Genetic Diversity And Pathogenicity Of Alternaria Spp.in The Invaded And Uninvaded Area Of Ageratina Adenophora In Southwest China

Fugus Alternaria is one of the most common pathogenic fungi in the world.Currently the studies on Alternaria have focused on those isolated from ornamental plants or crops,and rare report has been performed on exploring the differences of Alternaria communities between on the invasive and native plants.In this study,the diseased leaves,healthy leaves of the invasive plant Ageratina adenophora,as well as the diseased leaves of native plants from Yunnan,Guangxi,Guizhou,Sichuan and Hubei province were collected.The fungal strains were isolated from these collected leaves,and Alternaria spp.were selected for the further research.The Alt-a1 gene,adenosine triphosphatase gene(ATPase)and calmodulin gene(calmodulin gene)of all strains were amplified.Then the concatenated sequences were clustered into operational taxonomic units(OTUs)and performed phylogenetic analysis.According to the OTU classification,one strain was selected from each OTU to test the pathogenicity on A.adenophora,the corresponded host,and nine local plants in Kunming.Meanwhile,the morphology of these strains were also observed.The main findings and conclusions were obtained as follows:1.Alternaria spp.isolated from Southwest China was rich in species diversity.In total,167 strains of Alternaria were divided into 103 OTUs,phylogenetically including Alternaria citriarbusti,A.jacinthicola,A.tangelonis,A.pulvinifungicola,A.grossulariae,A.brassicinae,A.mali,A.rhadina,A.daucifolii,A.herbiphorbicola,A.nelumbii,A.citricancri,A.citrimacularis,A.resedae,A.steviae,etc.The numerically dominant OTU1 was found in A.adenophora and native plants in areas with different invasion history,however,their phylogenetic position remained unclear(Fig.2,Fig.3,Fig5).2.The phylogeny of Alternaria spp.isolated from different sources is relatively close.The results showed that the species composition of Alternaria spp.from different invasion history and host source was not significantly different.Some of them are potential new species.3.Alternaria spp.isolated from Eupatorium adenophorum may be potential pathogens of native plants.According to the results of pathogenicity test,it can be seen that the Alternaria spp.has strong pathogenicity to some local plants,such as Fallopia muLtiflora(Thunb.)Harald,Hypoestes triflora Roem and Ampelopsis Michx.Alternaria spp is the dominant endophyte of Eupatorium adenophorum,there are some ecological risks.(Fig.7).In conclusion,the results will facilitate people to understand the effects on the species composition of Alternaria and potential ecological risk driven by A.adenophora invasion.Meanwhile,the data will provided clues for exploring the role of fungi in the plant invasive process in future.