PIRA-PCR for Detection of Fusarium fujikuroi Genotypes with Carbendazim-Resistance Alleles

Abstract

Carbendazim, a methyl benzimidazole carbamate (MBC)-group fungicide, has been used to control rice bakanae disease, caused by Fusarium fujikuroi (teleomorph: Gibberella fujikuroi), for decades in China. Previous research revealed that point mutations (E198V, GAG to GTG at codon 198, and F200Y, TTC to TAC at codon 200) of the β2-tubulin gene conferred resistance of F. fujikuroi to MBC. In this study, primer-introduced restriction analysis polymerase chain reaction (PIRA-PCR) was developed to determine genotypes with resistance of F. fujikuroi to MBC. A PCR template of each strain was created by an outer primer pair. Fragments with 177 bp (for mutation at codon 235) and 146 bp (for E198V) were amplified by nested PCR, with two inner primer pairs designed and synthesized according to the nucleotide sequence of β2-tubulin for further enzyme digestion validation, respectively. AccII and PmaCI restriction enzyme recognition sites were introduced artificially by inner primers to differentiate MBC-sensitive and -resistant strains, respectively. The sensitivity of each strain to MBC was indirectly determined by analyzing electrophoresis patterns of the resulting amplified fragments after simultaneous digestion by both AccII and PmaCI. PIRA-PCR produced the same result as conventional methods in 6% of the time. PIRA-PCR is a sensitive and effective method for genotyping resistance alleles of F. fujikuroi strains to MBC.