Fusarium Species Causing Rice Bakanae Disease And Resistance Of The Pathogen To Fungicides In Jiangsu Privince

677 samples of rice bakanae disease were collected frome 13 areas of Jiangsu Province, China and 548 isolates were achieved. These isolates were identified six Fusarium species such as F. moniliforme (50.55%), F. nivale (24.64%), F. semitectum (7.30%), F. graminearum (6.75%), F. lateritium (6.20%), and F. oxysporum (4.56%). Except that F. nivale was a main species in Xuzhou, Changzhou and Yangzhou, F. moniliforme was principal in other areas of Jiangsu.According to the inspection on the media supplemented the fungicid of 10 μg/ml(MIC) and 525 isolates were resistant to carbendazim, with average rate of 95.80%, and the rate of resistant isolates was 100% in 7 areas such as Suzhou, Wuxi, Zhenjiang, Nanjing, Yangzhou, Lianyungang and Huaian. Of the resistant isolates, High resistant ones(MIC> 100μg/ml) and made up 82.67% while moderately resistant ones(50μg/ml50) and 0.85μg/ml (MIC) according to EC₅0 value distribution of 30 isolates. Based on the inspection by the media Supplemented the fungicide of 3 μg/ml (MIC), there were 8 isolates resistant to prochloraz, and the proportion of isolates was averagely 1.46%. Of 8 isolates, 3 ones were high resistant, which was 103.07-126.20 times the sensitive threshold, and 5 ones were moderately resistant, which was 24.62-94.99 times the sensitive threshold. The resistance to prochloraz decreased significantly after the resistant isolates were 5²0 times transfered from tube to tube.The sensitive threshold of the pathogen to diisothiocyanatomethane was 1.265 ± 0.014μg/ml(EC5o) and 3.13μg/ml(MIC) based on the same method. But no isolatesresistant to diisothiocyanatomethane were found according to the inspection on the media supplemented the fungicide of 5μg/ml(MIC).Although there were a lot of differences in mycelial growth, ability of conidial and perithecial formation, and pathogenicity to rice plants among the isolates in nature, these features of isolates were not obviously correlative with the resistance to carbendazim and prochloraz.The inoculation of mixed conidia(1:1) fromresistant and sensitive isolates showed that the isolates resistant to carbendazim had stronger competition than the sensitive ones in or on rice plants, which might be an important reason for the pathogen to have high resistance to carbendazim and carbendazim-like fungicides to control rice bakanae disease would be dangerous in the field. On the contrary, the isolates resistant to prochloraz had lower competition than the sensitive ones in or on rice plants, which showed the resistance of the pathogen to prochloraz in the field would be slowly increased. But the supervision of the resistant development of the pathogen to prochloraz would be required because a few of isolates with high resistance to rhe fungicide occurred.