Pathogen Analysis, Symptom Expression And Fungicide Screening Against Pathogen Of Jujube Black Spot Disease

To definite the symptom expression of jujuba black patch and taxonomic position of pathogen fromthe tissue of leaves, flowers, fruit and to control the disease, the symptoms of jujube black spot wereobserved and recorded, the pathogen were isolated from different tissue and the pathogenicity wasdetermined. Combined with rDNA-ITS sequence and β-tubuLin sequence analysis, the pathogen wereidentificated by morphological observation. The results showed that the leaves, flowers and fruits wereinfected by Alternaria spp., the symptom expression of field observation was the same as indoor, and thepathogen could infect from the jujube leaves, flowers and fruits each other, the typical symptoms of jujubefruits were showed.357isolates were obtained from different tissue. The strains from the infected leaves,flowers and fruits were identified as A.alternata by the morphology.3strains were selected as molecularidentification by PCR amplification using the fungi rDNA-ITS universal primers (ITS1and ITS2) andβ-tubuLin primers and sequence analysis. The pathogens from leaves, flowers and fruits were identificatedas Alternaria alternate by morphological observation and molecular sequence analysis. The inhibitoryeffects of7fungicides on red jujube Alternaria alternate were determined by growth rate and concave slidemethod.The results showed that conidia germination and mycelia growth were inhibited by all fungicidestested except Thiodiazole-copper. The mycelial growth inhibition of Imazalil was the highest,Pyraclostrobin, Difenoconazole and Silicon of carbendazim took second place. Triazole ether metiram,Mancozeb and Imazalil were high on the inhibitory effect of spore germination compared with the otherfungicides. Through Fruits-inoculation test in vivo, the protective and curative effects were measuredagainst Alternaria alternate. Results indicated that Triazole ether metiram and Mancozeb showed strongprotective activity and the other4species fungicide, except Thiodiazole-copper, showed strong curativeeffect which of the outstanding were Imazalil, the following were Pyraclostrobin, Difenoconazole, Siliconof carbendazim. Microscopic observations showed that the agents with obvious inhibition to hypha couldcause mycelium abnormal morphology, include mycelium swollen, more shorter branches, hyphal wallcollapse, plasma concentration and extravasation, and the agents with obviously inhibition to germinationof spores could led to spore swelling, deformation or rupture.