Study On Haloxyfop-R-methyl Resistance Of Digitaria Sanguinalis (L.) Scop. In Soybean Field

As a major weed species in rape field, Digitaria sanguinalis has a strong impact on yield and quality of soybean. On the basis of collecting Digitaria sanguinalis populations in soybean field, germination characteristics of Digitaria sanguinalis was studied. Then, indoor bioassay method was conducted to determine haloxyfop-R-methyl resistance of Digitaria sanguinalis, and the mechanism of haloxyfop-R-methyl resistance was studied. Finally, preliminary study on chemical control of haloxyfop-R-methyl resisitant Digitaria sanguinalis was carried, which would provide scientific basis for field control of haloxyfop-R-methyl resistant Digitaria sanguinalis. The results were as follows:The results showed that temperature, pH, light, soil humidity and depth of burial all had a certain effect on germination of Digitaria sanguinalis seeds. The optimum condition for germination of Digitaria sanguinalis seeds were as follows:temperature of 25～35℃,pH of 7.0～7.5, light period of 12h/12h, soil humidity of 20%～40%, and depth of buria between 0～1cm. Under these optimum conditions, the highest seedling emergence of Digitaria sanguinalis was observed.The resistant level of twelve Digitaria sanguinalis biotypes to haloxyfop-R-methyl were determined by seed bioassay and whole plant bioassay methods, respectively. The results showed that different bioassays may have different resistance level. In this paper, resistance level of Digitaria sanguinalis biotypes determined by seed bioassay were a little higher that that determined by whole plant bioassay method. The results of whole plant bioassay showed that IC50 value of Hubei Tianmen biotype was 49.201mg/L, and its relative resistance ratio was high level resistance of 104.23. Relative resistance ratio of other 7 biotypes from Hunan Xiangyin, Jiangxi Jiujiang, Jiangxi Pengze, Hebei Cangzhou, Hebei Handan, Henan Luyi and Henan Xinxiang were between 10～100 of medium resistance level. Relative resistance ratio of biotypes from Hunan Hanshou and Hunan Anxiang were between 3～10 of low resistance level; Relative resistance ratio of biotypes from Hunan Taoyuan was 1.89, and it is still sensitive to haloxyfop-R-methyl.Resistance mechanism of Digitaria sanguinalis to haloxyfop-R-methyl was studied. The results showed that GST activity of resisitant Digitaria sanguinalis biotype was significantly higher than sensitive biotypes after haloxyfop-R-methyl treatment. SOD and CAT activity of resisitant Digitaria sanguinalis biotype was significantly higher than sensitive biotypes. POD activity of resisitant Digitaria sanguinalis biotype had no sigficance difference with sensitive biotypes. MDA content in resistant biotype was significantly lower that sensitive biotype after haloxyfop-R-methyl treatment. The results of sequence alignment of ACCase gene showed that there was no difference between ACCase gene of resistant and sensitive Digitaria sanguinalis biotypes. It can be seen haloxyfop-R-methyl resistance of Digitaria sanguinalis may be related to factors like enhance of GST, SOD and CAT activity, while not related to mutation of target gene.Herbicides having good control effect on haloxyfop-R-methyl resistant Digitaria sanguinalis were screened. Herbicides for soil treatment such as 99% acetochlor EC,33% pendimethalin EC,72% metolachlor EC, herbicides for spraying such as 7.5% Imazethapyr. Imazaquin AS,52% Fluoroglycofen-ethyl. Clomazone EC,48% Clomazone EC,5% imazethapyr AS,7.5% Imazaquin AS,24% Fluoroglycofen-ethyl EC all had effective control effect on haloxyfop-R-methyl resistant Digitaria sanguinalis, and the stem control effect and fresh weight control of these herbicides were above 90%.