Isolation and sequence analysis of putative CnSHELL gene region provides insights on phylogeny and origin of coconut tall cultivars.

Abstract

Cocos nucifera (coconut) is an economically important crop in the Philippines. Coconut is the only species in the genus Cocos of the family Arecaceae and is widely cultivated for its extensive use in agriculture and industry. The SHELL gene has already been characterized in oil palm which is responsible for its coconut-like shell and various fruit forms. However, this gene has not yet been isolated and characterized in coconut. In this study, the CnSHELL gene region was successfully amplified across 22 coconut cultivars originating from different regions and amplicon size ranges at about 450-550 bp. Based on BLAST analysis, this gene is homologous with Elaeis guineesis shell-specific gene. The isolated gene can also be mapped on the whole genome sequences of coconut deposited in NCBI. Sequence analysis of the CnSHELL gene revealed low level of genetic diversity (Hd = 0.039394, = 0.00131) which indicates that the amplified region is highly conserved. Nevertheless, phylogenetic analysis using the CnSHELL gene region showed two groups of coconut, which is consistent with previous reports on separate domestication origins of coconut. Indeed, this is the first report of SHELL gene region isolated from 22 Cocos nucifera tall cultivars.