Community Composition And Genetic Diversity Of The Insect Pathogenic Fungi Metarhizium From Soils Of Different Habitats

The ascomycete Metarhizium genus consists of several species of entomopathogenic fungi that can parasitize a broad range of arthropods and can be used as biocontrol agents against plant-feeding and blood-sucking arthropods.Knowledge of the natural occurrence and community structure of Metarhizium in diverse habitats is important to understand their ecological role.In this study,the community structure and genetic diversity of Metarhizium from soils of four habitats,representing woodland,grassland,cropland and orchard,was evaluated by using multilocus microsatellite(or simple sequence repeats,SSR)genotyping and EF1-? gene sequencing methods.A total of 320 soil cores [(eighty soil cores along four parallel transects of 100 m(20 cores per transect)in each habitat)] were analyzed.The results are shown as follows:A total of 521 Metarhizium isolates were obtained,identified as five species,i.e.,M.anisopliae(86 isolates),M.majus(2 isolates),M.pingshaense(412 isolates),M.acridum(7 isolates)and M.guizhouense(14 isolates).In all,69 multilocus genotypes(MLGs)and 19 EF1-? haplotypes were detected from microsatellite and sequence analysis.The number of Metarhizium species present in the woodland,orchard,cropland and grassland was 4,3,3 and 2,respectively.M.acridum was found only in the woodland,while M.guizhouense was detected only in orchard.Among all isolates,the highest genetic diversity of SSR and the highest nucleotide polymorphism of EF1-? sequences was from woodland(h=0.690,and ?=0.01443),while the lowest h and the lowest?was presented in orchard(h=0.167,and ?=0.00376).M.pingshaense was detected among all habitats as dominant species.Thirty-three MLGs and 9 EF1-? haplotypes were revealed among isolates of this species.The population genetic diversity inferred from SSR data for this species ranged 0.032-0.566.The coefficient of gene differentiation(Gst)was 0.488,indicating that more than half of the genetic variation of M.pingshaense accounting for among individuals within populations.PCoA of M.pingshaense SSRs showed that all isolates from woodland exhibited two distinct groups,one presented a closer relationship with isolates from cropland,grassland and orchard,than the other which consist of the rest isolates from woodland.The phylogenetic tree inferred from EF1-? sequence analysis presented similar result,which indicated great genetic divergence among M.pingshaense isolates within the woodland population.The monophylogeny of M.anisopliae,M.majus,M.pingshaense,M.acridum and M.guizhouense and the detection of 19 haplotypes among the five species inferred from EF1-? sequence indicated that EF1-? sequence marker is efficient in the interspecific phylogenetic resolution of the genus Metarhizium,or even partly efficient at the interspecies level.The fact that no MLG was shared by all of the 4 habitats suggested that microsatellite markers be capable of detecting genetic variation among conspecific strains.In summary,the woodland,grassland,cropland and orchard harbour diverse populations of Metarhizium.Geographical locations,climate conditions,habitat(plant vegetation)types,etc.may play important roles in determining the community structure of.High genetic variation present in the dominant species M.pingshaense among the four habitats suggests this species may have great potential adaptation to wide range of distribution.The application of combining SSRs markers and EF1-? sequence analysis proved an ideal tool for the population genetic study of Metarhizium resources.