Selection,characterization and genetic analysis of laboratory mutants of <Emphasis Type="Italic">Botryotinia fuckeliana</Emphasis> (<Emphasis Type="Italic">Botrytis cinerea</Emphasis>) resistant to the fungicide boscalid |
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Authors: | Rita M De Miccolis Angelini Wassim Habib Caterina Rotolo Stefania Pollastro Francesco Faretra |
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Institution: | (1) Department of Plant Protection and Applied Microbiology, University of Bari, Via Amendola 165/A, 70126 Bari, Italy; |
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Abstract: | Resistance to the fungicide boscalid in laboratory mutants of Botryotinia fuckeliana (Botrytis cinerea) was investigated. The baseline sensitivity to boscalid was evaluated in terms of colony growth (EC50 = 0.3–3 μg ml−1; MIC = 10–30 μg ml−1) and conidial germination (EC50 = 0.03–0.1 μg ml−1; MIC = 1–3 μg ml−1) tests. Mutants were selected in vitro from wild-type strains of the fungus on a fungicide-amended medium containing acetate as a carbon source. Mutants showed
two different levels of resistance to boscalid, distinguishable through the conidial germination tests: low (EC50 ∼ 0.3 μg ml−1, ranging from 0.03 to 1 μg ml−1; MIC > 100 μg ml−1) and high (EC50 > 100 μg ml−1) resistance. Analysis of meiotic progeny from crosses between resistant mutants and sensitive reference strains showed that
resistant phenotypes were due to mutations in single major gene(s) inherited in a Mendelian fashion, and linked with both
the Daf1 and Mbc1 genes, responsible for resistance to dicarboximide and benzimidazole fungicides, respectively. Gene sequence analysis of
the four sub-units of the boscalid-target protein, the succinate dehydrogenase enzyme, revealed that single or double point
mutations in the highly conserved regions of the iron-sulphur protein (Ip) gene were associated with resistance. Mutations
resulted in proline to leucine or phenylalanine replacements at position 225 (P225L or P225F) in high resistant mutants, and
in a histidine to tyrosine replacement at position 272 (H272Y) in low resistant mutants. Sequences of the flavoprotein and
the two transmembrane sub-units of succinate dehydrogenase were never affected. |
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