Identification for Physiological races of Fusarium oxysporum f. sp. lactucae and Control Experimentsof Lettuce Fusarium WiltIdentification for Physiological races of Fusarium oxysporum f. sp. lactucae and Control Experimentsof Lettuce Fusarium WiltI

• Main Authors: Ju-Ling Huang, 黃久菱
• Other Authors: Jenn-Wen Huang
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/77586324784868253600

碩士 === 國立中興大學 === 植物病理學系 === 93 === In Taiwan, lettuce Fusarium wilt caused by Fusarium oxysporum f. sp. lactucae is a serious soil-borne disease in monoculture fields during summer season. The disease plants of lettuce appeared yellowing, vascular discoloration of taproots and stems, stunning and wilt symptoms. The disease is one of the limiting factors of yield in commercial lettuce cultivation. Three lettuce cultivars, Costa Rica No.4, Benchu Red Fire and Patriot were used as differential cultivars for identification of the physiological races of F. oxysporum f. sp. lactucae. The results indicated that 12 isolates of the pathogen obtained from Taiwan were identified as race1, howeven the pathogenical characteristics of three isolates LFO 32-14, LFO 106-1 and LFO 106-3 were different from ones of three races of Japanese and USA isolates. The results suggest that a new race of F. oxysporum f. sp. lactucae may has occurred in Taiwan. Susceptibility of thirty lettuce cultivars to isolates LFO 11-13 and LFO 32-14 was apparently varied degree. Among the cultivars tested, asparagus lettuce and crisp head lettuce were the most resistant to Fusarium wilt. However round-leaf lettuce, pointed leaf lettuce and indian lettuce were very susceptible. In this study, amendment of soil with crab and shrimp shell powder, soybean meal and CH100-S was able to enhance lettuce growth and reduce disease severity of lettuce Fusarium wilt. CH100-S, a new formulation of Plant health guard CH100 paste, was obtained from precipitate substance of a mixture solution for producing CH100 that includes major ingredients of S-H mixture, extracts of tobacco and cabbage, and is recommended for control of a wide range of plant pests. Application of CH100-S at 1000-fold dilution was significantly effective in reducing disease severity of lettuce Fusarium wilt in greenhouse test. Lettuce seeds were sown in infested soil which had been treated with CH100-S for six days. The disease severity of lettuce Fusarium wilt was markedly reduced 27 – 50 %. CH100-S did also promote growth of lettuce plants and stimulate proliferation of beneficial microorganisms including fungi, bacteria and actinomycetes. Beneficial microorganisms were isolated from the CH100-S-treated rhizosphere soils, and showed either antagonistic ability to the pathogen or promoting plant growth. These bacterial isolates including B122, CHB139, CHB143, CHB180, CHB184, CHB186 and CHB190 were significantly effective in reducing disease severity and increasing root weight of lettuce. Especially, amendment of LFO 11-13-infested soil with CH100-S mixed with CHB184 was more effective than CH100-S alone in reducing disease severity.