Pathogen Identification And Fungicides Screening Indoor On Codonopsis Lanceolata Benth.et Hook. And Dioscorea Nipponica Makino

Five new diseases which are Codonopsis lanceolata Septoria leaf spot, Dioscorea nipponica Rhizoctonia damping-off, Dioscorea nipponica smut, Dioscorea nipponica rust and Dioscorea nipponica bacterial top blight respectively were first reported in Jilin Province in China. The sympotoms of the five diseases were described in detail, and biological characteristics and fungicide-screening indoor on some of pathogens. were studied.The main symptoms of the fungal disease on Codonopsis lanceolata were leaf spots. It initially appeared as a white dot in the center of the spots and the spots were dark geeen than the healthy tissues around. With the disease spread, the white dot gradually turned brown and there were the dark brown to black haloes around the spots. The figure of conidia were like neddle with the top acuate, a few of them were acuate on both sides. The conidia were colourless, a little curving, 23-44×1-5μm with 1-4 transverse septa, most of them had 2-3 transverse septa. According to the symptoms of the disease, morphology and biological characters of the pathogens and comparison with concerned Septoria species, the pathogen was identified as Septoria codondpsidis Ziling.The stalks and leaves which were approach the ground were mainly damaged by the Dioscorea nipponica Rhizoctonia damping- off. It initially begun from the bottom leaves with dark green lesions like water marks. After the lesions became rot, the seedlings fell down and died. The contiguous plants were creeped with white downy mycelium. Finally the mycelium formed brown flinty sclerotiums. The diameter of hypha was 6-12μm, presenting orthogonal branches with obvious shrink. Not far from the branches there were septa and 3-5 nucleolus in the hypha. According to the symptoms of the disease, morphology and biological characters of the pathogens and other concerned, the pathogen was identified as Rhizoctonia solani Kuhn.The main symptoms of Dioscorea nipponica smut was strip spots in the stalk, nervation and leafstalk. The tissues of hosts were embed with telium at the beginning, then the black telium exposed. The stalks and leaves were malformation and the plants were dwarf with leaves light green. Finally the leaves became yellow died. There was usually only one spore in the telispore balls, but occasionally there were two spores in it. The telispore were surrounded by a flat sterile cells. The diameter of spore was 8-15×6-10μm. The sterile cell was snuff colour and the diameter was 4-12μm. According to morphology of the telispore and telispore balls, the pathogen was identified as Urocystis dioscoreae Syd.The main symptoms of Dioscorea nipponica rust was leaf spot. The yellow dots were on the face of the leaves and the ferrugineous or black brown ridgy bracteal lesions were on the backof the leaves. Finally the bracteal lesions exposed and the ferrugineous or black powder were spilled out. The leaves gradually became yellow and dry rot, and damaged the photosynthesis of the leaves seriously. According to the symptoms, the characters of telispores and urediniospores and other concerned, the pathogen was identified as Puccinia dioscoreae Kom.The main symptoms of bacterial top blight on Dioscorea nipponica were necrosis of growing points. The strains were bacilliform, Gram-negative, peritrichous flagella six or more; could infect Dioscorea nipponica; 37℃growth negative; 5%Nacl growth positive; sucrose reduction positive; potato rot positive; malonic salt negative; gelatin liquefaction positive; indole negative; lecithinase negative; erythromycin sensitivity positive; acided from maltose, lactose, trehalose, melibiose, cellobiose, esculin, levulose, D-galactose, D-gluconate, glycerol, sorbitol, D-mannitol, D-mannose, rhamnose, salicin,sorbite, starch, sucrose, D-xylose; couldn't produce acid from melezitose andα-CH3-D-gluconate; According to parts of《Bergey's Manual of Determinative Bacteriology》9th ed, it confirmed that the disease was caused by Erwinia rhapontici (Millard) Burkholder 1948.Codonopsis lanceolata septoria leaf spot, Dioscorea nipponica Rhizoctonia damping-off, Dioscorea nippOnica smut and Dioscorea nipponica bacterial top blight were not reported in the world, so Codonopsis lanceolata and Dioscorea nipponica were new record hosts of their pathogens. Dioscorea nipponica rust was first reported in Jilin Province in China.Fungicides were screeded for two fungical diseases with methods of inhabition zone and growth rate indoor; The lowest effective concentration and the diameter of inhabition zone of eight bactericides to bacterial top blight were tested indoor. The results showed that the inhabtion rate of Topsin M was the highest to Codonopsis lanceolata, the inhabtion rate of Polyoxin et al. to Rhizoctonia solani were all above 90%, so they were the preferred fungicides used for the field trial. Streptomycin sulfate was not only the best effective to inhabit the pathogen, but also the lowest effective concentration to inhabit pathogen, so streptomycin sulfate was the preferred bactericide to Erwinia rhapontici for field trial.