| Summary: | 碩士 === 國立中興大學 === 植物病理學系所 === 103 === Endophytic fungi inhabiting healthy plants can produce some phytochemicals with the same characteristic of their hosts. Some endophytic fungi that can produce volatile organic compounds（VOCs）are called volatile-producing endophytic fungi. In this study, seven volatile-producing endophytic fungi were obtained from the leaf of Peperomia dindygulensis, among all endophytic fungi, the bioactivity of Nodulisporium sp. PDL-005 was best. VOCs produced by 3-day-old PDL-005 isolate cultured on PSA could inhibit several postharvest fungal pathogens mycelial growth, for example, it can completely inhibit several fungal pathogens such as Botrytis cinerea, while to Penicillium digitatum, the ratio of inhibition is from 88.2% to 99.4%. The efficacy of controlling P. digitatum was obvious but varied a lot. For screening the nutrients to stabilize antifungal ability, the PDL-005 isolate was cultured on the Czapek’s medium which different carbon or nitrogen sources were added to. The results indicated that the single carbon or nitrogen source could not enhance the ability against tested postharvest pathogens. However, the activity of PDL-005 isolate could be enhanced while it was cultured on potato dextrose agar（PDA）、malt extract agar（MEA）and oat meal dextrose agar（OMDA）.Among all medium, the inhibition effect of PDL-005 isolate cultured on MEA was the best（100%）with a killing effect. The nine substrates, including sesame meal, tea seed pomace, soybean meal, wheat grain, wheat bran, oatmeal, rice bran, rice hulls and bagasse were tested in efficiency of enhancing mycelial growth of PDL-005 and the inhibition of P. digitatum. The result showed that the biomass of PDL-005 cultured on bagasse was low, while the inhibition effect against P. digitatum was the best（90.6-100.0%）and had a killing effect. Furthermore, the biomass of PDL-005 cultured on wheat bran was no difference against the highest biomass group-sesame meal and the inhibition rate of PDL-005 isolate against P. digitatum was the second highest（about 86.4%）among all substances. In order to enhance the biomass of PDL-005 cultured on bagasse, the effect was examed that bagasse was mixed with wheat bran in the ratio of 1:3, 1:6 and 1:9 on biomass and inhibition ability of PDL-005 against P. digitatum was examed. The result showed that the biomass of PDL-005 increased more in substrate containing higher proportion of wheat bran, but the inhibition rate of PDL-005 isolate against P. digitatum gradually decreased and lost the killing effect. Next, the PDL-005 grain was made from PDL-005 isolate cultured on bagasse under the process of dried-and-grinded. Furthermore, the PDL-005 grain was mixed with bagasse in the ratio of 2:3 and put into a medicine bag as the PDL-005 product. After rehydration of PDL-005 product for one day, the control value of PDL-005 product against postharvest diseases was examed. The result showed that the control value of 20 g PDL-005 product against gray mold of strawberry, the control value of 30 g PDL-005 product against green mold of orange were 100% in 6L food storage box. The major compound of VOCs produced by PDL-005 isolate was analyzed by GC-MS. The type and content of VOCs produced by PDL-005 isloate changed with culture day and different medium or substances, and the major active compound produced by PDL-005 isolate were 2-ethyl-2-hexenal and 2,4-dimethyl-1,3-cyclopentanedione.
The PDL-005 product developed in this study showed good potential on controlling postharvest diseases. In the future, the formulation and usage of the PDL-005 product can be further optimized. Furthermore, the risk of using PDL-005 should be assessed and the control effect of PDL-005 against other pest should be further examed, or the major active compound produced by PDL-005 could be artificially generated as a biological source fumigant, instead.
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