Studies on control of tomato bacterial wilt by endophytic antagonistic bacteria from tomato

• Main Authors: Chen, Mei-huei, 陳美惠
• Other Authors: S.T.Hsu
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/64399761753765439257

碩士 === 國立中興大學 === 植物病理學系 === 84 === A total of 227 bacterial strains antagonistic to Pseudomonas solanacearum on media were isolated from interior tissues of stems of healthy tomato plants ( 208 strains ) and other sources (welsh onion rhizospheres , tobacco plants ). They were tested for the ability to control tomato bacteria wilt after introducing into plants by the Kijima,s hypocotyl-cuttings method in a screenhouse. Only nine strains can reduce the disease severity significantly. Among the nine strains, strains K8-1、EA2-4、KA4-1 and A10-5 were more consistent in their control efficacy during repeated testing. These four strains were all isolated internaly from the stem of healthy tomato plants, and were termed endophytic antagonistic bacteria in this study. Strain KA8-1 was identified as Bacillus sp., strains KA4-1 and A10-5 as Pseudomonas spp. , but strain EA2-4 could not be identified based on the Biolog identification system. Factors affecting the biocontrol efficacy of the four strains of endophytic antagonistic bacteria by the hypocotyl-cutting method were studied in the greenhouse. The influence of each factor on the control efficacy varied among tested antagonistic bacteria. The antagonistic bacteria were more effective when using 10 and 13-day old seedlings for hypocotyl-cutting treatment than seedlings at the other ages. When soaking period during the hypocotyl-cuttings treatment was too long or short, it was not suitable for all or some strains of the antagonistic bacteria ; the best soaking period was 12 hr. Except strain EA2-4, allstrains showed biocontrol efficacy on susceptible and resistant varieties ( lines ) of tomato. The best concentration of the antagonistic bacteria used for dipping was 108 cfu/ml . Control efficacy of the antagonistic bacteria varied when the disease was caused by different strains of P. solanacearum. The control efficacy of antagonistic bacteria was more easily demonstrable in the soil infested with P. solanacearum at the density of 107 or 106 cfu/g dry soil. Biocontrol efficacy of the antagonistic bacteriawas affected by temperature ; Except strain EA2-4, the best control efficacy was obtained at 30℃. Among different treatment methods of antagonistic bacteria , the hypocotyl-cutting and seed bacterization methods resulted the best control efficacy by all or most strains of the antagonistic bacteria. The antagonistic bacteria existed in stems and roots after introducing into tomato plants by the hypocotyl-cutting method. The populations of antagonistic bacteria declined more slowly in roots than in stems with the time during the growth of tomato. Fourty-two days after introduced into plants, populations of all antagonistic strains in roots and stems remained as 104-106 cfu/g fresh root and 103-105 cfu/g fresh stem, respectively. The population of K8-1 was the highest detected in the plant, which were 1.17×106 cfu/g fresh root and 2.90×105 cfu/g fresh stem, respectively; the population of EA2-4 was the lowest, which were 1.80×104 cfu/g fresh root and 1.35×103 cfu/g fresh stem, respectively.When the antagonistic bacteria and P. solanacearum were present together in the tomato plants, the population dynamics of the antagonistic bacteria in roots and stems were similar to those described above, whereas the populations of P. solanacearum increased with the time. Even though the population of P. solanacearum did not seem to be declined, the disease severities of the plants treated with all antagonistic bacteria were significantly lower than control plants.