Sharma-Poudyal Dipak, Schlatter Daniel, Yin Chuntao, Hulbert Scot, Paulitz Timothy
Oregon Department of Agriculture, Salem, Oregon, United States of America.
United States Department of Agriculture-Agricultural Research Service, Wheat Health, Genetics and Quality Research Unit, Pullman, Washington, United States of America.
PLoS One. 2017 Sep 12;12(9):e0184611. doi: 10.1371/journal.pone.0184611. eCollection 2017.
In the dryland Pacific Northwest wheat cropping systems, no-till is becoming more prevalent as a way to reduce soil erosion and fuel inputs. Tillage can have a profound effect on microbial communities and soilborne fungal pathogens, such as Rhizoctonia. We compared the fungal communities in long-term no-till (NT) plots adjacent to conventionally tilled (CT) plots, over three years at two locations in Washington state and one location in Idaho, US. We used pyrosequencing of the fungal ITS gene and identified 422 OTUs after rarefication. Fungal richness was higher in NT compared to CT, in two of the locations. Humicola nigrescens, Cryptococcus terreus, Cadophora spp. Hydnodontaceae spp., and Exophiala spp. were more abundant in NT, while species of Glarea, Coniochaetales, Mycosphaerella tassiana, Cryptococcus bhutanensis, Chaetomium perlucidum, and Ulocladium chartarum were more abundant in CT in most locations. Other abundant groups that did not show any trends were Fusarium, Mortierella, Penicillium, Aspergillus, and Macroventuria. Plant pathogens such as Rhizoctonia (Ceratobasidiaceae) were not abundant enough to see tillage differences, but Microdochium bolleyi, a weak root pathogen, was more abundant in NT. Our results suggest that NT fungi are better adapted at utilizing intact, decaying roots as a food source and may exist as root endophytes. CT fungi can utilize mature plant residues that are turned into the soil with tillage as pioneer colonizers, and then produce large numbers of conidia. But a larger proportion of the fungal community is not affected by tillage and may be niche generalists.
在太平洋西北地区的旱地小麦种植系统中，免耕作为一种减少土壤侵蚀和燃料投入的方法正变得越来越普遍。耕作会对微生物群落和土传真菌病原体（如丝核菌）产生深远影响。我们在美国华盛顿州的两个地点和爱达荷州的一个地点，对长期免耕（NT）地块与传统耕作（CT）地块相邻区域的真菌群落进行了为期三年的比较。我们使用真菌ITS基因的焦磷酸测序技术，在标准化后鉴定出422个操作分类单元（OTU）。在其中两个地点，NT地块中的真菌丰富度高于CT地块。黑腐质霉、土生隐球菌、卡多孢属、齿裂菌科物种和外瓶霉属在NT地块中更为丰富，而在大多数地点，格孢腔菌属、座囊菌目、小麦球腔菌、不丹隐球菌、透明毛壳菌和炭疽茎点霉在CT地块中更为丰富。其他丰富的类群，如镰刀菌属、被孢霉属、青霉属、曲霉属和大隔孢伏革菌属，未表现出任何趋势。诸如丝核菌（角担菌科）等植物病原体数量不足以观察到耕作差异，但弱根病原体博莱微dochium bolleyi在NT地块中更为丰富。我们的结果表明，NT地块中的真菌更善于利用完整的、正在腐烂的根系作为食物来源，并且可能以根内生菌的形式存在。CT地块中的真菌可以利用随着耕作翻入土壤的成熟植物残体作为先锋定殖者，然后产生大量分生孢子。但更大比例的真菌群落不受耕作影响，可能是生态位通才。
