2022 CTRE: Botrytis spp. obtained in Norwegian forest nurseries are resistant to fungicides
From Bert Cregg
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From Bert Cregg
Botrytis spp. obtained in Norwegian forest nurseries are resistant to fungicides
Authors: Katherine Ann Gredvig Nielsen, Magne Nordang Skårn, Venche Talgø, Martin Pettersson,
Inger Sundheim Fløistad, Gunn Mari Strømeng, May Bente Brurberg, Arne Stensvand
Division of Biotechnology and Plant Health, Norwegian Institute of Bioeconomy Research (NIBIO), Ås, 1431, Norway
Department of Plant Sciences (IPV), Faculty of Biosciences (BIOVIT), Norwegian University of Life Sciences (NMBU), Ås, 1432, Norway
Division of Forest and Forest Resources, Norwegian Institute of Bioeconomy Research (NIBIO), Ås, 1431, Norway
Occurred live 9:00-9:30, June 8, 2022
Abstract
Gray mold, caused by Botrytis spp., is a major challenge for forest nurseries producing Norway spruce (Picea abies) seedlings. Losses are common despite the use of fungicides for gray mold control. A total of 53 Botrytis isolates were obtained from P. abies seedlings in Norway from 2013 to 2019. Between November 2018 and June 2019, 68 Botrytis isolates were obtained from various locations indoors in three forest nurseries. Botrytis isolates were obtained from the air using open agar plates and from various surfaces in production areas using sterile cotton swabs. In addition, four Botrytis isolates were obtained from weeds in the genera Epilobium and Chenopodium growing near P. abies seedlings.
Botrytis isolates were identified to species level; 90% were B. cinerea and more than 60% of these were further characterized as Botrytis group S. Botrytis pseudocinerea was obtained from P. abies, and in a pathogenicity test it infected P. abies seedlings, causing development of necrotic tissue and conidiation. Results demonstrate that B. pseudocinerea can cause gray mold in P. abies seedlings, a Botrytis species not previously reported in this host. In addition, four isolates obtained from forest nurseries were similar to B. prunorum in regions of the g3pdh and nep2 genes used for species identification.
A mycelial growth assay was used to test for fungicide resistance, and resistance to the following fungicides was detected (percentage of resistant isolates in parentheses): boscalid (8.8%), fenhexamid (33.6%), fludioxonil (17.6%), pyraclostrobin (36.0%), pyrimethanil (13.6%), and thiophanate-methyl (50.4%). The cytb, erg27, mrr1, sdhB, and tubA genes were analyzed for the presence of known resistance-conferring mutations and those leading to G143A, F412S,∆L497, H272R, and E198A/F200Y were detected, respectively. Detection of fungicide resistance in the gray mold pathogens in forest nurseries illustrates the need for fungicide resistance management and inoculum control.