接種內生菌對草莓組織培養苗生物健化之影響評估

草莓為薔薇科草本植物，為臺灣重要經濟作物，雖為宿根性植物，但在臺灣栽培時由於病蟲害嚴重且不易越夏，以至於需要年年更新母株以培育健康子苗。目前農民仍多採用自行留種的方式，自田間選取健康無病徵之植株留作下一季育苗母株使用，然而由於炭疽病菌 (Colletotrichum gloeosporioides) 潛伏感染的特性及萎凋病菌 (Fusarium oxysporum f. sp. fragariae) 會經由走莖傳播至子株等問題，如何確定母株不帶特定病原而能培育出健康種苗，成為目前在草莓育苗期亟需克服的難題。因此本研究旨在篩選草莓根部有益內生細菌，透過生物健化改善草莓組織培養苗之特性，使其能夠快速生長並具抗病性，將有助於縮短其馴化時程，並提升草莓植株對炭疽病之抗性。未來希望能將之導入草莓育苗期，協助落實以草莓種苗三級繁殖制度培育健康種苗之政策。自健康草莓根系分離出之內生細菌，首先透過培養基測試其溶磷、嵌鐵及固氮等可促進植物生長之活性，再進一步進行促進草莓營養生長試驗與提升草莓抗炭疽病能力試驗。結果顯示，生物健化 30 天後可有效提升草莓組織培養苗營養生長及抗生物性逆境能力。具促進草莓生長潛力之五株菌株中，以 Pseudomonas putida L5 效果與對照組相較下具有顯著性差異，並與前人證實可提升草莓營養生長及對生物逆境耐受性的印度梨型孢菌 (Serendipita indica) 混合施用，具有些微加乘作用，並可加速跳苗之速度，以便快速並穩定地產生大量子苗；接種後能提升草莓組織培養苗對炭疽病抗性之菌株則有四株，且本研究所篩選之內生細菌效果皆優於 S. indica，其中又以 P. fluorescens K1-3-1 效果最為顯著。此外，P. fluorescens K1-3-1 在對峙培養試驗亦可有效直接抑制炭疽病菌及萎凋病菌菌絲生長。將 P. putida L5 與 S. indica 混合施用在促進草莓營養生長能力方面極為穩定，且在提升炭疽病抗性亦有不錯的效果為本研究所得混合菌株之最佳組合。

關鍵字

草莓；內生菌；生物健化；草莓炭疽病；假單胞菌屬

並列摘要

Strawberry (Fragaria x ananassa Duchesne) is an economically important herbaceous plant belonging to family Rosaceae. Although strawberry is a perennial plant, replacement of mother plants for breeding healthy seedlings is required annually due to severe pest problems and difficulties of strawberry plants to survive over summer. Farmers are still preserving the mother plants by selecting healthy and symptomless plants from fields as the mother plants for next season. Due to latent infection of Colletotrichum gloeosporioides and infection of daughter plants by Fusarium oxysporum. f. sp. fragariae through runners, to ensure whether the mother plants are specific-pathogens-free (SPF) becomes an important issue in the strawberry nurseries. The purpose of this study was to screen beneficial endophytic bacteria from strawberry roots for biohardening of the micropropagated strawberry seedlings, making them capable of growing fast and resistant to anthracnose, and shortening acclimatization time. Hopefully, these endophytic bacteria can be introduced into the three-tier seedling production system in the near future. Endophytic bacteria isolated from the healthy strawberry roots were firstly tested for their potential in promoting plant growth activities, including phosphate solubilization, siderophore production, and nitrogen-fixation, through plate assay methods. The micropropagated strawberry seedlings after biohardening for 30 days with five endophytic bacteria, among which Pseudomonas putida L5 has the best activities, could effectively increase vegetative growth and resistance to anthracnose. Biohardening with P. putida L5 in combination with Serendipita indica, the endophytic fungus which also has the ability to enhance strawberry growth and resistance to anthracnose, could accelerate the seedling raising process, and produce abundant seedlings quickly and stably. Furthermore, four strains were selected on its ability to enhance resistance of micropropagated strawberry seedlings to anthracnose, all of which have activities superior to S. indica. Among those strains, P. fluorescens K1-3-1 has the best performance. In addition, P. fluorescens K1-3-1 could also inhibit mycelial growth of C. gloeosporioides and F. o. f. sp. fragariae in an antagonistic assay. At last, biohardening with P. putida L5 and S. indica, the best choice among all different combinations, created an excellent effect on promoting vegetative growth of micropropagated strawberry seedlings as well as increasing resistance against anthracnose at the same time.