Study On Classification And Phage Of The Pathogenic Bacterium And Occurrence Of Kivifruit Bacterial Canker

Bacterial canker of Kivifruit is destructive and hard to control disease. It caused severe economic loss. The objectives of the study were to identify the bacterial subspecies; to isolate the phage of the pathogen; to observe the disease occurrence and development in field condition; to screen for chemical agents and isolate the bacterial antagonist against the pathogen. The studies provide trustworthy base for preventing and curing the disease. The results are as follows:1. Isolation and identification of the pathogenic bacteria The pathogenic bacteria were isolated from plants infected bacterial canker of Kivifruit which were collected from Kivifruit orchard in Cangxi, Sichuan province, DujiangYan,Sichuan province and Chongqing. Pathogenic bacteria was identified as Pseudomonas syringae pv.actinidiae by the tests on the pathogenicity and biochemical characters.2. Occurrence of the bacterial canker of Kivifruit Occurrence of the disease was invested in Kivifruit orchard in Cangxi, Sichuan province. The pathogen of infected tissue was source of primary infection and secondary infection. Wounds were the main invading way. There are two periods of the disease occurrence and development in a year. The first one is from sprouting to blossom dropping in spring, the second one is before or after fruit ripening in autumn. The disease incidence was higher above 600 meters altitude and among older trees. More plants were infected in sunny side slope than in poor light slope. The occurrence degree of the disease was different with variaties, "Hongyang" was susceptibility and "Haiwote" was resistance.3. Isolation of the bacteriophage and its biological characteristics A bacteriophage of Pseudomonas syringae pv. actinidiae was isolated from plants infected bacterial canker of Kivifruit. Its morphology and biological characteristics were analyzed. Results showed that the phage appeared like a tadpole by electron microscopy observation, it had an isometric head(about 70 nm in diameter) and a long tail(about 90 ran in length), its Nucleic acid was DNA, its hot-stability was weak, 65℃heating for 10 min could inactivate them completely, they had relatively high stability at pH4～9, they were deactivated after exposure to ultraviolate for 12 min, the optimal multiplicity of infection of the phage was 0.1, One-step growth curve of the phage showed that the latent period and the burst period were about 60 min and 70 min, the average burst size was about 123 phage particles per infected bacterium. It is the first time to study and report the phage of Pseudomonas syringae pv. actinidiae.4. Screening for chemical agents against the pathogen Using disc diffusion method and streak plate method, the antibacterial activity of twelve chemical agents were tested. The result showed that Lu heng 6 hao, Nong yong liu suan lian mei su, Kangfa, Mi hou tao kui yang bing jue were very effective to the pathogenic.5. Isolation and screening for antagonistic Bacillus spp 305 strains of Bacillus spp. were isolated from the soil of the rhizosphere of Kivifruit. Fifteen antagonistic strains of Bacillus spp. which inhibit the pathogen of bacterial canker of Kivifruit were obtained. The diameter of inhibition zone of six strains was lager than 10 millimeter. Especially, BT4 and BT9 were obvious. They are favourable potential biocontrol strains.