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Prevalence and Stability of Qualitative Qol Resistance in Populations of Venturia inaequalis in the Northeastern United States.

Authors :
Frederick, Zachary A.
Villani, Sara M.
Cooley, Daniel R.
Biggs, Alan R.
Raes, Jessica J.
Cox, Kerik D.
Source :
Plant Disease. Aug2014, Vol. 98 Issue 8, p1122-1130. 9p.
Publication Year :
2014

Abstract

Quinone-outside-inhibitor (Qol) fungicides are a safe and effective means of managing apple scab caused by Venturia inaequalis. To determine the prevalence of both quantitative (partial) and qualitative (complete) Qol resistance in V. inaequalis in the northeastern United States, we sampled single-lesion conidial isolates (n = 4,481 ) from 120 commercial and research orchards from 2004 to 2011 with a range of exposure to Qol fungicides from none to several applications a year. In all, 67% of these orchard populations of V. inaequalis were sensitive to Qol fungicides, 28% exhibited Qol practical resistance, and 5% were not sensitive Qol fungicides but had not become practically resistant. Isolates with qualitative Qol resistance, conferred by the G143A cytochrome b gene mutation, were found in 13 of the 34 Qol-resistant orchard populations. To evaluate the stability of the G143A mutation, 27 isolates were selected from different orchard populations to represent the scope of regional populations. These isolates were subcultured continuously in the presence or absence of the Qol fungicide trifloxystrobin. All isolates that initially possessed qualitative resistance maintained the resistant genotype (Gl43A) for six transfers over 6 months in both the absence and presence of trifloxystrobin. Given the observed Qol resistance in orchard populations of V. inaequalis and the stability of the G143A mutation in individual isolates, apple scab management paradigms must encompass strategies to limit selection of Qol resistance in the sensitive orchard populations remaining in the region. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
01912917
Volume :
98
Issue :
8
Database :
Academic Search Index
Journal :
Plant Disease
Publication Type :
Academic Journal
Accession number :
97300756
Full Text :
https://doi.org/10.1094/PDIS-10-13-1042-RE