among Indian cultivars. An UPGMA dendrogram separated the Indian accessions into two groups, one clustering with South-east Asian cultivars, which are introgressed types, and another clustering with African and Sri Lankan cultivars. The results are discussed in terms of diversity of Indian coconut accessionsand relationships to other major coconut cultivars.