Studies On Biological Characteristics And Toxin Of Rice Spikelet Rot Disease (Rsrd) Pathogens Fusarium Spp

In recent years, there generally occurs a disease in the rice planting area around China, which seriously damages the panicle and grain of rice, and we generally call it the rice spikelet rot disease (RSRD). This disease is caused by a variety of fungi, and could cause the spoiling, discoloring and deformity of rice grains, so the setting percentage may be reduced and it will have a strong impact on the rice production. At the same time, the rice grains probablely be debased because of the pigment and toxin produced by the pathogenic bacteria.In this study, infected rice spikelet samples were collected from Hangzhou and Jiaxing cities, Zhejiang province, and216strains of Fusarium spp.were isolated, and identified by morphological and molecular biological methods. They could be totally divided into five species. Biological characteristics, fatty acid profile, toxin-producing ability, toxicity of crude toxin, and the management of the RSRD were also studied. The results are as follows:1. Isolation and identification of RSRD pathogenic pathogens.216strains of Fusarium spp. was isolated from infected rice panicle samples. They were identified and divided into five species, such as F. proliferatum, F. fujikuroi, F. verticillioidess, F. oxysporum, and F. graminearum. Among these216strains,, there were137strains of F. Proliferatum, accounting for63.4%,50strains were F. fujikuroi, accounting for23.1%,21strains belong to F. verticillioidess, accounting for9.7%,5strains of F. oxysporum, accounting for2.3%, and only3strains of F. graminearum, accountingfor1.4%. The pathogenicity of all isolated strains was proved according to Koch’s postulates.2. Biological characteristics of the Fusarium species.The optimum condition of F. graminearum growth temperature is25℃, pH is6, the best carbon source is glucose and sucrose, and the best nitrogen source is urea and sodium nitrate. The optimum growth temperature of F. oxysporum is25℃, pH is6, the best carbon source is glucose and sucrose, and the best nitrogen source is sodium nitrate. The optimum growth temperature of F. proliferatum is25℃, pH is6, the best carbon source is sucrose and glucose, and the best nitrogen source is sodium nitrate and sodium nitrite. The optimum growth temperature of F. fujikuroi is25℃, pH is8, the best carbon source is glucose, and the best nitrogen source is sodium nitrate. The optimum growth temperature of F. verticillioidess is25℃, pH is8, the best carbon source is sucrose, glucose and fructose sugar, and the best nitrogen source is sodium nitrate and urea.3. Fatty acid profile analysis of the Fusarium species.36kinds of fatty acids of the isolated Fusarium were analyzed by the sherlock fatty acids identification system. The fatty acids of Sum In Feature3,16:00, Sum In Feature5,18:1w9c and18:00are the main fatty acids. The cellular fatty acids profiles of these five Fusarium species showed differences but not significant, and the difference was not enough for Fusarium spp. Identification.4. Pathogenicity of the Fusarium species.The pathogenicity of F. fujikuroi is the strongest, F verticillioidess, F. proliferatum and F. graminearum are at second place and F. oxysporum is the weakest.5. Toxin-producingcapacity of the Fusarium species and toxicity of the crude toxin.The best toxin-producing conditions for F. graminearum, F. oxysporum and F. proliferatum were the Richard medium, temperature of25℃, pH of6, and cultivation for15days. Similarly, for F. fujikuro and F. verticillioidess, the best conditions were Richard and PD mediums, temperature of25℃, pH of8, and cultivation for15days. Studies on the effect of crude toxin against rice seedling showed that the toxicity of F. fujikuro crude toxin is the strongest to rice, and the toxicity of F. oxysporum crude toxin is the weakest.The fumonisin content in the crude toxin of F. fujikuro is the highest whichreached5379.03ppm (μg/g). F. verticillioidess’s takes second place, and the content is638.62ppm. F. graminearum’s takes third place, and the content is139.39ppm. In F. proliferatum, the content is13.87ppm, yet in F. oxysporum, the fumonisin content is the least and it is only 2.16ppm.6. Prevention and control of the rice spikelet rot disease in the field.The control efficiency is the best and could be up to45.06%， when20%isotianil suspension liquid spraying a time both in the tillering stage and booting stage. The control efficiency is not that ideal and only27.99%, when using both25%prochloraz and15%triadimefon spaying a time both in the booting stage and full panicle stage. The control efficiency is the worst and only0.08%, when using both25%prochloraz and50%carbendazol wettable powder spaying a time both in the booting stage and full panicle stage.