多菌灵在果园白三叶青贮中的降解及其对微生物群落的影响

为了解白三叶青贮后不同浓度多菌灵农药的降解情况和果园喷施多菌灵对白三叶青贮过程中细菌多样性的影响，扩大具有农药残留的果园覆盖植物利用途径，在喷施不同浓度［2.0 （RU^-），2.5 （RU），3.0 g·L^-1 （RU⁺）］的多菌灵后进行白三叶青贮，以喷水为对照，发酵60 d。采用Miseq高通量测序技术，分别在青贮开始前、青贮第3和60天取样，对白三叶中细菌群落多样性进行研究。结果表明，青贮后多菌灵降解率达到59.6%以上，喷施量越高，降解率越高；多菌灵处理显著（P<0.05）增加了白三叶青贮发酵的乳酸、乙酸、丙酸含量，乳酸在多菌灵RU^-、RU、RU⁺浓度下分别增加了47.55%、63.24%、71.08%，乙酸分别增加了24.49%、44.90%、46.94%，丙酸分别增加了66.67%、187.50%、250.00%，有利于白三叶青贮饲料营养成分的保留；多菌灵喷施显著（P<0.05）改变了白三叶青贮菌群群落构成，增加了青贮的菌群丰度、多样性；多菌灵处理中乳球菌属、魏斯氏菌属、泛菌属、Rosenbergiella、假单胞菌属、寡养单胞菌属、肠杆菌属、芽孢杆菌属菌群丰度增加，不利于青贮发酵，但随着青贮时间的推移，寡养单胞菌属、肠杆菌属、芽孢杆菌属等菌群丰度减少。喷施多菌灵后有利于青贮发酵微生物菌群的丰度增加，对青贮发酵有害菌、多菌灵降解菌群丰度及青贮微生物多样性产生影响，青贮后多菌灵残留高于欧洲食品安全局规定的作物类动物饲料中农药最大残留量，达不到饲用标准。研究结果可为具有农药残留的白三叶青贮饲料的饲用安全性和果园覆盖植物资源的开发利用提供理论依据。

Degradation of carbendazim in orchard white clover silage and its effect on the microbial fermentative community

This research investigated the degradation of carbendazim fungicide residues in white clover （Trifolium repens） silage cut within an orchard and the effect of carbendazim residues on the diversity of the fermentative microbial community， to explore options for the use of cover plants with pesticide residues in orchards. Different carbendazim concentrations （2.0， 2.5， 3.0 g·L^-1，_{with a water spray as Control） were sprayed on white clover prior to ensiling. The silage was harvested after 60 days fermentation at room temperature. Samples were taken before ensiling， on the 3rd day and on the 60th day after ensiling to study the diversity and composition of the microbial fermentative community using Miseq high-throughput sequencing technology. The degradation rate of carbendazim during was found to be up to 59.6%， and the higher the application rate， the higher the degradation rate. Carbendazim treatment significantly increased the content of lactic acid， acetic acid， and propionic acid in white clover silage during fermentation. For days 0， 3 and 60 of ensiling， lactic acid increased by 47.55%， 63.24%， 71.08%， respectively； acetic acid increased by 24.49%， 44.90%， 46.94%， respectively， and propionic acid increased by 66.67%， 187.50%， and 250.00%， respectively. These changes enhanced the retention of nutrients in the clover silage. High-throughput sequencing results showed that spraying carbendazim significantly changed the composition of white clover silage bacterial community and increased the abundance and diversity of the silage flora. After spraying carbendazim， the abundance of Lactococcus， Weissella， Pantoea， Rosenbergiella， Pseudomonas， Stenotrophomonas， Enterobacter， and Bacillus increased and these changes not conducive to good silage fermentation. However， with the passage of time after ensiling， the abundance of Stenotrophomonas， Enterobacter， Bacillus and other flora decreased. In summary， carbendazim pesticide increased the number of microorganisms beneficial to silage fermentation， and altered the abundance of bacteria harmful to silage fermentation. Carbendazim spraying also increased the diversity of carbendazim-degrading bacteria and the silage microorganisms. The residual amounts of carbendazim in silage were higher than the maximum residue of this fungicide stipulated for feed crops by the European Food Safety Agency and hence the silage did not meet the feed standards. These results provide test data on the level of carbendazim residues remaining in herbage after ensiling following spraying and will assist in the development of safe practices for the use of orchard cover plants.}