Effects Of Deicing Salt And Other Environmental Factors On Gingko Leaf Spot

Gingko biloba L.(gingko) is the oldest relict plant of the extant seed plants, it is peculiar and precious in our country, and it is a common tree species for ornamentation and afforestation in urban landscape with a high timber-used, edible, medicinal and ornamental value. In recent years, serious leaf spot of ginkgo tree occurrs in Dalian. It can cause the leaves of trees to fall ahead of time. In severe cases, the whole plants may wither and die. Therefore, it is imminent to find out a way to prevent the spreading of the disease. we used several methods to identify the gingko leaf spot pathogens; We detected the effect of temperature, humidity, light, p H value, nutritional and other environmental factors to the pathogen, and the antibacterial effect of farm chemicals, antagonistic bacteria and deicing salt on pathogens; Lastly, We analyzed the effect of deicing salt treated on gingko seedlings and pathogens.(1) The dentification of ginkgo leaf spot pathogens: we used several methods such as isolation pathogens from the leaf spot sample, measuring pathogenicity, morphological and molecular biological evaluation, etc. The results showed that two kinds of pathogens lead to gingko leaf spot in Dalian. They were Alternaria tenuissima and Alternaria alternate separately. But so far, Alternaria alternata leading to Gingko leaf spot is rarely reported.(2) The effect of environmental factors on gingko leaf spot pathogens: 25 was found to ℃be the optimum growth temperature of pathogenic bacteria Y3(Alternaria tenuissima) and Y5(Alternaria alternate). The lethal temperatures of the spores were 64 and 6℃ 1 respectively; ℃The optimum p H was 7; When the optimum humidity was 100%, dark environment was suitable for mycelial growth and spore germination. For Y3, the best carbon source and best nitrogen source for mycelial growth were glucose and potassium nitrate. While for Y5, they were sucrose and peptone. The germination rates were the highest in the 2% juice of ginkgo. They were 89.9% and 85.8% respectively. The length of tube and hyphal were respectively 275μm and 269μm.(3) Antibacterial effect of farm chemicals, antagonistic bacteria and deicing salt on pathogens of gingko biloba: Four kinds of antagonistic bacteria and five kinds of farm chemicals were tested for the antibacterial activity of the two kinds of pathogen fungi by colony inhibition method in this paper. The experimental results showed that the inhibition rate of 300g/L Benzoyl propiconazole to the two kinds of pathogenic fungi was 75.79% and 80.11%, respectively; Bacillus circulans had obvious bacteriostatic effect on Alternaria tenuissima, its inhibition rate was high to 80.88%. Both of the two pathogenic bacteria could grow on the medium with deicing salt(the concentration was between 5% and 15%). Therefore, when the deicing salt was used normally(The concentration of the deicing salt used on the street is 2%-8% in winter.), the deicing salt was useless for the pathogenic bacteria.(4) The effects of deicing salt treated on gingko seedlings and pathogens: After treating with deicing salt R1(primary Na Cl) and R2(primary Ca Cl2), the balance of the cellular metabolism in gingko seedlings was destroyed. The physiological stresses were caused, such as physiological drought and single ion poisoning. It is caused that chlorophyll content was reduced. The contents of soluble protein and Malondialde hyde(MDA) were increased. Compared with R2, the effect of R1 was more obvious. And the higher concentration, the more obvious the effect of physiological stress it had. There was a greater impact of the deicing salt on the diffusion rate of gingko lesion. The higher concentration, the faster diffusion rate it had. Deicing salt made the leaf spot more heavliy.