Studies On The Isolation And Identification Of The Pathogen Of Xiang Lotus Rot Disease And Control Of The Disease

Lotus (Nelumbo nucifera) is a known perennial aquatic plant, which possesses high ornamental value, nutritional value, medicinal value and economic value. Lotus rot disease is one of the most serious diseases of lotus, which leads to severe yield reduction even extinct. Xiang lotus, a local variety of Xiangtan City Hunan Province, is the produce with a lot of value to develop. For now, rot disease of Xiang lotus has become a worsening problem, leading to a sharp decline in the output of the lotus. To find the way of controlling the disease, the pathogen was isolated and purified from the Xiang lotus with rot disease, and was classified and identified through morphological observation, pathogen ITS sequence analysis and applying of Koch’s postulates. Moreover, the antimicrobial effect of main chemical pesticides in the market and the biocontrol bacterium strain X23was detected and confirmed in the field. The research results in this paper are as follows:1. The pathogen of Xiang lotus rot disease was isolated and identified. The pathogen strains were isolated and purified from the diseased Xiang lotus grown in Xiangtan County, and were identified as Fusarium oxysporum in Deuleromycotina through the observation of morphological characteristics, blast and analysis the ITS sequence of the strains and applying of the Koch’s postulates.2. The antimicrobial effect of frequently-used chemical pesticides and the biocontrol bacterium strain X23to Fusarium oxysporum was determined. The antimicrobial effect of6kinds of frequently-used chemical pesticides was detected through mycelium growth rate method, and their toxicity regression equation was calculated. In these6pesticides, carbendazim is the best fungistat, however, thiram is the worst. Confronting culture test showed that the biocontrol bacterium strain X23has good inhibition effect on Fusarium oxysporum.3. Control effect of5chemical pesticides and4biocontrol reagents against Xiang lotus rot disease was tested in the field and their effect to yield was also detected. At the end of spring and the beginning of summer in2013, the temperature and rainwater in Xiangtan City were higher and less, respectively, than former years. Therefore, conditions against growth of Fusarium oxysporum leaded to no occurrence of Xiang lotus rot disease this year. However, the results of yield measurement showed that the application of biocontrol bacterium strain X23enhanced yield of Xiang lotus, which the yield of experimental plot applied X23is30.76%more than the untreated plot applied with conventional pesticides, respectively. Also, the application of biocontrol strain X23can delayed the senescence of Xiang lotus by20days. The results of plot showed that the application of X23has a role in promoting growth, anti-aging and increasing production for Xiang lotus. Moreover, the chemical reagent Mancozeb also enhanced23.07%yield comparing with the untreated control applied conventional pesticides, respectively.