| Avirulent strains of Ralstonia solanacearum (ATm044 and Asp061)were obtained by UV-ray mutation. Their pathogenicity, colonizing ability, activities of induced resistance were observed. Physiology and biochemistry characters in induced tomato leaves were measured. Inhibitory activities of crude extracts to Ralstonia solanacearum were also tested. Meanwhile, induced resistance of tomato to Ralstonia solanacearum was also tested in greenhouse and field. The results were as follows:The 2 avirulent strains of Ralstonia solanacearum were obtained by UV-ray mutation based on the assessment of the period of disease development delayed, the incidence of disease and disease index after treatment. The resistance induced by avirulent strains in tomato were measured and the result showed that the mean period of disease appearance was delayed 9.3d and 7. 7d respectively. The incidence of disease were 57.8% and 66. 7%, and the effects of treatment after 20d were 59. 1% and 53.6% respectively.The pathogenicity of 2 avirulent strains were measured in vivo as well as in vitro by stem-injecting and root-wounding. The results showed that 2 avirulent strains can not be pathogenic to tomato again, but inoculated with the virulent strains Tm04 , the tomato was wilt. Colonizing ability of avirulent strain in stem and roots of tomato was investigated, it was found that the avirulent, strains, ATm044 and Asp061, could be colonized in tomato.Physiological and biochemical characters of tomato leaveswere measured after inoculation with ATm044.The results showed that the activities of peroxidase (POD), phenylanine ammonia lyase(PAL) and polyphenoloxidase ( PPO) in tomato leaves were increased in varying degree. The contents of phenolic compounds and lignin were higher than the contrast plant. Pathogenesis-related protein(PRP) was also increased in content.The crude extracts were extracted from the tomato leaves, and inhibitory activities of crude extracts to Ralstonia solanacearum were also tested in vivo and in vitro, the results showed that the crude extracts from tomato leaves inoculated with ATm044 and AspOGl showed a very strong inhibitory effect on virulent strains in vivo as well as in vitro.Induced resistance to Ralstonia solanacearum in tomato were reported and 4 induced methods: pin-prick, root-soaking, soil-drenching and spraying were used. The results showed: the effects were influenced by different induced methods. The effects of pin-prick and root-soaking were better than the others, the effects were 49.7% and 52.6% respectively, but no control effect was given by spraying. The results showed that the disease development were delayed 9d and 7d respectively after treated with ATm044 and Asp061 in greenhouse. The incidence of disease were 43.3%-61. 7% and 46. 6%-67. 8% respectively, the control effects were 56. 7% and 53.4% in greenhouse. |
