| Five thousands two hundreds and sixty-seven bacterial isolates were isolated from 510 rice samples of leaf, sheath, seed of 10 rice varieties collected at the different growing stages, and screened for antagonist against ustilaginoidea virens, the causal organism of false smut of rice in vitro. It showed that 245 bacterial isolates, 4.65% of total, were antagonists and sixty-three were strong against the pathogen. Ten isolates (7 Gram negative 3 Gram positive) selected, were identified by Biolog. Six belong to Pseudomonas with above 0.50 Biolog similarity, and one to Enterobacter, one to Bacillius and two to Corynebacterium with the similarity below 0.50. Further study showed 3 strains of Pseudomonas (22, 33 > 19) and 1 Gram positive, strain 58, can promote the root length and increase the dry weight of seedlings. Two Pseudomonas strains (22, 33) were evaluated for management of false smut in the field. The control effectiveness was 38.19% and 34.26%, respectively and significantly higher than the check.The study on the relationship between the total bacterial number and antagonists in different rice varieties showed that in general, the total bacterial number was the highest around the tillering stage and then decreased with rice mature. The rice sheath supported the highest bacteria number and the lowest in the seed. However, the percentage of antagonists was the highest in seed and the lowest in leaf. It was higher after heading stage than that before heading stage. Among the ten rice variety, Bing 98110 ^ Bing 9914 > Bing 9642 had the higher percentage of antagonists, while Bing 9759 > Xiu-shuil 1, Xiu-shui 1067 were lower. Based on the absolute number of antagonists, it was relatively stable in seed at different growing stages of rice. In leaf and sheath, the higher number hold at the tillering and dough stage. The 10 varieties can be divided into three group based on the distribution patterns of antagonists at the growing stages. The group 1 is Bing 98344 and Bing 9759, which reach the highest number of the antagonists at heading stage; group 2 is Xiu-shui 1 land Xiu-shui 1067, which show the higher number before heading stage andmaintain similar number in other stages; group 3 consists of the 6 varieties, which exhibits the highest number in the tillering and dough stage and the lower number in other stages. The data also indicate that it seems no closely relationship between variety resistance, total amount of bacteria and antagonists of ustilaginoidea virens.Field survey of false smut on yield components of different varieties showed that the diseased plants significantly increased percentage of empty grains from 2. 62% to 14. 88 % and decreased 1000- grain weight from 2.79% to 15.18%. The diseased seeds not only significantly affected the percent of seed germination but also reduced the dry weight of the seedlings. Natural infection of false smut for field evaluation of resistant varieties showed that Xiu-shui 11 and Xiu-shui 1067 were resistant to the disease, while Bing 9642 and Bing 98110 were severely infected. Sowing date can significantly affect the disease incidence. The experiment of the fungicide evaluation showed that the Ec50 of Wenqukedi, Kebo, Baosuining and Quwenxing was 0.927, 1.461, 3.262 and 5.006, respectively. The control effectiveness of Wenqukedi and Kebo in the field was 72.98% and 62.68%, respectively. |
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