Structural and functional analysis of genes with potential involvement in resistance to coffee leaf rust: a functional marker based approach

Abstract

25Physiology-based differentiation of S H genes and Hemileia vastatrix races is the principal 26 method employed for the characterization of coffee leaf rust resistance. Based on the gene-for-gene 27 theory, nine major rust resistance genes (S H 1-9) have been proposed. However, these genes have not been 28 characterized at the molecular level. Consequently, the lack of molecular data regarding rust resistance 29 genes or candidates is a major bottleneck in coffee breeding. To address this issue, we screened a BAC 30 library with resistance gene analogs (RGAs), identified RGAs, characterized and explored for any S H 31 related candidate genes. Herein, we report the identification and characterization of a gene (gene 11), 32which shares conserved sequences with other S H genes and displays a characteristic polymorphic allele 33 conferring different resistance phenotypes. Furthermore, comparative analysis of the two RGAs 34 belonging to CC-NBS-LRR revealed more intense diversifying selection in tomato and grape genomes 35 than in coffee. For the first time, the present study has unveiled novel insights into the molecular nature of 36 the S H genes, thereby opening new avenues for coffee rust resistance molecular breeding. The 37 characterized candidate RGA is of particular importance for further biological function analysis in coffee.