Biological Activities Of Azoxystrobin To Plant Pathogenic Fungi And Resistance

Azoxystrobin,developed by Zeneca company, was the first product of the strobilurinfungicides, and combines high levels and broad sprectrum of fungicidal activity withexcellent safety in the wnviroment, The fungicidal activity stems from the fact that theyinhibit mitochondrial respiration in fungi by at a specific site on comlex lIl. However, theresistance to the strobilurins occurred 2 years atier the fungicides were introduced into themarket. In 200l, azoxystrobin was registered for use in China, so it is essential to embarkon biological activity of azoxystrobin to pathogenic tlingi and resistance in China.Writer isolated and characterized l4 pathogenic tlingi in the field, and determinedactivity of azoxystrobin. The result showed that azoxystrobin had strongly fungicidal andfungistatic activity to lots of ft1ngal pathogens and azoxystrobin inhibited mycelia growthas well as conidia germination. Mycelia growth of MagaPorthe grisea Gibberellafujikurio, Rhizoctonia solani, Gibbere lla zeae, Colletotrichum twnatium,Scler()liniusclerotiorum and C.gloeosPorioicles (red)was most sensitive to azoxystrobin,and Ii C5()values were 0.0256~ 5.06l8pg mL-l. In Boreytis.cinerea and Allernaria solani, theinhibiting activity to mycelia groWth was lowef, but it inhibited strong1y conidiagermination. Azoxystrobin provided exce1lent control of wheat powdery mildew andcucumber downy mildew. Azoxystrobin inhibited melanin biosynthesis of C. lagenatiumand A.solani; inhibited significantly conidia production of B. cinerea and sclerotiaproduction of Ssclerotiorum. The pathogenicity of C lagenatium and Bgraminis lost orreduced after treatment with low dosage of azoxystrobin.The paper study activity of azoxystrobin to twnaPothe gri3ea intensively andsystematically. Activity in vitro depended on the mount of ingredient in media, andfermentab1e carbon sources had antagonistic efTect on antiflingal activity ofazoxystrobin.Azoxystrobin strongly inhibited mycelia groWth, germination and conidia production, andaffected significantly conidia pathogenicity of M grisea. Azoxystrobin inhibited melaninbiosynthesis. In the pot, azoxystrobin had excellent systemic property, protective andcurative activity, and protective activity was prior to curative activity. Mannitol and SHAMhad no significant activities to azoxystrobin inhibiting mycelia growth, but had synergisticeffect on germination of azoxystrobin. Baseline sensitivities (EC5o) to azoxystrobin among63 isolates of Mgrisea was 0.00l0 ~ 0.0906pg mL-1, mean EC5o was 0.0223pg mL-l.Amistar fOrmulate was able to control rice blast in field, but the effect was insignificant.Formulate could improve the ytelds.Mutant B9-R2 of MagaPothe grisea was gained by ultraviolet radiation,and showedhigh Ievel resistance to azoxystrobin. Azoxystrobin-resistance of progenies was heritable.However, with subculture and incubation at low temperature, the level of resistance andrate of mycelia groWth reduced. Capacity of conidia production and germination reduced.Toxin production. melanin production and pathogenicity of mutant was the same as that ofB9. Azoxystrobin did not inhibit B9-R2 melanin biosynthesis, and did l1ot control thedisease caused by B9-R2 effectively in vivo.EC5o of azoxystrobin to l6 isolates of Collectot).ichllm gloeosPorioides ranged from0.0221pg mL-I to more than l00pg mL-1. EC5o of azoxystrobin to NJR isolate was0.2185pg mL-', and NJB isolate was insensitive to azoxystrobin. Both NJR and NJBiso1ates were more sensitive to carbendazim than other fungicides determined. Theinhibiting activity of azo-mixtures with carbendazim, chlorothaloni, thiram and mancozebto NJR and NJB isolates were significantly different. The results in vitro showed that themixture of azoxystrobin and carbendazim revealed additive bioIogical response to NJR andNJB isolates, and the mixture of azoxystrobin and chlorothaloni showed synergistic effectto NJB opposite to NJR isolate. T11e azo...