Resistance Development to Qol Inhibitors in Populations of Mycosphaerella graminicola in the UK

摘要

Strains of Mycosphaerella graminicola resistant to Qol inhibitors were isolated in the UK for the first time at Rothamsted during the summer of 2002. Sequence analysis of the cytochrome b gene revealed that all resistant isolates carried a mutation resulting in the replacement of glycine by an alanine residue at codon 143 (G143A). High-throughput bioassays and allele-specific real-time PCR tests using G143A as marker were developed to monitor the current status of resistance to Qol inhibitors in UK field populations. Test results showed a widespread distribution of G143A in 2003, with frequencies ranging from 12 to 87 %. The R-allele (A143) frequency increased significantly after fungicide applications. For 14 commercial plots tested the average R-allele frequency increased from 41 % at the start of the season to 88 % at the end of the season after fungicide applications. Retrospective PCR testing revealed that G143A was already present in field populations during the 2000/01 growing season, albeit at a very low frequency (< 3 %).