Biocontrol effect of broad-spectrum antagonistic actinomycete on melon gummy stem blight

【Objective】 This paper intends to identify the actinomycete strain C28,and to evaluate its antagonism against 12 plant pathogenic fungi and biocontrol effect on melon gummy stem blight.【Method】 Antagonistic effect of actinomycete strain C28 on the target fungi was determined using agar block method and mycelia inhibition test;Pot trial was conducted to determine the biocontrol effect of C28 against gummy stem blight on melon plants,and strain C28 was identified by way of morphological character,physiological and biochemical characteristics,as well as 16S rDNA sequence analysis.【Result】 ①Actinomycete strain C28 showed obvious antagonistic effect on the tested pathogens,with the diameters of inhibition zones ranged from 10.0-22.5 mm.The axenic culture filtrate of C28 also displayed certain inhibition on the fungal mycelia growth,the inhibition rate of C28 against Fusarium equiseti,F.proliferatum and Botryosphaeria dothidea was 95.0%,90.0% and 93.1%,respectively.②The length of melon hypocotyl and radicle were increased by 37.1% and 12.5%,respectively,and the simple vigor index highly reached 141.7,significantly different from the control(P0.05),when treated with 104 times dilution of C28 culture filtrate.③Strain C28 also showed definite biocontrol effect on melon gummy stem blight,the disease indexes were significantly decreased by 42.4% and 40.0%,respectively,under the protective and curative conditions.④Based on morphology character,physiological and biochemical characteristics,as well as 16S rDNA sequence analysis,strain C28 was identified as Streptomyces globisporus subsp.globisporus.【Conclusion】 Streptomyces globisporus subsp.globisporus C28 showed strong pathogen inhibition and disease biocontrol effect on melon gummy stem blight,as well as promotion effect on melon seeds germination and growth.