| Summary: | 碩士 === 國立嘉義大學 === 生物資源學系研究所 === 101 === Abstract
The Phytophthorablight of ribbon grass (Spiranthes sinensis) was found in the orchid garden of Hualien area, Oct.2010. The stems and leaves at the base with water-soaked, black spots gradually expanded. Finally, the leaves had decayed, and the whole plant had withered and died. By spraying zoospores at the base and leaves of ribbon grass for inoculation to increase the symptoms is infective. The aim of this study was to indentify the pathogen involved. Phytophthora blight caused by Phytophthora nicotianae is a new disease of ribbon grass. In this study, diseased plants were collected and the pathogen strains were isolated by the external morphology and ITS rDNA, and the pathogen was identifiedP. nicotianae (Breda de Haan). The fungi in 10 % vegetable juice agar medium (10 % V8) grew rapidly and it was often tufted mycelial growth, conspicuously papillate, broadly ovoid, obpyriform to obturbinate, non-deciduous sporangia. The colony appeared white. The concentration of zoospores was from 104 to 106spores/ml, and the disease severity was from 70%to 80%. The optimum growth temperature of mycelial gorwth was30 ℃,with a suitable temperature range between 25℃and 35℃. The optimum growth temperature of zoosporangia was 30 ℃ with a suitable range between 25℃and 35℃. Max number of zoosporangia was three days. Eleven carbon sources and fourteen nitrogen sources were chosen as nutrients for investigating their effects on the mycelial growth and sporulation. A comparison of different carbon sources showed that soluble starch promoted the best mycelial growth, while malt dioxide sugar gave the least growth. A comparison of different nitrogen sources showed that peptone (bacto peptone) promoted the best mycelial growth, while proline gave the least growth. Weretest ; andeleven kinds of different media on the mycelia growth and sporulation, the fastest growing mycelium was shown on 10% and 20%V8, and the largest sporulation was found on 10% V8.The pharmaceutical petri dish test is that 10% V8 petri dish was added different concentration of pharmaceutical. The abilitieson inhibition of mycelial growth were examined, and ten commercial agricultural concentration, amongthem Chlorothalonil(75% WP)、Kasuran(81.3% WP) and NPA(30% Neutralized Phosphorous Acid solution) had inhibition respectively. There was a good inhibitory effect by the three, and the IC50 were 0.04、0.5、0.8 ug/ml respectively.Kasuran 500 X and NPA 500 X showed significant effect on the control of P. nicotianae on ribbon grass. The disese severity was below 25 %, and the control was 76 %. We sprayed agricultural concentration one time per seven days, totally four times. Ten kinds of antibacterial were paired culture, actinomycetes Apt1-1、Apt1-2 and isolated in the laboratory 20111103Y、20111103W on PDA,the zoon of suppression ring were 2.75, 2, 2.5, 3cm. 20111103Y、20111103W on 10% V8,the zoon of suppression ring were 1.75, 2cm. Four antagonistshad a significant inhibitory effect on mycelia growth. However, the antagonists for the control of P. nicotianeon ribbon grass were not effect. We selected seven kinds of herbals extract from seventeen kinds of herbals to inhibit spore germination. Rhubarb, dictamni, scutellaria, magnolia, Chinese gall, Chisandra and cassia can inhibit spore germination below 10%.Seven kinds of herbals dilution 60 X and vitality dilution 500X showed significant effect on the control of P. nicotianae on ribbon grass. The best control effect, scutellaria was 27 %, then cassia was 34 %,rhubarb was 39%, vitality was 39 %,dictamni was 41%,Chinese gall was 42%, and the control was 78 %. We sprayed diluent one time per five days, totally four times.
Key words：ribbon grass ,Spiranthes sinensis ,Phytophthora nicotianae, disease control
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