Mining of Resistance Gene Analogues for Anthracnose Disease in Greater Yam ( Dioscorea alata L.)

Abstract

Nucleotide-binding site- leucine-rich repeat (NBS- LRR) gene family holds the vast majority of resistancegenes identified in plants. Primers based on the conserved motifs were used to isolate NBS typesequences in tolerant and susceptible greater yam (Dioscorea alata) cultivars. Cloning and sequencingof identified NBS-type sequences called resistance gene analogues (RGAs) depicted similarity toother cloned RGA sequences available in the public database. The deduced amino acid sequences ofthe RGAs showed the presence of conserved domains, viz. P-loop, RNBS-B, RNBS-C, Kinase-2 andGLPL, categorising them with the NBS.LRR class gene family. Amino acid sequence alignment of theDioscoreaRGAs with RGAs of other plant species grouped them with the non-toll interleukin receptorsubclasses of the NBS sequences. The sequence comparison of RGAs in susceptible and tolerantvariety showed very little difference between them. This study represents the first report of isolationand characterisation of RGAs fromDioscorea alataand will act as a stepping stone for future studiesaiming at identifying candidate anthracnose resistance genes inDioscoreaspp.