Effect Of Fungicides On Don Production By Fusarium Graminearum

F. graminearum (teleomorph, G. zeae) causes head blight of cereals and contaminates grains with trichothecene mycotoxins that are harmful to humans and domesticated animals. Various strategies have been developed to control Fusarium head blight (FHB) and to reduce DON contamination of cereals, with chemical control having an important role in an integrated FHB control program. Control of FHB relies on carbendazim (MBC) in China, but resistance to MBC in F. graminearum is now widespread, and the resistance of MBC could have effect on DON production of F. graminearum. Therefore, there is a challenge now to find alternative fungicides for MBC in China. JS399-19,(2-cyano-3-amino-3-phenylancryic acetate) is a novel cyanoacrylate fungicide introduced by Jiangsu Branch of National Pesticide Research&Department South Center. This fungicide was demonstrated to have activity against Fusarium. spp, especially for Fusarium graminearum. There is no JS399-19resistance in field, but JS399-19resistant mutants were easy recovered from wild-type strain by ultra-violet (UV) irradiating and fungicide training with high frequency. The results also revealed that most of the resistant mutants belong to MR or HR. There are no data on the effect of JS399-19-resistance on DON production by F. graminearum strains. So the major results of the present study are shown as below.We used real-time quantitative PCR (RQ-PCR) and gas chromatography with electron capture detector (GC-ECD) to evaluate the DON production ability of different kinds of strains in shake culture or in the field. The strains included four MBC-resistant site-directed mutants at codon17,50,198,200in β2-tubulin, and their MBC-sensitive progenitor strain2021. We found that MBC resistance increased DON production ability in shake culture or in the field. But different DON production abilities of mutants were not related to the level of MBC resistance. Comparing the abilities of2021and mutants DB6(β1-tubulin-directed), ND23(β2-tubulin-directed) and their revertant strains Bt2021d, nt2021b, respectively, we also found direction of β2-tubulin could reduce the abilities of strains, but no difference was found between DB6and2021. Tri5gene expression increased in MBC-resistant strains grown in shake culture, but reduced in β2-tubulin-directed strain ND23compared with their progenitor strain2021. There was also a significant exponential relationship between DON production ability and Tri5gene expression. In shake culture, MBC could significantly reduce DON production abilities of F. graminearum.Different kinds of strains were evaluated for DON production ability in shake culture or in the field. The strains included three JS399-19-resistant mutants Y、B、C, their JS399-19-sensitive progenitor strain2021and the JS399-19-sensitive strain5-9which was reverted from resistant mutant Y-A. We found that JS399-19resistance increased DON production ability in shake culture or in the field. However, the abilities of DON or total DON toxin production in5-9were significantly reduced compared with resistant mutant Y-A. Tri5gene expression increased in JS399-19-resistant strains grown in shake culture. These results suggested JS399resistance would enhance DON production ability of strain. Nevertheless, the abilities to product DON of resistant mutants were significantly reduced with the treatment of JS399in EC50or EC90dosage and it indicated that the use of JS399could effectively control the abilities to product DON of strain.Evaluate the efficacies of kresoxim-methyl used with MBC, a mixture of tebuconazole and thiram, tebuconazole and thiram mixture used with MBC and JS399-19on the development of FHB and DON contamination of winter wheat in Bai ma hu farm of Jiangsu province in2010. The incidence of spikelets infected (ⅡS), thousand grain weight and trichothecenes toxins concentration were quantified. Four methods could significantly reduce IIS of FHB, and trichothecenes toxins within the grain and tebuconazole and thiram mixture used with MBC was the best. However, JS399-19had best effect on controlling DON accumulation within the grain.The occurrence of trichothecene toxins was also determined in different kinds of wheat-based foods (convenience noodles, biscuits, bread, and cakes) in Nanjing, China. A total of59commercially available samples were collected from the supermarkets in Nanjing from December2010to July2011. Four trichothecenes toxins were detected and quantified by gas chromatography with electron capture detection. The content range of DON was0.01-1.89mg/kg, and twenty-seven of59samples contained more than1mg/kg of DON, which is the regulatory limit defined by the Chinese government.