Pathogen identification and biocontrol microbes screening of sisal black spot in Guangxi

【Objective】 To isolate and identify the pathogen that caused round, subround or long oval hollow black spots on sisal leaves in Guangxi, and to screen out biocontrol microbes with better control effect on the pathogen, and provide scientific basis for the control of this disease.【Method】 The diseased leaves with round, subround or long oval hollow black spots were collected from 5 farms in Guangxi. The pathogen was isolated by tissue isolation method. The pathogenicity of pathogen was determined by leaf acupuncture inoculation. The pathogen was identified by observing morphological characteristics and molecular biological methods. The inhibitory effects of Trichoderma harzianum GZ-5, T. atroviride ST-1, Bacillus subtilis B11, B. amyloliquefaciens YZ14-3 and their filtrate on mycelial growth and spores germination of the pathogen were studied by plate confrontation culture method and slide spore germination method.【Result】 Six kinds of fungi were isolated from diseased tissues, the isolation rate of strain JMHB1 was the highest(96%). JMHB1 was the pathogenic bacteria according to the pathogenicity test, which was identified as Neoscytalidium dimidiatum based on morphological characteristics and molecular identification. Biocontrol strains B11 and YZ14-3 could significantly inhibit the mycelia growth of JMHB1(P<0.05) according to plate confrontation culture method, the radius of inhibition zone were 12.14 mm and 13.22 mm respectively, and their culture filtrates could lead to constriction and break of JMHB1 mycelia. The antagonistic coefficients of ST-1 and GZ-5 against JMHB1 were Ⅲ and Ⅳ respectively, but their culture filtrates had no inhibition effects on JMHB1 mycelia. Spores of JMHB1 could germinate in the culture filtrates of strains YZ14-3, B11, ST-1, GZ-5, the spore germination rates were 31.67%, 32.37%, 68.63%, and 76.63%, respectively.【Conclusion】 The pathogen that causes round, subround or long oval hollow black spots on sisal leaves in Guangxi is identified as N. dimidiatum(Penz.) Crous & Slipper. This is the first report of sisal black spot caused by N. dimidiatum in China. The disease is temporarily named as Neoscytalidium black spot. B. amyloliquefaciens, B. subtilis, T. atroviride and their commercial preparations can be selected and used to control Neoscytalidium black spot disease in sisal production.