The Occurrence Of Aphid-pathogenic Fungi In Fujian Province And Biological Character Of Zoophthora

Entomophthorales fungi(Zygomycota, Zygomycetes)are widely distributed inthe world, and recognized as an important natural factor of pest populationcontrolling， of which the majority are obligate aphid pathogens. Aphids areworldwide pests and are feasible to be infected by over30species of fungalpathogens. Thus, more emphasis should be put on studying the biologicalcharacteristics of entomophthoralean and the epizootiology of aphid diseases causedby them, which plays an important role in biocontrol. This research systematicallyinvestigated the species, distribution and prevalence of aphid-pathogenic fungi inFujian Province, togethered with the experiment in which alataes from air capturesverified the hypothesis that entomophthoralean can disseminate within migratory hostinsects. During the period, we isolated certain number of strains and studied thebiological characteristics of two Zoophthora strains. The results were given asfollows：The results of the investigation and isolation of aphid-pathogenic fungiresources in Fujian Province Fujian Province, located in the south subtropical ofchina,was an ideal place to study entomophthoralean, due to its rainfall and mildclimate. From October of2011to December of2013, our group conducted fivesurveys in Fujian Province and found eight kinds of aphid-pathogenic fungi,identified as Zoophthora radicans, Pandora neoaphidis, Pandora nouryi,Conidiobolus obscurus, Conidiobolus thromboidos, Entomophthora planchoniana,Neozygites fresenii and Verticillium lecanii. Myzus persicae and Lipaphis erysim weretwo common hosts and could be infected by all the aphid-pathogenic fungi except N.fresenii. Z. radicans and P. neoaphidis were widely distributed throughout FujianProvince, however, the other pathogenic fungi were only found in some areas, forexample, E. planchoniana could be found easily in coastal cities. The overallincidence ratio of Z. radicans and P. neoaphidis was much higher than any otherpathogenic fungi. Z. radicans always occurred at the time when autumn ended andwinter started. To the contrary, P. neoaphidis always occurred at the end of winter and early spring. N. fresenii always occurred in the summer, and other pathogenic fungioccurred both in winter and spring. But Conidiobolus could not trigger any epizootic.We have obtained39pure strains in the laboratory by isolating from the samples ofinvestigation.Field inveatigation and pathogenic fungi within migratory alataes from aircaptures We chose the roof and the4th floor balcony of the chemical laboratorybuilding in Huaqiao University as platforms for trapping alates from September of2011to October of2013, and conducted field survey at the same time. During certain twoyears,1941alataes were trapped, including M. persicae, L. erysimi, Bravicorynebrassicae, and Aphis gossypii. These aphids were taken back to the lab andindividually reared on cabbage leaves for6days at20oC,12L:12D. Among them109alataes died of entomophthoralean which we identificated subsequently. Inaddition, P. neoaphidis and E. planchoniana were the dominant populations,accounting for50.4%and27.5%of total infections, respectively, followed by C.thromboidos(14.5%), p. nouryi(5%), Z. radicans(2cases) and N. fresenii(1case). Theresult of field investigation was in line with that of air captures. Furthermore, byobserving the reproductive capacity of the trapped alates, we found that the alatesinfected by entomophthoralean still had reproductive capacity, but much lower thanthe healthy ones.Biological character of Zoophthora This study selected SW1212strainsisolated from Fujian and MH1006strains isolated from Menghai in Yunnan asresearch objects to explore their growth, spore germination, sporulation, virulenceand the ability to survive in the wild. The results suggested that two strains had thesame optimum growth temperature (25oC), but SW1212growed faster and were ableto enlarge its colony by ejecting conidia as opposed to extending hypha as MH1006.Besides, the spore germination rate and respective virulence to their hosts were alsodifferent. With respect to SW1212strain, the spore germination rate could reach70%at25oC,100%RH and the maximum virulence to M. persicae approached to about95%, while the former of MH1006strain was only35%, the latter to leafhoppersonly about20%and the virulence to M. persicae was much lower, only about7%under the same conditions. In addition, through sporulation and releasing strains to the wild, we found that Zoophthora had a great potential for use in biological control,due to its high sporulation capacity and good survival in the field.In summary, this study had clarified the species, distribution and prevalence ofaphid-pathogenic fungi in Fujian Province and proved that Entomophthorales fungican be well adapted to subtropical climate and formed epizootic in local environment.Combined with the experiments that trapping alataes from the air, we further verifiedthe hypothesis that entomophthoralean can disseminate within migratory host insects.A lot of strains were obtained for following scientific researchs. We have figured outcertain characters of Zoophthora, including growth, germination and virulence, bystudying two Zoophthora strains isolated from different hosts, and thus itdemonstrated basis for further research of these starins.