Partial Resistance Stability of Some Common Potato Cultivars to Natural Late Blight Infection Caused by Phytophthora infestans under Egyptian Conditions

Abstract

Late blight caused by Phytophthora infestans is one of the most devastating diseases on potato worldwide. Partial resistance (PR) to the oomycete pathogen Phytophthora infestans was studied for ten potato cultivars in Beheira, Gharbia and Kafr El-Sheikh governorates in Egypt. Final disease severity (FDS%), area under disease progress curve (AUDPC) and rate of disease increase (r-value) were used as epiphytotic parameters to estimate PR during the growing seasons of 2016 and 2017. The cvs. Burren, Cara and Bellini exhibited the highest levels of PR to late blight, where they showed lowest values of FDS (%), AUDPC and r-value in both seasons of evaluation. Four measures i.e., means x, regression coefficient (b1), standard deviation (S2d) and ecovalance (wi) were used for determining the partial stability resistance of the tested potato cvs., to late blight infection. Stability parameters clearly showed that cv. Bellini was the most stable to late blight under wide range of environmental conditions. The stability analysis can help breeders to monitor the level of resistance of the tested plant material as well as to monitor the disease pressure in different environments.