A Quantative Real-Time PCR of Phytophthora infestans in different Indian potato cultivars

Reliable and sensitive quantification of Phytophthorainfestansin potato plant is of crucial importance in managing the multiple syndromes caused by this pathogen. A Real-Time polymerase chain reaction (PCR) assay was developed for the determination of P.infestans in host tissues. DNA levels of a highly virulent isolate were measured in different potato cultivars with varying degrees of resistance. Using SYBR Green and specific primers for P.infestans the minimal amount of pathogen DNA quantified was 0.0005ng/μl. Pathogen DNA was recorded at 24 hours postinoculation. Thereafter, the increase was rapid in susceptible cultivars and slower in resistant ones. The amount of pathogen DNA quantified in each potato cultivars correlated with susceptibility to late blight. Likewise, there was a relationship between the virulence of the pathogen and the degree of colonization. Differences also were found in pathogen amount among host tissues, with maximal pathogen biomass occurring in susceptible one. The real-time PCR technique developed in this study was sensitive and robust enough to assess both pathogen development and resistance to Late blight in different potato genotypes.