Identification Of Pathogenic Bacteria Of Chinese Cabbage Leaf Spot And Resistant Identification

The bacterial leaf spot of Chinese cabbage is a kind of diseases on leaf at the end stage of vegetative reproduction,severely leading leaves of Chinese cabbage cracked and withered,which was a negative factor for the quality and yields of Chinese cabbage.And the disease has outbreaked more and more frequently and seriously in recent years.On the side reseaches of this bacterial leaf spot diseases were limited and even ignored by researchers in past all over the world.We put on our experiments to identify the pathogenic bacteria of Chinese cabbage bacterial leaf spot in Harbin,Heilongjiang province,China by conventional and molecular methods,including the host range of leaf spot,the physiology and biochemistry characters of diseases and the methods of resistance identification.All the brief results were listed as below:1.We obtained five pathogenic bacteria strains by separation from infected leaves of Chinese cabbage in Harbin.And these were identified as Pseudomonadaceae byobvation of single bacterial colony shape,gram staining and flagella staining.2.These five pathogenic bacteria were amplified 16 s rDNA and blasted on the NCBI database,which indicted that No.1belonged to Pseudomonas putida,No.2,4,5 strains belongs to Pseudomonas viridiflava;No.3 strain belongs to Pseudomonas syringae.And the GenBank accession number of No.2 strain was MG686550.3.The host range of Pseudomonas viridiflava was identified,which were extensive range including legumes,melon,solanaceae,gramineae,and liliaceae.Back-to-back identification showed that the pathological conditions of plants inoculated with Pseudomonas viridiflava were basically the same as those in the field.4.Physiological and biochemical identifications of Pseudomonas viridiflava foundthat:(1)The optimum temperature is 22°C,and high temperature limit is 53°C.(2)The salt-tolerance were identitied by 3% and 5% NaCl.Stains showed little suppression treated with 3% NaCl,however the inhibition of 5% were significant,which revealed the salt tolerace of Pseudomonas viridiflava was low.(3)Results showed that strain was a kind of aerobicanaerobic bacterias,and the growth was weaker under anaerobic condition.(4)Pseudomonas viridiflava could obtain carbon from malonite and citrateinstead ofnitrate as nitrogen source.(5)The experimental hydrogen peroxide reaction is positive withacid production,instead of gas;gelatin were liquefied by Pseudomonas viridiflava;generation of hydrogen sulfide;thehydrogen peroxide Methyl red assay was negative withyellow appearace of;V_P assay waspositive.5.The resistance identification methods of Chinese cabbage Pseudomonas viridiflava were built,which showed that spraying on the leaves of Chinese cabbage at the stage of five/six leaves showed easier to outburst with remarkable symptoms at 15°C/10°C,humidity 90-100%.