EXPLOITATION OF RESISTANCE GENE ANALOGS ENCODING NBS-LRR DOMAINS IN WIDE HYBRIDIZATION OF COTTON

Abstract

Resistance gene analogs (RGAs) are one of the rich families of R genes that share conserved motifs and encode NBS-LRR domains. Based on this property numerous RGAs were isolated from Gossypium arboreum based on reported sequences from G. hirsutum L. in the database and subsequently cloned for nucleotide sequencing analysis. The isolated RGAs from G. arboreum showed nucleotide and amino acid homology to the reported RGAs from G. barbadense and G. hirsutum but some of them were found to be unique in phylogenetic tree and they were considered as novel RGAs. There are two possibilities of their use either to as a probe for detection and isolation of full length R genes from crop plants or to use them as markers. So, the isolated unique RGAs were used as DNA markers in F₁ generation and back crosses of G. arboreum × G. anomalum, and F₁ population of G. arboreum × G. capitis-viridis. The series of assays proved that G. arboreum is free of diseases and an important source that could be used for the development of disease resistant cotton plants. Due to this property G. arboreum is being used in inter-specific hybridization. The isolated RGA as a marker confirmed the inter-specific F₁ generation and back crosses. The process of selection from inter-specific populations can be accelerated by the use of RGA markers and also could be used as an important tool to recover desirable plants containing resistance from G. arboreum.