| China is the largest potato producer in the world,while the average potato yield of China is lower than that of the world.The continuous cropping of potato in China,especially common in south China,has caused serious continuous cropping obstacles,increased diseases and insect pests,and decreased yield and quality.The continuous cropping obstacle and its control have been well studied.Most of these studies are carried out in one season crop area,such as Gansu and Inner Mongolia.In south China,the soil physical and chemical properties,ecological environment and farming system are different from those in one season crop area.The mechanism of continuous cropping obstacles is still unclear.In this research,the effects of continuous cropping and rotation on soil physicochemical properties and biological characteristics of potato growing areas in south China were studied by using methods such as metagenomics sequencing.The mechanism of potato continuous cropping obstacles in south China was also analyzed.These results will provide theoretical reference for continuous cropping obstacle intervention and suitable rotation mode selection.Moreover,the effects of rice-potato rotation system on the soil borne disease powdery scab and potato mop top virus(PMTV)transmitted by it were studied,the screening of disease-resistant varieties was carried out in the field and a sensitive and reliable detection method of PMTVwas established,these results will provide variety selection and technical reference for PMTV control in main potato production areas in south China.1.Effects of continuous cropping on potato yield,soil physical and chemical properties and microbial community structure in southern China.The physical and chemical properties,enzyme activities,soil microbial community structure and potato yield of newly reclaimed soil(N),first season soil(F)and continuous cropping soil(C3and C4)were compared.The results showed that:(1)The yield of the first season potato planted in N soil in was 2912.5 kg/666.7m~2,which was significantly higher than that of the fourth season potato planted in the C3 soil.(2)With the increase of continuous cropping times,soil pH,total nitrogen, organic matter,alkali hydrolyzed nitrogen decreased significantly,total phosphorus,available phosphorus and available potassium increased.The total number of soil radiobacteria decreased significantly,the ratio of total number of fungi to total number of bacteria,invertase and catalase activities increased significantly.(3)Continuous cropping of potato significantly changed the community structure and relative abundance of bacteria and fungi in soil.Potato continuous cropping reduced the diversity and richness of soil bacterial and fungal communities.The relative abundance of C and N-related dominant functional genera increased in continuous cropping soil.The pH and AN,TN and OC contents were the soil physical and chemical factors affecting the soil bacterial abundance,diversity and community structure of continuous cropping potato.The pH and AP,TP,TN and OC contents were the soil physical and chemical factors affecting the soil fungal abundance,diversity and community structure of continuous cropping potato.2.Effects of different rotation systems on potato growth,soil physical and chemical properties and microbial community structure in southern ChinaThe soil physical and chemical properties,soil microbial community structure and potato growth were compared between potato-rice rotation and potato-maize rotation.The results showed that:(1)the potato yield of potato maize rotation was 2804.94 kg/666.7m~2,which was significantly higher than that of potato rice rotation.(2)The pH and fertility level of soil in which maize was harvested in potato-maize rotation were significant than those of soil in which rice was harvested in potato-rice rotation.There was no significant difference in physicochemical properties between PMP soil and PRP soil after potato having been planted.(3)The community structure and relative abundance of bacteria and fungi in soils of potato-maize rotation and potato-rice rotation were significantly different.The bacterial diversities of PR soil and PM soil after rice and corn having been planted were significantly higher than those of PRP soil and PMP soil after potato having been planted.At the same time,the bacterial diversities from PR soil and PRP soil were higher than those of PM soil and PMP soil,respectively.The fungal diversity of PR soil was significantly higher than that of PM soil,and the fungal diversities of PRP soil and PMP soil were between those of PR soil and PM soil.Significant increases of the abundance of Alternaria,a potential pathogenic strain,and Penicillium and Mortierella,potential beneficial bacteria,were observed in PMP soil and PRP soil after potato having been planted.3.The effect of rice potato rotation on the occurrence of soil borne virus PMTV and the establishment of real-time fluorescent RT-PCR detection method for PMTVA new SYBR Green qRT-PCR method was developed to detect PMTV in potato tubers.The sensitivity of SYBR Green qRT-PCR was 10~5 times higher than that of conventional RT-PCR and100 times higher than that of nested RT-PCR.The progeny tubers infected with PMTV were 100%positive by SYBR Green qRT-PCR.The progeny plants exhibited foliar symptoms including chlorosis and reduction in leaf size when the PMTV-positive tubers were planted in a growth chamber at 20-22°C.These results proved that PMTV could be transmitted to the progeny plants through seed tubers.In the paddy field with powdery scab and PMTV,the incidence rate of tubers with PMTV symptoms was significantly reduced after rotation of two season rices.The rice potato rotation system could eliminate the powdery scab and its transmitted PMTV in a short time.Eleven varieties were screened in the paddy field with powdery scab and PMTV.Athough all the varieties were shown being infected with PMTV virus by n RT-PCR,the tubers of 9 varieties did not show PMTV symptoms. |
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