Effects Of Fungicides On Symbiont Of Achnatherum Inebrians-Epichlo? Endophytes

In this study,the potential geographic distribution of Drunken horse grass(Achnatherum inebrians,DHG)was predicted using a maximum entropy model,and the effects of fungicides on the infection rate,alkaloid content,seedling growth,nutritional quality and soil bacterial community of DHG were investigated through4-year greenhouse and field trials.The study was conducted to provide a theoretical basis for the research on the harmless use of DHG and its ecological functions.The main results of the study are as follows.1.The BCC-CSM2-MR model simulation indicates that the suitable habitats of Achnatherum inebrians would increase under climate change scenarios.Results show that precipitation of the coldest quarter and mean air temperature of the coldest quarter are the dominant climatic factors influencing the geographic distribution of Achnatherum inebrians.Under current climate,the suitable habitats are mainly located at Xinjiang,Gansu and Qinghai.The future distribution of Achnatherum inebrians will increase under climate change scenarios.The average elevation of suitable habitats would be increased,and the center of distribution would move to the higher altitudes in mountainous areas of Qinghai-Xizang Plateau.2.Through greenhouse and field tests,we screened the number of sprays,physical treatments,fungicides and fungicide combination that had the best effect on the reduction of the infection rate and alkaloid content of DHG.The best effect of fungicide spraying 2 times in a row on reducing infection rate in DHG;compared with burning and spraying fungicide after mowing,the best effect on reducing infection rate in DHG was achieved by spraying fungicide directly without physical treatment.Three consecutive years of fungicide single spraying trials revealed that tetramycin was the most effective,with 26.67% and 125.16 mg/kg of infection rate and ergonovine content in DHG,respectively,which were 73.33% and 63.75% lower compared to the control.Two consecutive years of fungicide combination trials found that the combination of benzopyrazole and tetramycin was the most effective,with19.30% and 110.42 mg/kg of DHG infection rate and ergonovine content,respectively,which were 80.70% and 68.02% lower compared to the control.Two-year fungicide combination(benzoylprocyclazole and tetramycin)is more effective than tetramycin three-year single spray effect.3.There was no significant effect of benzoyl procyclazole and tetramycin on plant height,tillering and fresh weight of greenhouse DHG seedlings.The nitrogen-free leachate content and relative forage value of DHG increased significantly(P<0.05)compared with the control after three years of continuous spraying of benzoyl procyclazole and tetramycin alone and two years of continuous spraying of their combination.4.The effects of benzoyl procyclazole and tetramycin and their combination on the soil bacterial microbial community of DHG habitat were small,and there were significant effects on the composition of the soil fungal community,but the effects on the fungal community diversity were small.The relative abundance of soil bacterial microbial species did not differ significantly,soil bacterial Beta diversity had no effect,soil bacterial microbial Alpha diversity gradually narrowed the gap with the control,and the effect of fungicides on soil bacterial species composition gradually decreased under the conditions of single spraying of benzoyl procyclazole and tetramycin;significantly(P<0.05)changed the soil fungal community composition,while the two fungicides had significantly different effects on soil fungal community composition,and neither had a significant effect on the Alpha diversity of soil fungal microorganisms.Under compound conditions,with the extension of sampling time,soil bacterial microbial endemic OTUs increased,the relative abundance of soil bacterial microbial species did not differ significantly,increasing the Alpha diversity of soil bacteria and decreasing the Beta diversity of bacterial communities;significant(P<0.05)effects on soil fungal community composition,with the extension of sampling time did not affect the Alpha of soil fungal microbial diversity of soil fungal microorganisms,and fungal Beta diversity first significantly decreased(P<0.05)and then significantly increased(P<0.05).5.The fungicide combination(benzoyl procyclazole and tetramycin)can effectively act on different grassland types of DHG.This compound treatment significantly reduced(P<0.05)the infection rate and ergonovine content of Yongchang,Shandan and Xiahe DHG,among which the infection rate and ergonovine content of Xiahe DHG decreased most significantly,by 58.65% and 41.68%,respectively,compared with the control.There were no differences in nitrogen-free leachate and relative forage value in Xiahe compared with the control;relative forage value in Shandan was significantly(P<0.05)higher than the control,and there was no difference in nitrogen-free leachate;nitrogen-free leachate in Yongchang was significantly(P<0.05)lower than the control,and there was no difference in relative forage value.The negative effect of this compound treatment on soil bacterial microbial abundance and diversity diminished with time,and there were regional differences between Xiahe and Yongchang;there was a significant(P<0.05)effect on soil fungal community composition in both Xiahe and Yongchang,but the effect on fungal community diversity was smaller with longer sampling time.