Study On The Sensitivity Of Pyricularia Grisea To Isoprothiolane And Tricyclazole In Heilongjiang Province

The sensitivity to isprothiolane and tricyclazole of 65 strains of rice blast (Magnaorthe grisea, anamorph:Pyricularia grisea) from different areas of Heilongjiang Province were measured by mycelium growth rate method. The EC₅₀ of the strains tested to isoprothiolane ranged from 1.1847～6.8976μg·mL^-1, a difference of more than 5.8 times; The results showed that the sensitive base to isprothiolane was 3.7472μg·mL^-1 and resistance isolates have not been found, and all isolates measured are sensitivity ones, but there existed different degrees of sensitivity to the medicament among the strains.The results of geography region division of measured isolates showed that the more sensitive isolates to isprothiolane distributed in the local area of Mudanjiang, Tonghe County and the lacal area of Hegang, distribution of the majority of more insensitive ones is the mid-south parts of Heilongjiang Province, about along the north latitude 45.3～45.7.The EC₅₀ of the strains tested to tricyclazole ranged from 1.1847～6.8976μg·mL^-1, a difference of 4.94 times; a lowed resistance isolate was detected, appeared in the Hegang City.The more sensitive isolates to tricyclazole distributed in the east of Heilongjiang Province, centra- lized on Suibin, Fujin, Baoqing and Hulin. The isolates of local area of Hegang City were most insensitive.The sensitivity to isprothiolane of 10 strains of rice blast from different areas of Heilongjiang Province were measured by mycelium growth rate method. The EC₅₀ of the strains tested to isoproth- iolane ranged from 1.8071～4.7542μg·mL^-1, a difference of more than 2.6 times; The resulted also revealed that the sensitivity of the strains to isoprothiolane was decreased gradually among the generations in the experiment of continuously 10 generations of growth on YPDA medium with isoprothiolane (8μg·mL^-1) under fungicide pressure. The research results showed that the isolates of rice blast generate resistance mutation easily, the low resistance isolates and mid resistance isolates were obtained. The resistant degree of IPT^r was higher than the one of patent strains, and mycelia growth rates were different between IPT^r and patent strains, spore formation amount of the majority of mutagenic resistance strains and patent strains differences inconspicuousness, on determination of pathogenic ability, disease index of only strains Y-LE and Y-SJ reached significant differences, having resistance risk.This paper studyed on resistance risk to tricyclazole of 10 physiological races of rice blast in different areas of Heilongjiang Province. The strains were sensitive ones, the research results indicated that the sensitivity of the strains to tricyclazole was on descending trend through ion volume condition under reagent continuous domestication, this manifestationa was inconsistency among various physio- logical races. Meanwhile, were obtained by methods of reagent and ultraviolet mutation. The resistant degree of IPT^r was higher than the one of patent strains, but only 1/3 tested tricyclazole–resistant inducible strains were to LR isolates. Mycelia growth rates were different between IPT^r and patent strains, the mean of yielding spore formation ability of tricyclazole–resistant inducible strains indoor decreased slightly, but pathogenic ability of mutagenic resistance strains and patent strains have no significant difference.