| Rice false smut is caused by Ustilaginodea virens(cooke)Tak.Recent years,Rice False Smut gradually has become one of the major diseases in r ice with cultivation of high yield hybr id rice and promotion of high yield cultivation techniques.It is important in rice false smut management to research the epidemiology of this disease.The epidemiologic factors were anlysed in this study,including meteorological factors,pathogen source and resistance of rice varieties,.And a white false smut ball strain was identified and its biological characteristics were analyzed.Detailed results were as follows.1、The field resistance of hybrid rice varieties from Zhejiang province were evaluated at Lin’an and Xingchang nurserys in this study.Results showed that field resistances of 26 hybrid rice varieties available in Zhejiang province,to rice false smut were evaluated in two natural disease nurserys located in Lin’an and Xinchang.Then,correlation of Field resistance and panicle traits and was analyzed in this study.Results showed that there was field resistance difference among 26 rice varieties in same infected field and between two disease nruserys.Effects of cultivars,locations and their interaction were all highly signif icant contribution to the variation in field resistance to rice false smut.Up on rice types,field resistance rice false smut was as follows: indica hybrid rice(IHR)> japonica hybrid rice(JHR)> indica-japonica hybrid rice(IJHR),and field resistance of IJHR was significantly lower than that of IHR and JHR.Correlation analysis results showed that disease severity of rice false smut to varieties was negative correlation with their panicle length,but the correlation coefficient not reach significant level(p=0.05),while it was significant positive correlation with primary branches,total grains per panicle and grain density.2、In Chayuan Rural Ninghai County,the relationships between rice false smut epdemic factors and incidence of rice were studied from2012 to 2015,though setting natural disease nursery and interval sowing.The results showed that from 2012 to 2015 in late August to rice maturity,a large number of rice aspergillus spores could be detected.In 2012 and 2014 the middle of June a small amount of rice aspergillus spores in the air were detected.However in the same period in 2013 rice aspergillus spores was almost undetectable.The relationship between number of spores and daily average temperature was highly significant negative correlation.However the relationships between number of spores and rainfall,relative humidity and wind speed average was negatively correlated,but the correlation coefficient were not significant.About the time of rice rupturing stage,the relative humidity was stable,basically in between 80% and 100%,which was beneficial to incidence of rice false smut.Temperature was the biggest factor affecting occurrence of false smut.At 28 ℃ to 20 ℃,with the temperature reducing the incidence of false smut of an upward trend,and drastic changes in temperature or below 20 ℃ was not conducive to the occurrence of rice false smut.Rice aspergillus spores had little effect on the incidence in air.As long as environmentally appropriate,small amounts of spores could induce large-scale outbreak of smut.3、Compared white false smut strain with normal strains,the results showed that rice panicle was infected by white false smut strain which led to rice diseased and similar ity degree of those strains’ conserved sequences were more than 99% and those strain were white false smut.The ability of pigment synthesis for white false smut strain was lost.The surface of chlamydospores from normal rice false smut balls was verrucose,while the surface of chlamydospores from white rice false smut balls was smooth.Except medium of 1/4SDAY,the growth speed of white rice false smut was faster than normal strains.But The white false smut strain’s sporulation was less than the normal strains’ in PSB.The study found that white rice false smut and normal rice false smut were not resistant strains. |
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