Biological Characteristics,Pathogenicity And Genetic Diversity Of Ustilaginoidea Viren

False smut rice was rice panicle stage disease caused by Ustilaginoidea virens, it had been lack of attention, because it only happened in late rice in the past a few years. False smut rice affected yield and quality of the rice. Along with the rice fields using of nitrogen fertilizer increased and planting large area of the late mature varieties type of big panicle and intensive panicle, false smut rice increased year by year, it had become a important disease which threatened high and stable yields of rice.The sporulation, growth rate, pigment, suppressing rate to germination of wheat seed, four factors, and pathogenicity of100isolates to Ustilaginoidea virens were analyzed by using SPSS software.Pathogenicity of100isolates were claasied into three typies according their pathogenicity (susceptible or reisitant) to rice cultivars, Liangyoupei9. First group is that isolates with weak pathogenicity, their average disease spike ratio is from0.1%to1%; the second group is that isolates with medium pathogenicity, their average disease spike ratio is from1%to10%; the last, these isolates exhibited stronger infection activities, their average disease spike ratio is more than10%.The sporulation of100Ustilaginoidea virens isolates showed appearently different.24of them can not produce spores;12of them can produce a liltte spores(betweenl-50×104per/ml);46of them have medium sporulation ability (50-250×104per/ml);30isolates exhibited strong sporulation acitivity (more than250×104per/ml).The growth characters of100Ustilaginoidea virens isolates were also analyzed.100isolates of U. viren were classed into three typies according their growth ratio in PSA meidium.6isolates belong to slowl group (<1.5mm/d);88isolates belong to medium growth group (1.5-3.0mm/d); the lest6strains grew quickly (more than3.0mm/d); Investigation of back colony of the isolates, there were in different clour.27isolates were in white,11isolates were in yellow,33of them were in yellow green;29of them were in green to dark.U. virens also exhibited biological activity to inhibit the root growth of wheat seed.22isolates exhibited high suppressing activity compared with control (inhibition ratio was more than50%):62isolates inhibition ratio is between20%-50%;16isolates exhibited low suppressing activity (Inhibition ratio was less than20%).The relationship of pathogenicity with the sporulation, pigment or growth activities was analyzed. The results indicated that pathogenicity is negative relevance with the growth ability, while is medium relevance with the sporulation of U.virens, and low relevance with the pigment of U.virens. However, there is no relevance between suppressing activities to the root growth of wheat seed and pathogenicity.150Ustilaginoidea virens were collected from9province of China. We analyzed their sporulation abilities. The results showed that132can produce conidia with88%in all isoaltes. We inoculated these isolates to the susceptible rice cultivars, Liangyou peijiu, the average disease index was67.3. we found that more of them can caused rice false smut, their disease index were more than50; Huaidao No.5, a medium resistance variety to rice false smut, the average disease index was21.80; Wuyujing No.3with resistance to rice false smut, the average disease index was16.07after artificial inoculation. According their pathogenicity to three rice cultivars,150Ustilaginoidea virens were divided into7races.36isolates of U.virens in race1, which had pathogenicity to above three rice varieties;53isolates of U.virens in race3, Liangyou pei9exhibited suspectible, while Huaidao No.5and Wuyujing No.3were resistance.48isolates of U.virens were collected from Xuzhou, Suzhou, Nanjing, Yancheng and Nantong and analyzed their genetic diversity and pathotype variability by using rep-PCR techniques. Genomic DNA from48strains was amplified with three specific primers of BOX, REP and ERIC. Dendrograms were generated from the data by using UPGMA analysis. The strains tested were classe into4,4and5clusters based on the PCR results of BOX, REP and ERIC at the level of90%similar, respectively. Genetic diversity of strains was maximum (0.55), classification of cluster group was significantly associated with origin of isolates; Primer used in BOX is suitable than the other two primers. The genetic diversities of the U. virens population were0.54(in BOX),0.44(in REP) and0.47(in ERIC), respectively. The results indicated that the genetic diversity of Ustilaginoidea virens was not various.48isolates were inoculated on susceptible rice cultivar,Liangyoupeijiu, there are three pathotypes. The predominant exhibited weak pathotype (occupied more than 50%). The relationships of UPGMA groups (BOX,REP and ERIC) between the pathotypes with the regional origin of strains is no significant correlation.