Influence of genetic background and plant age on expression of the potato late blight resistance gene Rpi‐phu1 during incompatible interactions with Phytophthora infestans

Abstract

The goal of this study was to determine the expression profile of a late blight resistance gene, Rpi‐phu1, after challenge with an incompatible Phytophthora infestans isolate. Relative expression levels were measured by quantitative real‐time PCR, before as well as 1, 3 and 5 days after contact with the pathogen. Plants tested included diploid and tetraploid breeding lines with the gene in different genetic backgrounds and plants of a chosen breeding line at different developmental stages. All tested potato breeding lines with the Rpi‐phu1 gene were highly resistant to P. infestans and so was the line tested at different developmental stages. No significant changes were detected in Rpi‐phu1 transcript level after pathogen challenge in any of the tested tetraploid potato lines. However, Rpi‐phu1 transcription in diploid lines was enhanced by contact with P. infestans. Basal expression of the Rpi‐phu1 gene was significantly lower in the youngest, 3‐week‐old plants than in 6‐week‐old plants. Nevertheless, 1 day after inoculation with the pathogen, transcript levels in these plants were slightly greater than in 6‐week‐old plants, indicating that plant age can influence transcription of the Rpi‐phu1 gene, but that this does not affect late blight resistance.