Isolation of the β-tubulin gene and characterization of thiabendazole resistance in Gibberella pulicaris

Abstract

Gibberella pulicaris (anamorph: Fusarium sambucinum), is a common potato pathogen that produces trichothecene mycotoxins and reduces plant yield and tuber quality. Field isolates have been recovered from western Canada that are resistant to thiabendazole, a benzimidazole fungicide registered in many countries to control dry rot in storage. To characterize this resistance, homokaryons were derived from single ascospores that were produced in vitro from crosses of thiabendazole-resistant G. pulicaris field isolates with sensitive isolates of an opposite mating type. The β-tubulin gene was amplified from these homokaryons using degenerate oligonucleotides synthesized to conserved sequences of the β-tubulin gene derived from related fungi. An open reading frame containing three putative introns and a deduced amino acid sequence of 446 amino acids exhibited a high level of homology to the β-tubulin gene of other fungi. Although nucleotide and amino acid differences were observed in the β-tubulin gene, none were linked to the thiabendazole resistance. Linkage analysis confirmed that the isolated β-tubulin gene is single copy and was not linked to thiabendazole resistance in G. pulicaris.