| Summary: | 碩士 === 國立中興大學 === 植物病理學系 === 87 === Taiwan Anoectochilus plants with the basal stem rot symptoms were collected from Yiechu, Nantou and campus of NCHU. Three distinguished isolates of Pythium spp. were isolated. After satisfaction of Kocks postulates, the causal organisms were identified as Pythium myriotylum (Drechsler), P. aphanidermatum(Edson) and P. splendens(＋) (Braun). These pathogens primarily infected the seedlings soon after transplanted from flasks. The main symptoms of the basal stem rot were water-soaked, soft rot and damping-off. Under favorable disease development conditions high temperature and relation humilities, disease progressive rapidly and cottony aerial mycelial of the pathogen covered the infected plants. A total of 14 antagonistic fungi were isolated from the rhizosphere of Taiwan Anoectochilus. These isolates were dual culture against three basal stem rot fungi Pythium spp., respectively on PDA and all 14 isolates had lethal to all three Pythium spp. By spraying conidial suspension on seedling and in cultivating substrate, isolates of Trichoderma spp., AHS-03, AHS-09, AHS-11, AHS-12, and isolates Gliocladium spp., AHS-01, AHS-07, AHS-08 were able to control the disease caused by P. myriotylum. Four isolates, AHS-01, AHS-02, AHS-08, AHS-10, of Gliocladium spp. and isolate AHS-13 of Trichoderma spp., were also effective control P. aphanidermatum and increased the plant stand rate up to 90% as compared with control, plant stand rate 50%. None of the 14 isolates of antagonists could suppress the basal stem rot incited by P. splendens. The efficacy of treatment with phosphorous acid at 1000X(pH 6.0) to control pathogens of basal stem rot was reached up to 90%. Stem rot caused by Fusarium oxysporum occurs in many cultivations and is the major limiting factor for the growth of Taiwan Anoectochilus (Anoectochilus formosanus Hay.). The objective of this study is to evaluate potential antagonists and mycorrhizaes for their effectiveness to control stem rot of Taiwan Anoectochilus. Antagonistic fungus, AHS-06, was propagated in a mixed substrates including tree-fern aerial root fragments, rice hulls, peat moss and oat meal. Prior to planting Taiwan Anoectochilus, former mixed substrates were blended with peat moss again. As a result, it was significantly effective to suppress the diseases of the stem rot. The plant stand rate was 88% after 7 months planting compared with the check, plant stand rate 22%. Mycorrhizae isolated from both cultivated and wild Taiwan Anoectochilus were identified as member of the genera Rhizoctonia spp. R-01 was binucleate isolate, and RC-1, RC-2, R-1m, R-5m, and R-ro were multinuleate isolates. RC-1 belongs to anastomosis groupAG-6. The optimal temperature and pH value for mycorrhizal fungi varied from 20 to 28℃ and pH 7 to 9, except for RC-1(pH 6.0).The mycorrhizaes could penetrate into the roots 48 hours after inoculation on 5-6 months old seedlings and consequently formed mycorrhizaes on roots in 28 days. The inoculation with R-01 and R-1m for 14 days, or with RC-1 for 21 days was capable of reducing the disease incidence of the stem rot 84 days after planting. The inoculation with both isolate R-01 mixed with Streptomyces saraceticus strain 31 and R-ro mixed with AHS-06 reduced the disease severity. Inoculation of binucleate R-01 isolate in the substrate could slow down the occurrence of the stem rot of Taiwan Anoectochilus 84 days after planting.
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