Benzimidazole resistance offusarium species recovered from potatoes with dry rot from storages located in the Columbia basin of oregon and Washington

Abstract

Fusarium species cause dry rot or seedpiece decay of potato tubers in storage and in the field. When potato storages were sampled in the Columbia Basin of Oregon and Washington,F. sambucinum, F. oxysporum, andF. solani were the predominantFusarium species recovered from potato tubers with dry rot. OtherFusarium species recovered includedF. avenaceum, F. culmorum, F. equiseti, F. proliferatum, andF. sporotrichioides. The majority ofF. sambucinum isolates tested were resistant to thiabendazole at 5, 10, and 25 mg liter-1 in amended potato dextrose agar (PDA), whereas resistance was less frequent inF. oxysporum andF. solani isolates. When isolates ofF. sambucinum, F. solani, andF. oxysporum were grown on PDA with no thiabendazole, the average colony diameter of isolates with resistance to thiabendazole was greater than the average colony diameter of isolates sensitive to thiabendazole for each respective species. When isolates ofF. sambucinum were placed on tuber slices, lesions were apparent by four days after inoculation, and lesion diameters were generally greater than those associated withF. solani orF. oxysporum. At eight days after inoculation onto tuber slices, the average lesion diameter ofF. sambucinum, F. solani, orF. oxysporum isolates with resistance to thiabendazole was greater than the average lesion diameter of isolates sensitive to thiabendazole for each respective species. Thiabendazole-resistance was also detected inF. avenaceum, F. culmorum, F. equiseti, andF. sporotrichioides.