Population of Benomyl Resistant Rice “Bakanae” Fungus in Paddy Fields

Abstract

Sensitivity to Benomyl of Bakanae pathogen, Gibberella fujikuroi, on diseased rice plants was surveyed in Iwate Prefecture from 1980 to 1987. A highly resistant isolate was discovered first in 1980 and gradually increased as well as moderately resistant isolates for the next 8 years. In 1985, both of the sensitive and resistant isolates coexisted on the same diseased sheath blade of rice plant, but in 1987 most of the isolates were highly resistant with minimum inhibitory concentration of equal to or more than 1, 000μg/ml. Such rapid development of resistance to benomyl in G. fujikuroi may be caused by successive application of this chemical as seed disinfectant.