臺灣土壤分離菌株 Bacillus spp. 對草苺萎凋病害防治效果之研究

草苺 (Fragaria x ananassa Duch.) 在臺灣屬於高經濟價值果樹之一，近年來發現草苺育苗期植株萎凋死亡之情形相當嚴重。根據近期研究，臺灣未曾記錄之草苺尖鐮孢菌 (Fusarium oxysporum f. sp. fragariae) 為造成草苺萎凋的主因之一，會造成新葉有大小葉的狀況。本研究之目的為發展草苺尖鐮孢菌的控制方法。首先對草苺尖鐮孢菌的病原接種與生長特性進行分析，再將自行篩選出具有拮抗病原菌能力、可能可促進植物生長特性且不具常用藥劑感受性之土壤分離菌株應用於草苺育苗期和本田期病害管理上，評估其維護種植株健康狀態之能力。經過病原性測試後發現，草苺尖鐮孢菌在接種濃度為 1×106 spores/mL 下，發病率及嚴重度為 20% 和 50% 左右，且會隨接種濃度提高而加重。菌絲體較適生長溫度為 28°C，而在酸鹼值為 5.0 時生長較差，與其他酸鹼值下有顯著差異。草苺的最適生長酸鹼值為 5.0 至 6.8，因此，未來或許可利用監控土壤酸鹼度的方式，來降低草苺鐮孢菌的危害。經過選擇性培養基初步篩選，從土壤分離菌株當中，挑選拮抗草苺炭疽及鐮孢菌的 595 和 376 做為主要測試菌株，此二菌株鑑定結果均屬於 Bacillus spp.，依據其拮抗能力，應可降低草苺根系遭受病原侵擾。因此，搭配具有生物防治潛力且能快速增殖之 Trichoderma spp. ML1 和 ML56 共同澆灌於植株根圈環境中來評估其對草苺病害及生長狀況之影響。綜合所有試驗結果顯示，Bacillus spp. 595 能夠有效控制病害發生率，且在短期內促進植株生長，適合於育苗期施用；然而在較為複雜之田間環境中，不論是每週或隔週的澆灌頻率，混合 Bacillus spp. 和 Trichoderma spp. 的處理會有較好的病害控制和促進植株生長效果。本研究直接於草苺產業的重要產區進行田間試驗，其試驗結果極具有產業應用價值與進一步相關研究之參考性。

關鍵字

草苺；草苺尖鐮孢菌；土壤微生物；病害抑制效果

並列摘要

Strawberry is one of the fruits with greater economic profit in Taiwan. Recently, the wilting or death ratio of seedlings and younger plants during its vegetative stage has been found severely high in Miaoli, and the newly reported Fusarium oxysporum f. sp. fragariae is one of the major causing agents of strawberry wilting in Taiwan. Plants have been diagnosed with the typical symptoms of F. oxysporum f. sp. fragariae infection, which are assymetrical plantlets, minor chlorosis and dehydration. The aim of this study is to investigate the pathogenicity and pysiological characteristics of F. oxysporum f. sp. fragariae, and the effects of soil microbes with antagonistic, plant growth-promoting and pesticide-insensitive activities on the disease incidence during vegetative and fruiting stages of strawberry growting in a nethouse or in the field. The results indicate that the incidence and severity of Fusarium wilt of strawberry inoculated with 1×106 spores/mL under greenhouse environment were around 20% and 50%, respectively, and both increased as the inoculum concentration went up. F. oxysporum f. sp. fragariae prefers 28°C and grows poorly at pH 5.0. The optimum pH for strawberry is 5.0 to 6.8, so we might be able to decrease the disease incidence of strawberry wilt by monitoring the pH value of soil or substrate. Bacillus spp. 595 and 376 were selected for evaluation and the results showed that either in a pot assay or field application, 595 is relatively suitable to be applied during the vegetative stage and combination of Bacillus spp. and Trichoderma spp. has better disease-control and plant growth-promoting effects in the field condition.