Characterisation of Pathogenesis-Related Genes and Resistance Gene Candidates in Banana (Musa acuminata) and Their Expression during Host-Pathogen Interaction

Amplified chitinase gene sequence shared 99% homology with musa acuminata class iii acidic chitinase and beta-1,3-glucanase gene sequence was 100% homologous to musa x paradisiaca beta-1,3-glucanase. three nucleotide-binding sites and the leucine-rich repeat (nbs-lrr) type of putative rgcs and one serine/threonine kinase gene were characterised at the amino acid level. kinase-2 (lvlddvw) and kinase-3 (gsriiittrd) motifs in the nucleotide-binding domain were highly conserved in rgc2 and rgc3 and these genes belong to the non-tir-nbs class rgcs. rgc1 was also clustered into non-tir-nbs class rgcs; however,many residue substitutions were present in the kinase-2 and kinase-3 motifs. the sub-domain ix (lteksdvysfgvvl) of serine/threonine protein kinase was highly conserved in rgc5 and it shared highest homology with pth-2 from muskmelon. rt-pcr analysis revealed the differential expression of pr and rgc genes exhibited by different banana genotypes over sampling time. chitinase was expressed during banana- focr4 interaction in all three banana genotypes. however,its expression was high and constant in rastali mutiara during banana-focr4 interaction and resulted in very low disease severity in focr4 inoculated plants (2%) compared to rastali wild-type (16%) and jari buaya (8%) at six weeks after inoculation. this suggests that chitinase may play an important role in disease resistance against focr4. besides,our study also shows that rastali mutiara can be a potential source of disease-resistant genes for molecular breeding of banana. © universiti putra malaysia press.