| Summary: | 碩士 === 國立中興大學 === 植物病理學系所 === 103 === The objectives of this study were to A) analyze the diversity of endophytic fungi in Cirsium kawakamii Hayata, a herb indigenous in Taiwan, B) observe the effect of geographical and seasonal factors on endophytic fungi, C) screen the potential biocontrol agents of endophytic fungi in controlling the Fusarium wilt of lettuce and D) evaluate the risk of endophytic fungi as potential plant pathogens. In this study, a total 1836 endophytic fungi isolates were isolated from C. kawakamii plants collected from Puli Township, Tatachia, and Hehuanjian area. All these isolates were classified into 2 phylum, 8 classes, 40 families, 68 genera, and Colletotrichum, Xylaria, and Fusarium were the dominant genera, which belong to Sordariomycetes, Ascomycota. The EstimateS software was also used in this study to evaluate the diversity and richness of endophytic fungi in C. kawakamii. The Fisher’s α and Shannon diversity indices were 13.95 and 2.66 respectively, and the richness indices of Chao 1, Chao 2, First-order Jackknife richness, Second-order Jackknife richness, and bootstrap value were between 76.00 to 96.99. Moreover, the genera accumulation curve remains non-asymptotic according to the bootstrape estimator, and the estimated richness significantly exceeds the richness captured by our sampling to date. Therefore, the endophytic fungi in C. kawakamii are highly diversity and richness, in addition, the diversity and richness of endophytic fungi showed the highest indices in Tatachia than the other two places, and the diversity of endophytic fungi in summer was higher than in winter at Puli Township area. The similarity indices of endophytic fungi showed the highest value between Puli Township and Tatachia. To evaluate the effect of geographical and seasonal factors on diversity and richness indices of endophytic fungi, the result indicated that the season was the key factor. The bioactive test showed that 174 of 1145 isolates showed antifungal ability against the mycelial growth of Fusarium oxysporum f. sp. lactucae race 3 Fo-10. Among these isolates, the Fusarium sp. was chosen for future study. The isolate CKK6059 showed the best inhibition ability in plate assay. Therefore, the isolate CKK6059 was used as a biocontrol agent in controlling Fusarium wilt of lettuce in greenhouse experiment. The result showed that the isolate CKK6059 could delay the disease progressing and decrease the disease severity with 18.4% at 28 days after inoculated into lettuce plants by root-dipping method. Moreover, the isolate CKK6059 showed the ability in promoting the plant growth in C. kawakamii, but with negative result in lettuce. In the risk assessment, the isolate CKK6059 and the isolates of Neofabraea spp. were chosen to evaluate the pathogenicity on crops. The results of pathogenicity test indicated that the CKK6059 could cause potato dry rot, apple fruit rot, and Fusarium head blight on wheat. Furthermore, the susceptibility of different apple cultivars from high to low was Granny Smith, Fuji, Red delicious, and Gala, respectively. The phylogeny analysis result indicated that the endophytic fungi of Fusarium sp, in C. kawakamii were divided into several groups and might belong to different species. On the other hand, the isolates of Neofabraea spp, could be separated into three groups based on the morphology and the phylogeny analysis results of ITS region. In preliminary test, the isolate CKK2013 (groupⅠ) was proved with the pathogenicity and caused the bull’s rot disease on apple and pear. In addition, each two isolates form these three phylogeny groups were chosen randomly and for evaluating their virulence on Granny Smith apple. The results indicated that the groupⅠhad the highest virulence and groupⅡwas the lowest virulence on apple.
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