The effect of a dominant phytophthora infestans genotype (13_A2) in Great Britain on host resistance to foliar late blight in commercial potato cultivars

A. K. Lees, J. A. Stewart, J. S. Lynott, S. F. Carnegie, H. Campbell, A. M. I. Roberts

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    As a result of recent changes in the Phytophthora infestans population in Great Britain, in particular the dominance of one genotype (13_A2) and the possible implications of this change on host resistance ratings, a coordinated programme of testing between SASA and JHI was initiated. Over 3 years of trials (2008-2010), 49 existing cultivars with published resistance ratings of 5 or greater on a 1-9 scale of increasing resistance, 42 new cultivars and a range of appropriate control cultivars were assessed using an isolate of the 13_A2 genotype of P. infestans. The mean resistance rating of 62% of the 49 existing cultivars was reduced by more than the maximum 5% LSD of 1.9. For some cultivars (e.g. Lady Balfour and Stirling), changes in resistance rating were specifically associated with the use of the 13_A2 genotype to inoculate the trials from 2008 onwards. The majority of the 42 new cultivars tested were susceptible to the 13_A2 genotype isolate, scoring 4 or less. However, cultivars with useful resistance were also identified with seven scoring 6 or 7. Published resistance ratings have been revised as a result of this study.

    Original languageEnglish
    Pages (from-to)125-134
    Number of pages10
    JournalPotato Research
    Issue number2
    Publication statusPublished - 2012

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