Screening, Identification And Antagonism Of Antifungal Strains

Fungal disease is one of the main reasons for crop production losses,as 80% of plant diease is caused by plant pathogenic fungi. The chemical pesticide abuse for decades has led to serious problems in food and environmental safety and drawn much concern all over the world. And that's why people are looking for pollution-free methods to control plant disease.In this research,we isolated microbes from rhizosphere of different trees',which strongly antagonistic against plant pathogens.We isolated 406 actinomycetes strains from 30 soil samples,which were collected from the rhizosphere of different trees'in experimental station. Screening of 20 strains in plate showed that 2 strains were strongly antagonistic against Fusarium graminearum,Pyricularia grisea and Dothiorella gregaria. And the A7 strain is much more active with a wider bacteriostat spectrum.At the same time, a kind of antagonism bacteria was discovered by accident and found to be a single strain, therefore, we named it as LXH-B-1.The research showed that it was strongly antagonistic against Fusarium graminearum , Pyricularia grisea, Dothiorella gregaria, Botrytis cinerea and Venturia nashicola with all the bacteriostatic spectrum over 9 mm by flat confrontation method. And their fermentation liquor's inhibition ratio to these pathogenic bacteria are 71.73 %,57.14%,69.36% and 73.58%, respectively;The reasonable dilution factor of fermentation can increase tomoto seed germination and promote the root growth; apple leaves soaked by 1X and 100X of the fermentation liquor could prevent being infected by Dothiorella gregaria;Cell subculture showed that its antagonistic activity was very stable and resisted to ultraviolet irradiation.The strain was characteried based on its phenotypic and genotypic.It was a rod-shaped,endospore-forming,gram-positive bacterium.Phylogenetic analyses using 16S rRNA gene sequences showed that LXH-B-1 strain was affiliated to the genus paenibacillus;and was closely related to Paenibacillus peoriae DSM8320,with 99.7% sequence similarity.Meanwhile it had different colonies morphological characteristics in PDA and LB medium,use all sorts of sugar to produce acid and gas,hydrolysised starch and so on. Some research on antagonism also been done, and we found that the active production of LXH-B-1 strain had a strongly inhibition of the mycelia growth and spore germination which led to the mycelia twisted and inflated ,the abnormal branchng increased and so on. KEY WORDS:fungal disease;antagonistic strain;identification;antagonism...