Study On The Biology Characteristic Of Garlic Violet Leaf Spot And Culture Conditions Of The Phytotoxin

In the last few years, people already established a selection method which used pathogenicity toxin or toxin analogue linking tissue culture to select resistant mutant in vitro both here and abroad.The aim of experimentation was to study the biology characteristic of the Garlic Violet Leaf Spot and the condition of phytotoxin-producity. Then we could use phytotoxin to select cell variant mutant lines of resistant Garlic Violet Leaf Spot which had steady transmissibility.In the experiment, the pathogen was isolated from pathogenic and typical spots of garlic leaves in the field. The morphologic and pathogenic identification of the pathogen showed that conidiophores were straight or little curved, brown. The conidia usually growed in the shape of single or cluster, clavate or ovate, 5～15 transverse and 1～6 longitudinal septa. Their beaks were straight or curved, 0～7 septa. In view of the morphology and comparison with other concerned Alternaria species, the pathogens were identified as Alternaria porri (Elliott) Cif.The test of biology showed that the growth speed of the pathogen was the fastest and the number of sporulation was also the largest on Potato Shallot Sucrose Agar Medium in five kinds of culture mediums (Carrot Shallot Sucrose Agar Medium, Potato Glucose Agar Medium, Potato Carrot Sucrose Agar Medium, Potato Shallot Sucrose Agar Medium , Carrot Sucrose Agar Medium). The suitable temperature for mycelium growth was in the range of 22～30℃,and for spore production was in the range of 20～26℃. It was not suitable for mycelium growth under 18℃or over 37℃. The optimum temperature for mycelium growth culture was 26℃and for spore production culture was 22℃.The mycelium growth speed was the fastest under the alternate condition of light and dark. But under the continual dark, the number of sporulation was the largest. It could grow and sporulate between pH 5 and pH 12. And the number of sporulation was the largest on pH 8.Aimed at the toxin which be needed in garlic somatic resistance disease variance screening breeding, the condition of phytotoxin-producity capability was studied in the experiment. The result showed that Improved Fries liquid medium was the best for producing phytotoxin in four kinds of phytotoxin-producity culture mediums (Improved-Fries Medium,PSK Medium,Czapek-Dox Medium,Improved-Richard Medium) which be tested in the experimentation. The optimal conditions for producing phytotoxin were temperature 26℃, PH 7, cultured period 7d, continual 24 h dark and shaking. Shallot seed germination was selected to test the toxicity of crude toxin. The result showed that the crude toxin which be cultured had definite toxicity.