Barnyardgrass Resistance To Quinclorac In Rice Fields

Barnyardgrass, a kind of the uppermost weed in rice fields, was used as the research subject in thispaper. The influence of different chemical reagents and mechanical damage methods on thebarnyardgrass seeds were discussed, in order to find out the effective way to break the dormancy andimprove the germination rate; the resistance of59barnyardgrass populations to quinclorac in rice fieldswere tested by single dose and whole plant bioassay，to definite the resistance level of barnyardgrass indifferent regions. And the resistance mechanism was also discussed. The results were as follows:The resistance of59barnyardgrass populations collected from the rice fields to quinclorac wastested by single dose and whole plant bioassay, the results revealed that ZJJHb population was the mostsusceptible, with a EC₅₀value of25.952g a.i./hm2and the the population from JSTX was the mostresistant, the EC₅₀value and resistance ratio were2884.079g a.i/hm2and111.13respectively; TheZJXS、ZJTY、JSWXa、JLc、AHTH、YNLCa、SCQS populations with the resistance ratio of1.14、1.48、1.97、2.58、2.89、2.91、3.00respectively, may be still at a sensitive stage or evolve low resistancenow; Other50populations also showed resistance, with the resistance ratio ranged from3.38to17.83,but the degree of resistance was different.Judging from the distribution of the resistance, the high resistant populations were mainlydistributed in Hunan Changde, western Jiangxi, the central part of Jiangsu and individual areas in Anhui,Xinjiang, Sichuan, Ningxia. The middle resistant populations were mainly distributed inJiangsu（Yangzhou、Huaian、Wuxi、Nanjing、Taizhou）, eastern Hunan（Changsha, Yuyang, Shaoyang）、Zhejiang（Hangzhou, Huzhou, Jinhua, Shaoxing, Jiaxing）, southwestern areas （Yunnan, Sichuan）.Zhejiang（ZJXS, ZHTY）, Yunnan（YNLCa）, Sichuan（SCQS）, Anhui（AHTH）, Jilin（JLc） populations maybe still at a sensitive stage or evolve low resistance now.Judging from the occurrence frequency, among the59populations, there were17high resistantpopulations,26high resistant populations, accounting for28.81%,44.07%of the total number ofsamples respectively. And7populations may be still at a sensitive stage or evolve low resistance now,which accounts for11.87%.43resistant populations totally accounts for72.88%. The above resultsshowed that the59barnyardgrass populations collected from the rice fields had evolved significantresistance to quinclorac.The population of ZJJHb and JSTX were used as the sensitive population and the resistantpopulation respectively, and the mechanism of resistance to quinclorac was discussed. The results ofdetecting the activity of β-cyanoalanine synthase indicated that the the activity of β-cyanoalaninesynthase of the JSTX population enhanced and was1.11times more than the activity of ZJJHbpopulation3days after the application of quinclorac. Whethere the differences in activity ofβ-cyanoalanine synthase in resistant and sensitive populations were the resistant mechanism, but it stillneeds further verification.