硒砂瓜连作对土壤真菌群落结构的影响

硒砂瓜是宁夏地区重要的经济作物，其连作严重影响硒砂瓜产量和品质。目前硒砂瓜连作对土壤真菌群落结构的影响尚不清楚。本研究采用Illumina MiSeq高通量测序技术，探讨硒砂瓜连作对土壤真菌群落结构的影响。研究发现，硒砂瓜连作土壤中真菌群落多样性指数和丰富度指数随连作年限的增加先上升后下降。供试土壤样本中共检测到真菌8门、25纲、244属，其中子囊菌门（Ascomycota）、接合菌门（Zygomycota）是优势菌门，占90%以上。与对照相比，连作30年土壤中子囊菌门丰度下降32.51%，接合菌门丰度上升29.89%。供试土壤中真菌主要的优势属为被孢霉属（Mortierella）、绿僵菌属（Metarhiziun）、假霉样真菌属（Pseudallescheria）、镰刀菌属（Fusarium）和青霉属（Penicillium）。与对照相比，连作5年土壤中假霉样真菌属丰度增加45.81%，连作10年土壤中镰刀菌属丰度增加26.74%，连作15年土壤中绿僵菌属下降26.83%，连作20年土壤中青霉属增加29.68%，连作25年土壤中绿僵菌属减少18.30%，连作30年土壤中被孢霉属丰度上升29.89%。土壤理化性质与硒砂瓜连作年限间无显著相关性，而与土壤真菌群落结构存在显著的相关性。土壤全磷、碱解氮、有效磷含量是影响土壤真菌群落最主要的因素。研究结果表明，导致硒砂瓜连作障碍的主要原因不是土壤理化性质变化，而是土壤真菌群落结构的改变。研究结果可为硒砂瓜土传病害的生物防治提供参考依据。

The effect of continuous cropping of selenium melon on soil fungal community structure

Selenium-melon is an important cash crop in Ningxia, but its yield and quality decrease when continuously cropped. The decrease may be related to soil fungal community changes that take place during continuous cropping, which was determined in this study. Soil samples from continuous cropping of selenium-melon were analyzed using Illumina Miseq high-throughput sequencing. The analysis showed that, after an initial increase, the diversity and density of the fungal community in the soil of continuous cropping decreased. Eight fungal phyla, 25 classes, and 244 genera were identified in the soil samples. Ascomycota and Zygomycota were the predominant phyla, accounting for > 90% of the fungi. The abundance decreased 32.51% for Ascomycota, but increased 29.89% for Zygomycota, after 30 years of continuous cropping. The most predominant genera were Mortierella, Metarhiziun, Pseudallescheria, Fusarium, and Penicillium, and the abundance changes included a 45.81% increase for Pseudallescheria after 5 years, a 26.74% increase for Fusarium after 10 years, a 26.83% decrease for Metarhiziun after 15 years, a 29.68% increase for Penicillium after 20 years, a 18.30% decrease for Metarhiziun after 25 years, and a 29.89% increase for Mortierella after 30 years of continuous cropping. Soil physical and chemical properties were not related to years of continuous cropping, but affected the fungal community structure. Soil total phosphorus, alkaline nitrogen, and available phosphorus were the most influential factors for fungal genus changes. A significant positive correlation was observed between the abundance of Metarhizium and soil total potassium, between the abundance of Pseudomycetes and soil total phosphorus and available potassium, and between the abundance of Penicillium and soil pH, whereas a significant negative correlation was observed between the abundance of Fusarium and soil total phosphorus and alkali-hydrolyzed nitrogen. Diminished production of selenium-melon in continuous cropping was related to soil fungal community changes rather than soil physicochemical properties, demonstrating that selenium-melon soil-borne diseases might be controlled through biological means.