Effects Of Continuous Greenhouse Cucumber Cropping On Soil Bacteria And Fungus Community In Northern Henan Province

With the development of protected agriculture,serious continuous cropping obstacles has been brought by long-term intensive greenhouse production,which has greatly reduced the productivity of greenhouse production system,and become an important bottleneck restricting the sustainable development of facility agriculture.Continuous cropping obstacles are generally considered to be closely linked to the soil microbial factors,however,there are few reports on the change mechanism of soil microorganisms in greenhouse under long-term intensive planting conditions.Through discussing the variation law of soil bacteria and fungus community during continuous cropping of cucumber in greenhouse,we can provide support for elucidating the mechanism of continuous cropping obstacles,and a theoretical reference for the technology to overcome continuous cropping obstacles.In this study,continuous cultivation system of greenhouse cucumber was taken as our research target in North henan.Through collecting the different year soil samples of continuous cropping cucumber?1,5,10,15 and 20 a?,the influence on number and community structure of soil bacteria and fungi were researched with the Real-Time PCR and high-throughput sequencing technology.The main conclusions are as follows:?1?The soil physical and chemical properties were significantly changed by cucumber continuous cropping in greenhouse.The contents of soil organic matter,available phosphorus and available potassium were significantly increased associating with the extension of continuous cropping years,as did the total nitrogen and nitrate nitrogen.However,the soil dehydrogenase activity,FDA hydrolysis activity and basal respiration has showed a trend of increasing and then decreasing.?2?With the extension of continuous cucumber cropping years in greenhouse,the number of soil bacteria has not changed significantly,but the community structure changed significantly.The average relative abundance of some soil beneficial microbial communities and functional bacterial genera was varied significantly.On the level of bacteriophyta,the average relative abundance of Chloroflexi and Gemmatimonadetes was increased significantly and Nitrospirae decreased due to continuous cucumber cropping.At genus level,the relative abundance of some beneficial microorganisms,such as Bacllus,Solirubrobacter and Rubrobacter,and N cycle related microorganisms,such as Nitrospirae and Azoarcus,were decreased because of long-term continuous greenhouse cucumber cropping.Meanwhile,Some functional microorganisms,such as Agromyces,Thermomicrobium,Desulfotomaculum,Sphaerobacter and Mycobaterium were increased.The content of soil available phosphorus and organic carbon were the most important factors on driving the change of inbacterial community through redundancy analysis shows.?3?The number and community structure of soil fungi were significantly changed due to continuous cucumber cropping in the greenhouse.The number of soil fungi was increased and then decreased with the extension of continuous cropping years,and reached a peak in the soil at the 10th year of continuous cropping(about 4.49×10⁸ 18S rRNA gene copies g^-1),and the ratio of fungi to bacteria in soil also showed the similar trend.High-throughput sequencing showed that continuous cropping of cucumber significantly affected the?diversity of the fungi community,but not the?diversity of the fungi community.With the extension of continuous cropping years,the number of unique OTU in the fungus community was decreased gradually.At gate level,Ascomycota was the dominant member of the fungal community in the continuous cropping soil,but its average relative abundance was not sensitive to the continuous cropping response of cucumber.At order level,the dominant members of the fungal community contained Microascales,Pezizales,Norank_p<sub>Ascomycota and Sordariales.While Pseudallescheria,Lasiobolidium,Ochroconis,and Chaetomium were the dominant members of the fungal community at genus level.The average relative abundance of these dominant fungi was significantly affected by continuous cropping of cucumber in greenhouse,and most of them had significant linear correlation with soil physicochemical factors.The redundancy analysis indicated that the main factors driving the change of fungal community structure were the contents of organic matter nitrate nitrogen and available potassium.In general,the soil physicochemical and biochemical properties were significantly affected by long-term continuous cucumber cropping in greenhouse,and the community structure of soil bacteria and fungi were also disturbed.What's more,the occurrence of continuous cropping obstacles was largely regulated by soil microorganisms.In summary,this research shows that the results can provide to further clarify the barrier mechanism of continuous cropping of vegetables in north Henan Province.