Resistance Of Fulvia Fulva On Tomato To Flusilazole

In this paper the resistance of Fulvia fulva to flusilazole, inducing resistance of sensitive isolates, biological characteristics of mutant-isolate and cross-resistance to other fungicides were studied. The level and distribution of F.fulva resistance in Liaoning, the fitness of mutants, the relation of cross-resistance between flusilazole and other fungicides were confirmed. It showed that the inherent risk of flusilazole to F. fulva is low. The results can support to build fungicide resistance management strategies and offer references to develop new fungicides. The results were as the follows:1. Two hundred isolates of F. in tomato was obtained in 2002 and 2003 from several main protection fields in Liaoning province. Sensitivity of these isolates to flusilazole was determined by the methods of mycelium growth inhibition. Four kinds of isolates were found, they are sensitive isolates, low level resistant isolates, moderate level resistant isolates, high level resistant isolates, the percentage of them was 42%, 47.5%, 7.5%, 3% respectively. Sensitive and low level resistant isolates are predominant isolates. Six high level resistant isolates were detected but the quantities and distribution is not abroad. The results showed that F.fulva in Liaoning hasn't developed severe resistance.2. Flusilazole-resistant mutants to F. fulva have been acquired by ultraviolet-inducing and chemical-traming and the two methods use together. The resistant level of mutants by three methods belonged -to low level resistance, moderate resistance and high level resistance respectively. This results showed that fungicide played an important role in development of resistance while ultraviolet is secondary. When used together they can accelerate the emergence of high level resistante isolates.3. Significant differences in mycelium growth, fresh weight and osmotic sensitivity were observed between sensitive and high level resistant isolates. This means the fitness of the high level resistante isolates decreased significantly. But the other kinds of isolates exhibited no difference with sensitive isolates. The resistance of mutants and field-mutants can't pass down stably, they can become sensitive isolates after they were continuously transferred in PDA medium without fungicide, but the high level resistante isolates is difficult to do this. The research indicated that the heredity of resistance in F. fulva to flusilazole is control by polygene. Mutants have lower competition capacity than that of sensitive isolates, and it is difficult to become predominant isolates.4. There was no cross-resistance between flusilazole and procymidone as well as azoxystrobin, carbendazim, whereas there was positive cross-resistance between flusilazole and myclobutanil as well as triadimefon. Azoxystrobin is a kind of effectivenew fungicide to control Fulviafulva and is good for spreading. 5. On the whole, we assumed that the inherent risk of flusilazole to F.fulva is low.