The Chemical Control Of Wheat Take-All And The Dsrna Virus In Gaeumannomyces Graminis Var. Tritici

Take-all is an important wheat disease in Huang-Huai wheat production regions of China. To screen fungicides to control wheat take-all, inhibition activity of8fungicides against Gaeumannmyces graminis var. tritici was tested. The results showed that the activity of mycelial growth inhibition of the8fungicides was as follows:prochloraz> difenoconazole>tebuconazole>myclobutanil>kresoxim-methyl>thifluzamide> fenoxanil>fludioxonil.The joint-toxicity of the mixure of difenoconazole and prochloraz, and difenoconazole and tebuconazole, against G. graminis var. tritici were tested. The results showed that the toxicity coefficient of all mixtures was within80-120, which mean that there are additive effect. The co-toxicity coefficient was112when difenoconazole and prochloraz were mixed at4:1, and it was111when difenoconazole and tebuconazole were mixed at1:1.The indoor pot experiments showed that the seed treatments by triadimefon and tebuconazole both had a good control efficiency of G. graminis var. tritici. However, the seed treatments by propiconazole had poorer performance. The fungicide spraying at the beg almost had no control efficiency (less than15%).Inhibition activity of difenoconazole aganinst92isolates of G. graminis var. tritici from different regions in Shandong, Jiangsu, Henan province was tested. The results showed that the EC50values of92isolates ranged from0.0485to0.5973μg/mL. No isolate insensitive to difenoconazole was detected, and the sensitivity frequency was distributed as unimodal curves, these values could be adopted as the sensitivity baseline for resistance monitoring. Twenty-two isolates of G. graminis var. tritici were random selected to test their virulence. The results showed that the virulence was different significantly among the isolates, and the virulence was not related to the hypha growth rate. The dsRNA in these G. graminis var. tritici isolated, and no dsRNA was detected from only five isolates. The virulence of some isolates was weak regardless of the dsRNA presence or absence. It suggested that the presence or absence of dsRNA had no obvious correlation with the virulence of isolates. The part of an RdRp gene was obtained and its amino acid sequence was highly homology to many plant endogenous viruses.