The Resistance To Tribenuron-methyl In Galium Aparine L. In Winter Wheat Fields Of Northern China

Galium aparine L. is a troublesome weed in winter wheat fields in northern China. In order to evaluate the resistance of Galium aparine L. to tribenuron-methyl, 14 wheat field biotypes were collected from winter wheat fields of 14 counties or cities in Shandong, Shanxi, Henan, Hebei, Jiangsu, Shaanxi, and Anhui Provinces, and 14 susceptible biotypes were correspondingly collected from the nearby non-farming lands never applied herbicides.A qualitative method in Petri dish for detection of herbicide resistance to tribenuron-methyl in Galium aparine L. was established, single concentration discrimination method. This method together with Petri dish resistance level bioassay, the quick detection of herbicide resistance to tribenuron-methyl of large population of Galium aparine L. can be achieved, which has important practical significance to herbicide resistance monitoring and to scientific and rational herbicide use.28 biotypes in all were detected for the profile of Galium aparine L. herbicide resistance to tribenuron-methyl, by the single concentration discrimination method greenhouse pot tests and Petri dish resistance level bioassay.Based on the work done above, the biotype with relative higher herbicide resistance was selected, and the enzymology mechanism of resistance was discussed by the research on the target enzyme acetolactate synthase (ALS), important plant metabolic enzyme glutathione-s-transferase (GSTs), and the protective enzyme (SOD,POD).For the sake of the rational herbicide resistance control strategy and scientific and rational herbicide use, the cross-resistance of Galium aparine L. to bensulfuron-methyl, fluroxypyr meptyl, isoproturon, thifensulfuon methyl, and 2,4-D 1-butyl ester.The results are as follows:ⅠThe single concentration discrimination method 1. Significant difference of germination rate between resistance and susceptible biotypes was obtained under the discrimination concentration, 85μg a.i./mL.2. Under the discrimination concentration, the germination rate of the susceptible biotypes was from 0 to 27.6%; except for the wheat field biotypes from the collecting sites of Tai'an, Shandong Province, Shijiazhuang, Hebei Province, Taiyuan, Shanxi Province, and Zhouzhi, Shaanxi Province, with the germination rate being lower than 20%, the germination rates of all the other wheat field biotypes were above 20%, and significant difference between resistance and susceptible biotypes was obtained. The wheat field biotypes from Tai'an, Shandong province, Shijiazhuang, Hebei Province, Taiyuan, Shanxi Province, and Zhouzhi, Shaanxi Province were primarily estimated as susceptible biotypes, all the other wheat field biotypes had developed different degree resistance to tribenuron-methyl.ⅡThe resistance level detection of Galium aparine L. to tribenuron-methyl1. The results of greenhouse pot tests showed that except for the wheat field biotypes from the collecting sites of Shijiazhuang, Hebei Province, Taiyuan, Shanxi Province, Zhouzhi, Shaanxi Province, and Tai'an, Shandong Province, with a resistance factor 1.2, 1.1, 1.1, and 0.9 respectively, all the other wheat field biotypes evolved resistance to tribenuron-methyl, with a resistance factor ranging from 1.6 to 4.3. The resistance was relatively higher in Henan Province. The resistance was relatively lower in Anhui, and Jiangsu Provinces than in Henan Province. The resistance factor of Shandong Province was about 2. The resistance in Shaanxi Province was low, and the resistance factors of Baoji and Huaxian were 1.7, 1.6 respectively. The wheat field biotypes collected from Hebei and Shanxi Provinces were still susceptible.2. The results of Petri dish showed that except for the wheat field biotypes from the collecting sites of Shijiazhuang, Hebei Province, Taiyuan, Shanxi Province, Zhouzhi, Shaanxi Province, and Tai'an, Shandong Province, with the resistance factors all being 1.0, the other wheat field biotypes had developed different degree resistance to tribenuron-methyl, with the resistance factors lower than 2, from 1.5 to 1.9, except for the biotypes from the collecting sites of Zhoukou and Xuchang of Henan Province and Zaozhuang of Shandong Province, with the resistance factors above 2, being 2.2, 2.2 and2.1 respectively. The wheat field biotypes collected from Hebei and Shanxi Provinces were still susceptible. The results of the quick-test in Petri dish are in accordance with those of greenhouse pot tests on the whole.ⅢThe resistance mechanism of Galium aparine L. to tribenuron-methyl1. In vitro, there was no significant difference between the sensitivity of ALS from the R and S biotypes to tribenuron-methyl. The resistance to tribenuron-methyl in the resistant biotype is not due to the sensitivity of ALS. The study on Michaelis-Menten equation of ALS in vitro showed that no significant difference exists between the Km of ALS from the R and S biotypes, and no significant difference exists between the Vmax. Kinetics of enzyme-catalyzed reactions showed no difference between ALS from the R and S biotypes.2. In vivo, the activity of ALS from S biotype was inhibited, while that of R biotype was high. This may be one of the reasons why Galium aparine L. to tribenuron-methyl. The high activity of ALS from R biotype after application may be owing to the overexpression of ALS gene.3. The GSTs activity of R biotype was higher than that of S biotype on the whole. The correlation between GSTs activity and herbicide resistance indicated that the difference of metabolizable ability of GSTs to tribenuron-methyl is the other important reason of herbicide resistance to tribenuron-methyl.4. No significant difference existed between POD activity of both R and S biotypes, and no significant difference existed either. Oxidative stress is not related to the mode of action of tribenuron-methyl.ⅣThe cross-resistance of Galium aparine L. resistant to tribenuron-methylThe detection of cross-resistance showed that the R biotype was resistant to 2,4-D 1-butyl ester, with a resistance factor 2.5, but still was susceptible to bensulfuron-methyl, fluroxypyr meptyl, isoproturon, and thifensulfuon methyl.