| Summary: | 碩士 === 國立中興大學 === 植物病理學系所 === 99 === Abstract
Endophytic fungi residing in live in medical plants; can produce many kinds of the secondary metabolites. Many reports indicated that many of them could inhibit the growth of pathogens and tumor cells. A total of 197 endophytic fungi isolates from 21 family 32 genus 49 species of the different parts of the medical plants were collected from Fushan, Shinshe and Chitou. We classified as 42 genera base on morphological characteristics and molecular analysis. Among the endophytic flora, Phomopsis、Phomatospora、Guignardia、Nigrospora、Xylaria and Hypoxylon were the dominant fungal endophytes in Taiwan. For Molecular analysis, rDNA sequence of ITS and LSU D1/D2 region were used to evaluate phylogenetic relationship between Xylariaceae isolates by neighbor-joining method (NJ). Results indicated that 33 Xylariaceae isolates could be divided into two major molecular groups, including Hypoxylon and Xylaria. Hypoxylon isolates form a phylogenetic group and support with high bootstrap values (>90%). Xylaria isolates were scattered into different phylogeny clades, they had higher diversity than Hypoxylon isolates in ITS and LSU D1/D2 region. Six isolates was evaluated for its ability to inhibit mycelial growth of plant pathogenic fungi. On the antagonistic activity test, there were six isolates showed antagonistic activity. According to inhibition spectrum, Apoharknessia sp.(CB10) , Stictis. radiata (TR09) and Ophioceras tenuisporum (CI02) showed maximum in vitro inhibition of mycelial growth of plant pathogenic fungi and cell growth of plant pathogenic bacteria. This study selected isolate CB10 for further study because of the higher growth rate. After investigating the impact of temperature, PH and inoculum density in liquid culture, the result reveal that the optimum conditions for bioactivity was added 106 spore/ml cultured in pH 6 PDB medium at 30 ℃, and the best antagonistic activity wound be detect after 18 days. A preliminary test on the disease control of Rhizoctoniasolani AG4 and Colletotrichum higginisianum in greenhouse indicated that the infection was reduced by soaking and spraying application of the mycelial extraction. The application of spray 100 μg/ml mycelial extraction 4 days before inoculum pathogen reduce more disease index percentage of anthracnose infection than 0 dpi before inoculum. The seed soaking 10 μg/ml mycelial extraction is much effective than 100 μg/ml mycelial extraction on controlling damping-off disease. The result may indicated that mycelial extraction can induce resistant of plant.
After analysis of bioactive compounds of mycelium extraction, a flavonoid compound, diosmin, had bioactivity to inhibit pathogenic mycelial growth and induce
Plant resistance. It may develop bioagent used in plant protection.
Key words：endophytic fungi, bioactiveity, secondary metabolite compounds, biocontrol.
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