| 摘要： 紅龍果為仙人掌科 (Cactaceae)，三角柱屬 (Hylocereus) 之多年生攀緣性多肉植物，為臺灣新興果樹之一，因大面積栽種及運輸儲存過程中病害持續發生，尤其貯藏及運輸期間管理不當，腐爛後引發的問題更是嚴重。因此本試驗調查田間紅龍果幼果上可能造成潛在果實採收後病害之真菌種類，果表總體潛在病原菌比率隨時間增加，Colletotrichum、Fusarium、Alternaria、Phomopsis 屬及 Botryosphaeriaceae 科之真菌被分離出之比率相對較高，採收後發病率以炭疽病 (Colletotrichum spp.) 及 Fusarium 果腐病 (Fusarium spp.) 最為嚴重，可高達 100%，其次為黑斑病 (Alternaria spp.) 及 Phomopsis 果腐病 (Phomopsis spp.) ，各病害之發病情形會因果園地區而不同，於田間提早套袋可降低其採收後之罹病度，但不顯著。選擇紅龍果採後發病頻率較高之倉儲病害，包含田間分離之Colletotrichum gloeosporioides TC1、Gilbertella persicaria GP1、Alternaria sp. PL3 及霧峰農業試驗所提供之果腐病 Fusarium oxysporum F213124 及 Phomopsis helianthi F213077 做為本試驗之供試菌株。使用棋盤格抑菌法 (Checkboard method) 於培養基上測試 3 種覆膜資材及 21 種植物精油之抑菌效果，覆膜資材脂肪酸鉀鹽產品 M-Pede® 及棕櫚油鉀鹽抑菌效果相當，但以幾丁聚醣做為覆膜資材最能有效抑制菌絲生長，於 10000 mg·L-1 濃度下，PL3、F213124 及 F213077 菌株抑制率達 100%；精油的部分則是肉桂葉、丁香葉及百里香精油於濃度 500 μL·L-1 對所有供試菌株之孢子發芽及菌絲生長之抑制率皆為 100%，其中丁香葉精油做為製劑開發較符合成本效益，分析丁香葉精油中之主成分為丁香酚，約佔 84.65 %，經培養基測試為主要抑菌成分。將幾丁聚醣結合丁香葉精油，於培養基上對供試菌株之菌絲抑制效果提升，幾丁聚醣與丁香葉精油結合之效果對所有供試菌株皆為加成作用。將紅龍果浸泡幾丁聚醣及丁香葉精油單獨或結合處理防治人工接種之濕腐病及炭疽病，幾丁聚醣1% (10000 mg·L-1) 結合丁香葉精油 0.05% (500 μL·L-1) 顯著降低發病率及罹病度，與殺菌劑賽普護汰寧 (護汰寧125 a.i. mg·L-1+賽普洛187.5 a.i. mg·L-1) 效果相當，但處理未接種病原菌之果實，結果較賽普護汰寧有效延遲病害發生及罹病度，且不影響紅龍果之果心硬度及可溶性固形物含量，有效維持果實品質，因此幾丁聚醣結合丁香精油具有開發為製劑之潛力，使用於防治紅龍果貯藏病害。Pitaya (Hylocereus spp.) is one of the important emerging fruit crops in Taiwan. In recent years, major post-harvest losses encountered throughout the storage time are mostly due to post-harvest diseases caused by many species of fungal pathogens. Therefore, this study investigated the potential fungal pathogen species on pitaya young fruits in the field which might cause post-harvest disease. The result showed that the number of total potential fungal pathogens isolated from fruit surface increased with time. Colletotrichum, Fusarium, Alternaria, Phomopsis and Botryosphaeriaceae were frequently observed on pitaya young fruits. For disease incidence during storage, anthranose (Colletotrichum spp.) and Fusarium fruit rot (Fusarium spp.) had the highest incidence, followed by black spot (Alternaria spp.) and Phomopsis fruit rot (Phomopsis spp.). However, disease incidences varies between different orchards. Early bagging in the field could reduce the disease severity after harvesting but the result was not significantly different. Accroding to the result, fungal pathogens, Colletotrichum gloeosporioides TC1, Gilbertella persicaria GP1, Alternaria sp. PL3, Fusarium oxysporum F213124 and Phomopsis helianthi F213077, were selected for futher testing. Antifungal effects of three coating materials and twenty one plant essential oils were tested against the five fungal pathogens by the checkboard method in vitro. M-Pede® (potassium salt of fatty acid product) and potassium salts of palm oil had the same antifungal effect, but chitosan was the most effective. At a concentration of 10000 mg·L-1, chitosan inhibitory rates of PL3, F213124 and F213077 mycelial growth were 100%. The results of essential oils antifungal activity showed that 500 μL·L-1 clove leaf oil, cinnamon leaf oil and thyme oil had 100% inhibition rate on spore germination and mycelial growth of all tested isolates. The use of clove leaf oil as a plant protection preparation is most cost-effective. The chemical composition of clove leaf oil analyzed by GC-MS and GC-FID showed that the major component was eugenol (84.65%), and inhibition experiments identified it as the main antifungal ingredient. Moreover, effect of chitosan combined with clove leaf oil on mycelial growth were also determined and their combined effects on all tested isolates were additional. The harvested pitaya fruits were soaked in chitosan or clove leaf oil alone or in combination to control artificially inoculated TC1 or GP1. 1% (10000 mg·L-1) Chitosan combined with 0.05% (500 μL·L-1) clove leaf showed markedly decreased disease incidence and severity, and were similar in effect to the fungicide cyprodinil+fludioxonil (fludioxonil 125 a.i. mg·L-1+ cyprodinil 187.5 a.i. mg·L-1). Furthermore, non-inoculated pitaya fruits soaked in 1% chitosan combined with 0.05% clove leaf were more effective in delaying the occurrence of disease compared to cyprodinil+fludioxonil, and did not affect the weight loss, firmness and total soluble solids, which effectively maintained fruit quality. These results could provide valuable information in formulating fruits protectants for post-harvest pitaya fruit in the future. |
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