Significance of ploidy on par with genotypic specificity in host resistance for Phytophthora in Black pepper (Piper nigrum L.)

Abstract

We estimated Disease Severity Indices (DSI) of 22 genotypes of Black pepper by subjecting them to screening against Phytophthora capsici for assessing the influence of ploidy as well as genotype in host resistance. The DSI of the genotypes showed significant variation and established the existence of genotypic specificity in host resistance in Black pepper. ‘PAJ’, a haploid genotype of the crop, exhibited the highest resistance to the pathogen, as evident by its lowest DSI (33.33 %), and rated it as ‘moderately resistant’. Its diploid progenitor ‘PMM’ and all the other diploid genotypes were rated as ‘susceptible’, since their DSI were > 40 %. ‘PAJ’ is genetically a product of haplodisation of ‘PMM’, and it showed significantly higher resistance than ‘PMM’ for the pathogen. Hence, it is inferred that ploidy has remarkable influence in Black pepper – Phytophthorapathosystem. This study is insightful on the possible genomic interventions for augmenting the inherent degree of resistance exhibited by the genotypes of the crop for the pathogen. Therefore, outcome of this study is a breakthrough, which can transform the present-day haphazard, less efficient approach in resistance breeding in Black pepper for Phytophthora foot rot to one which is systematic and efficient.