LAUSR

Abstract Pythium species are aggressive soil-borne necrotrophic oomycetes causing soft-rot disease of ginger. Disease severity indices determined following infection with P. myriotylum Drechsler in ginger cultivar, Zingiber officinale cv. Varada and a wild congener, Z. zerumbet at varying zoospore concentrations (104–1012 spores/ml) revealed high disease severity (100%) in ginger cultivar whereas Z. zerumbet displayed resistance. Absence of positive correlation between Z. zerumbet resistance and polyphenolic content indicates role of polyketides and zerumbone in preventing pathogen ingress, as reported earlier. Towards elucidating this, Z. zerumbet specific polyketide synthase (PKS) and terpene synthase (TPS) gene sequences designated ZzTPS and ZzPKS respectively were characterised. Phylogenetic analysis clustered ZzTPS with TPS-b sub-family and ZzPKS with non-chalcone forming PKS. ZzTPS and ZzPKS showed biphasic expression with first at 6 hours post infection (hpi) and then at 8 hpi, indicative of rapid induction followed by reinforcement to sustain resistance mechanisms in the wild taxon.