The Study On The Suppressive Effect Of Compost Against Fusarium Wilt Of Cucumber And Its Mechanism

Fusarium wilt of cucumber which caused by the soil-borne pathogen Fusarium Oxysporum f.sp. Cucumerinum is the main disease in cucumber production. With the protection of soil, the pathogen can survive to a long term, repeately infects the plant host and results in serious economical losses. Due to the lack of effective chemical fungicides and resistant varieties, fusarium wilt has become the limiting factor in cucumber production.A lot of practices and researches showed that compost can not only provide nutrition to plants, but also suppress the occurrence of various soil-borne diseases. However, due to the complexity of raw materials, composting process and different pathogens-plant systems, the suppressive effects of composts are varied. Until now, there are no standardized production and evaluation criteria for suppressive compost. Most scholars believe that the use of short-term pot experiment is the best way to verify the disease suppressive ability of composts.Based on our previous studies on the detoxication and stablization of sludge and pig manure by composting, the aim of this study was to analysis the possibility of using the compost to partially substitute peat growth media for cucumber cultivation and their suppressive effects on the cucumber wilt which caused by Fusarium oxysporum. The results were listed below:(1) Sludge and manure compost can suitably substitute 20%(V/V) peat for cucumber production under the non-pathogenic conditions. Both composts can stimulate the growth of cucumbers seedlings and the 20%addition volume will not cause toxicity to cucumber seedlings.(2) Under the artificial inoculated condition, the sludge compost was highly suppressive to the pathogen, which could reduce 85%of the disease severity compared to the peat control. Although the manure compost can slow development of the disease, the suppressive effect was week in the end. Considering the high disease pressure in this study, we believe that the sludge compost can effectively control this disease under the actual disease pressure. (3) The addition of composts changed the physical, chemical and biological properties of the growth media. The sludge compost amended media was acid and maintained a low level of NH4+-N, while the manure compost amended media was alkaline and the NH4+-N was high. The addition of composts enhanced the microbial biomass, microbial activity and the density of culturable microbial organisms. PCR-DGGE analysis showed bacterial and fungal communities undergone a shift after the amendment of composts. There was a significant correlation between the fungal community and disease severity. Clone analysis revealing the presence of non-pathogenic Fusarium oxysporum. Thus, the characteristics of the disease suppressive sludge compost can be summarized in the following three aspects:1) lower level of NH4+-N; 2) higher microbial activity and diversity; 3) the existence of non-pathogenic Fusarium oxysporum.