Resistance gene analogues in mango against mango malformation

Abstract

Mango malformation is one of the most important diseases limiting its cultivation. However, disease resistance is known in some mango cultivars and is a desirable trait that can be utilized for developing mango varieties resistant to malformation. Resistance genes cloned from different plant species have revealed several similarities in DNA sequence and structural motifs. This provides the possibility of isolating resistance genes by polymerase chain reaction (PCR) with degenerate oligonucleotide primers designed from highly conserved regions of the nucleotide binding site (NBS). In the present study, we used eight combinations of oligonucleotide primers designed on the basis of P-loop and hydrophobic domains of conserved NBS-leucine rich repeat (LRR) protein sequences for amplifying resistance gene analogues (RGAs) in eight mango cultivars and hybrids showing a variable degree of resistance to mango malformation disease. A single band of about 500 bp in all mango cultivars was obtained from the s2+as2 primer combination. RGAs isolated from mango showed 73% similarity with RGAs in databases. It confirms that RGAs were actually isolated from mango. The obtained sequence can be used for isolating full length R-genes.