Studies On The Relationship Between Foliar Microflora And The Occurrence Of Camellia Gray Spot Disease

Camellia gray spot disease is one of the normal diseases that infect camellia,resulting in dry rot of leaves and tips.Light infection impacts the appreciation of a plant;serious infection may lead to the death of the whole plant.Therefore,such disease has become a major obstacle of production and development of camellia.Currently,there are many studies on microflora of plants,but rarely any research reports on camellia microflora.This thesis is to take the camellia leaves as the object of study,preliminarily investigates the relationship between infection of leaf gray spot disease and its micro-entironment,and provide basic information for prevention and cure of camellia gray spot disease by microecological control.Main results of study as follows:(1) Microflora of camellia leaves consists of bacterium,fungi and actinomyces.These three microbial species perch more on the healthy leaves than on the sick leaves.Among the phyllosphere microbes on the leaves,bacterium is most in quantity,fungi is less,and actinomyces is least;among the endophytic microbes in the leaves,fungi is most,bacterium is less,and actinomyces is least.(2) Give priority to morphological characteristics and by means of molecular biology, this test has identified microbes from the leaf surfaces:phyllosphere bacterium of 38 genura with 70 species,fungi of 27 genera with 45 species,actinomyces of 22 genera with 4 species; from the interior leaves,endophytic bacterium of 18 genera with 28 species,fungi of 18 genera with 23 species,actinomyces of 1 species.Dominant species have obvious differences between healthy and sick leaves.The phyllosphere dominant species,which play an important role on the composition of biomass and display steady behaviors on the leaves,are:Bacillus cereus,Cladosporium cladosporioides,Streptomyces griseus and Streptomyces mediolani;On the sick leaf surfaces there are:Stenotrophomonas maltophilia,Pestalotiopsis guepini and Streptomyces microflavus.The endophytic dominant species in the healthy leaves,which play an important role on the composition of biomass and display steady behaviors,are:Bacillus subtilis,B.thuringiensis,B.amyloliquefaciens;Botryosphaeria dothidea and Guignardia camelliae etc;in tne sick leaves,includ B.amyloliquefaciens,B.cereus,B.subtilis,fungi include G.camelliae and Pestalotiopsis guepini etc.(3)Seasonal changes have significant influence on the quantity and species richness of phyllosphere bacterium.Those changes also seriously impact the quantity of endophytic bacterium,but less influence on fungi and actinomyces.The quantity and species richness of bacterium reach their active peak in summer,but the activeness is very low in winter.Whether leaves are infected by gray spot disease has significant influence on the quantity and species richness of phyllosphere and endophytic bacterium.It also impacts significantly the phyllosphere actinomyces on the leaf surfaces,but impacts less on fungi.The differences of the quantity and species richness of fungi between healthy and sick leaves are most obvious in summer and autumn.(4)By flat confrontation method,this test has filtered 4 antagonistic bacterium,which have strong antagonistic ability towards camellia gray spot disease,i.e.B.amyloliquefaciens, Bacillus subtilis,Delftia acidovorans and Pseudomonas fluorescens;4 antagonistic actinomyces,i.e.Streptomyces californicus,Streptomyce griseus,Streptomyces mediolani and Streptomyces microflavus,which have widths over 0.5cm against pathogen;3 antagonistic fungi,i.e.Phoma exigua,Botryotinia fuckeliana and Didymella bryoniae,of which Phoma exigua has width of 0.7cm agaist pathogen.The other two fungi restrain the growth of pathogen by nutrition competition,with restraint rate over 50%.(5)The disease index of camellia gray spot disease has negative correlation with the diversity and equality of fungi species in different seasons.In spring and winter,the diversity and equality of fungi species are high;while the disease index is small.In summer and autumn,the diversity and equality of fungi species are small;while the disease index shows quite high.There is some correlation between all dominant microorganism and pathogen Pestalotiopsis guepini.Actinomyces S.mediolani and fungi B.dothidea have negative significant correlation with P.guepini in terms of quantity;while G.camelliae has significant positive correlation with P.guepini at the 0.01 level.