Development of Fungicide Cross Resistance in Helminthosporium solani Populations from California

Plant Disease
M G Cunha, D M Rizzo

Abstract

Helminthosporium solani populations on potato from the Tulelake area in California frequently have been exposed to thiophanate-methyl but not benomyl. Assessment of three H. solani populations found that 182 of 238 isolates were resistant to both thiophanate-methyl and benomyl and 56 isolates were sensitive to both fungicides. None of the isolates exhibited a differential reaction to the two fungicides. The effective concentrations that reduced growth by 50% for resistant isolates of H. solani were approximately 400 mg/liter for thiophanate- methyl and 35 mg/liter for benomyl. Two point mutations were detected in the β-tubulin gene from H. solani isolates from California; however, only the mutation at the 455-nucleotide position (codon 198) was strongly associated with thiophanate-methyl resistance. This mutation led to a change of glutamic acid to alanine at codon 198. Independent of fungicide resistance, a mutation at the 836-site was detected in all California isolates. A polymerase chain reaction (PCR)-based restriction fragment length polymorphism (RFLP) assay was used to identify thiophanate-methyl resistance in H. solani; resistant isolates exhibited two DNA fragments of 390 and 482 bp, whereas sensitive isolates had thr...Continue Reading

References

May 11, 1992·Nucleic Acids Research·J L Cenis
Jul 11, 1995·Nucleic Acids Research·S H De BoerS Chittaranjan

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Citations

Nov 1, 2015·Plant Disease·Paul P PriceSebastian Albu
Nov 30, 2016·Frontiers in Microbiology·Nichola J Hawkins, Bart A Fraaije

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