Studies On Resistance Of Fusarium Graminearum To Carbendazim In Sichuan

Fusarium head blight (or wheat scab) is a serious disease of wheat around the world.It is also one of the three important diseases of wheat in Sichuan. Resistance tocarbendazim (MBC) has seriously developed in Fusarium graminearum in east of China.To determine the resistance of F. graminearum to MBC in Sichuan and to provide thescientific base for fungicide controlling and for monitor or forecast of MBC-resistance, weconducted the research and collected wheat samples showing symptoms of F. graminearumhead blight from 16 districts in Sichuan province from the year 2002 to 2006. The resultsof the research as follow:1. A total of 239 isolates of F. graminearum were collected to determine the frequency ofresistance to MBC. The critical concentration for resistance and sensitivity was 1.4μg/mLof MBC. The results showed that there were 39 MBC-resistant isolates existed, thepercentage of MBC-resistant was 16.32%. These resistant isolates were collected fromdistricts of Chengdu, Ya'an, Neijiang, Ziyang and Deyang. The values for 50% effectiveconcentration (EC₅₀) were identified by measuring mycelial growth in fungicide-amendedmedia. Average EC₅₀ of 100 sensitive isolates were 0.5870±0.0139μg/ml and those of 39resistant isolates were 0.6431±0.0362μg/ml. All of the resistant isolates were low-resistantto MBC.2. The results of fungicide cross-resistance test showed that EC₅₀ of MBC-resistant isolatesto thiabendazole were between 0.98190μg/ml and 1.2100μg/ml which were 2 or 3 timeshigher than MBC-sensitive isolates'. EC₅₀ to thiophanate-methyl were between 3.32859μg/ml and 4.25180μg/ml which were higher than sensitive isolates'. All theMBC-resistant isolates showed positive cross-resistance to thiabendazole andthiophante-methyl.3. The mutants of wild-type F. graminearum resistance to MBC were generation inlaboratory by fungicide taming and 12 mutants were collected. All of the mutants werelow-resistant to MBC. The result showed that F. graminearum could getfungicide-resistance while using MBC, but the level of fungicide-resistance of mutants wasuncertainties.4. Soluble protein and isoesterase patterns of MBC-resistant mutants and their wild-typesensitive F. graminearum were studied by polyacrymide gel vertical electrophoresis. Therewere no obvious difference of patterns between low-resistant mutants and wild-typesensitive isolates in soluble protein and isoesterase. The specific protein or esterase bandswhich were correlative to fungicide-resistance were not be found.