Cochliobolus sativus is the causal agent of barley spot blotch (SB), a disease responsible for serious crop losses. Triadimefon (TDM) a triazole compound is used for controlling SB worldwide. The resistance of C. sativus to TDM fungicide has been well documented, but its mechanisms are still poorly understood. ATP-binding cassette (ABC) transporters are believed to be crucial in the adaptation of fungal pathogens to a range of fungicides. In this work, TDM sensitivity of two virulent and avirulent C. sativus pathotypes was measured by the relative growth rate at four concentrations and the effective concentration for 50% inhibition (EC50) was determined. ABC1 expression was verified using quantitative reverse transcriptase (qRT-PCR). Results demonstrated that 50% mycelial growth inhibition (EC50) was achieved for both C. sativus pathotypes following TDM treatment after 96h at 0.25 µg mL-1. Moreover, qRT-PCR showed intensification of ABC1 transporter in both pathotypes 24h post TDM treatments as compared to controls. Interestingly, the ABC1 expression was greater in the virulent pathotype Pt4 as compared to the avirulent one, Pt1. Together, changes in ABC1 levels after TDM short-term treatment in both C. sativus pathotypes suggested its importance in the triazole resistance.
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