PARAQUAT RESISTANCE IN JAPAN

Abstract

In Japan, from the beginning of the 1980s the control of Erigeron philadelphicus L. has become increasingly difficult in mulberry fields near to Tokyo. In 1982, paraquat resistant E. canadensis L. was also found in vineyards in Osaka Prefecture, and in 1987 Conyza sumatrensis Retz. and Youngia japonica (L.)DC. were found in mulberry fields. A survey in Spring 1989 showed that paraquat resistant E. canadensis was most widely distributed especially in the west half of Japan from Kanto area to Kyushu. The second paraquat resistant weed, E. philadelphicus, was found in the Kanto area and Yamanashi Prefecture. The other two species, C. sumatrensis and Y. japonica were restricted to only three prefectures in the Kanto area. Resistance has been observed in four biotypes of Compositae weeds in perennial crop farms where paraquat had been applied 2 or 3 times annually during the preceding 15 to 20 years. In E. philadelphicus and E. canadensis, the ecological and physiological fitness of the resistant biotype is lower than that of the normal types as is the case for atrazine-resistant weeds. Crossing experiments with E. philadelphicus provided evidence that a single dominant gene was responsible for paraquat resistance. Although there are reports showing that differences in the paraquat movement in weeds may be associated with paraquat resistance, we showed that the resistance to paraquat was observed at the protoplast level, by the measurements of chlorophyll bleaching, Mehler reaction and superoxide detoxification system.