Detection Of Ustilaginoidea Virens And Resistance Evaluation Of Rice Cultivars Against False Smut

False smut (green smut) of rice, which was caused by Ustilaginoideavirens(cooke) Tak., is an important grain disease in rice production areas around theworld. In recent years, with the change of climate and rice varieties, the false smut hasbeen becoming seriously. The disease affects crops quality and reduces its yield. U.virens also produces ustilotoxin, which may be toxic to animal and human.The specific RAPD fragment of U. virens was collected, cloned and sequenced.Based on the sequence of RAPD marker, the SCAR primers were designed and thespecific RAPD fragment was successfully converted to SCAR marker of U. virens.The PCR product of all tested isolates from U. virens showed a clear and brightfragment with about257bp, but other pathogen had no any amplification fragments.The detection sensitivity was1pg DNA of U. virens. A nested PCR system for U.virens detection was also developed. The PCR product of all tested isolates of U.virens showed a specific fragment with about210bp by nested primers. Thedetection sensitivity was10fg of pathogen DNA. The sensitivity of nested PCR for U.virens was much better than the traditional PCR. These methods developed in thisstudy is effective to detect and identify the pathogen in plant and seed of rice．To know the effect of false smut on yield of rice and the resistance of rice newcultivars against this disease in Fujian province, the survey were made in the rice field.The results showed that the abortive grain rate and yield loss rate increased with theincrease of false smut ball number. When the numbers of false smut ball was over5per panicle, the loss rate of yield reached over35%. The resistance of58varietiesagainst U. virens was detected and evaluated by using artificial injected inoculationmethod in greenhouse and disease inducing method in field. The results indicated thatthere are3varieties among58varieties were moderate resistance, accounted for5.17%of tested varieties, such as Fufengyou366, Yueliangyou673and Guangyou7017,18varieties were middle susceptibility and37varieties were susceptibility,accounted for31.03%and66.79%respectively.The rice false smut disease incidence was obviously different among rice cultivars. We used some cultivars with different resistance level as materials,including Noxiang21(resistance), Fufengyou2(middle susceptivity), Fuliangyou366(susceptivity), Hua2hao3301（susceptivity）, Luyou313（resistance）andPujiang6（susceptivity）. The relationship between reproductive period traits of plantsand susceptivity of rice cultivars against disease were analyzed. The results showedthat there was no relationship between susceptivity of rice cultivars to disease andauricle space between sword leaf and next leaf, and days of booting and headingperiod. However, the susceptivity of rice cultivars may be closely related with panicletypes and the number of gains per panicle. Panicle type of resistant cultivars weresignificant more loose than that of susceptible cultivars，and the number of gains perpanicle and the yield of rice were higher in resistant cultivars than in susceptiblecultivars.