Sulfonylurea-resistant weeds in paddy rice fields of Japan

Resistance to sulfonylureas developed in nine annual weeds and one perennial weed found in rice cultivation areas of northern and central Japan. Some resistant populations demonstrate high sulfonylurea resistance. Fifty percent lethal doses (LD50) of some resistant biotypes were approximately 100 to 1000 times higher than those of susceptible biotypes. A rapid diagnostic method was applied to the resistant weeds, and herbicide treatment with thifensulfuron-methyl {methyl 3-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)=amino]carbonyl]amino]su lfonyl]-2- thiophenecarboxylate } under adequate illumination yielded clear results. A crossing test suggested that dominant nucleic gene(s) control the inheritance behavior of the sulfonylurea resistance. Genetic variations and gene mutation were investigated in the resistant weeds. A control method was confirmed for sulfonylurea resistance weeds in paddy fields in Japan.