Selection And Identification Of Antagonist Alternaria Alternata And Initial Analysis Of Its Antipathogenic Activity

Pear is one of the three major fruit in China. As one of the three major diseases, pear black spot is a fugal disease caused by Imperfect fungi, subphylum, silk spore outline, hyphomycetales alternaria. So far, the main method to control pear black spot is chemical disinfectant. On account of the fact that chemical disinfectants have problems such as drug resistance and pesticide residue, they are also a threaten to human health and environment. So, screening eco-friendly, broad spectrum antibiotic bacteria of high bio-control activity and preparing effective bio-control bacteria agent as an efficient supplement to chemical control of pear black spot, we can decrease the usage of chemical disinfectant and reduce environmental pollution.We isolated152strains of Alternaria alternata from about100samples which were collected from13provinces of China. They were classified as8main category according to the differences in culture traits, each of them was taken to culture for sporulation. Of all these strains, one strain named FX02which was isolated from Fengxian county Jiangsu province produced more spores, and inoculating on exsomatized leaves indoor may lead to black spot. Thus, we used FX02as the test strain to screen antagonistic bacteria to Alternaria alternata. We isolated613strains from the diseased leaves of Pear black spot which was from Qian County Shanxi Provence, Tangshan Anhui Provence and JuRong JingSu Provence.We obtained an strain that significantly inhibiting the Alternaria alternate using the plate confrontation method. This so called JR-C Strain was isolated and purified from the leaves sample in JuRong JingSu Provence, which has obvious inhibition effect on Alternaria alternata. Based on an aggregate analysis of morphological characteristics, Biolog and16S rDNA, it’s identified as Bacillus subtilis. Extracellular enzyme activity detection showed that the strain can produce protease and cellulase, but no chitinase or β-1,3-glucanase. Furthermore, the metabolite of this bacteria can inhibit the normal growth or germination of pear black spot’s hypha and spore. When the concentration of metabolite come to20%, a92.19%minish in pear black spot colony was obviously observed compared to control colony. If concentration of metabolite of JR-C reached to50%, the inhibition ratio of germination of Alternaria alternata spore can reach up to78.14%. When treated with metabolite of the strain, the hypha of pear black spot fungi changes into tighter, tubbier and with less branches. Otherwise, it’s tested by dual culture that stain JR-C has a wide range of antagonistic spectrum which shows obvious inhibition to the pathogens of common fungal diseases on crops and horticulture plants, but not to Oomycete. Extracted and identificated the lipopeptide compounds of JR-C, and found that the bacteria do not produce the typical lipopeptide compounds.The strain has a higher anti-pathogenic activity and a wide antagonistic spectrum, which could be used as a bio-control technology support to treat pear black spot and other corp diseases. Besides, as a useful addition to chemical pesticides, we can reduce chemical pollution.