施用內生細菌增加番茄生長及抗生物性逆境之探討

番茄 (Solanum lycopersicum) 為全球溫帶地區種植面積廣大之重要經濟作物，於台灣栽培面積約 5,000 公頃，主要集中於中南部，年產量可達 12 萬公噸。番茄栽培時常遭遇許多病害的襲擊，尤以青枯病和萎凋病最為嚴重。目前有許多方式可用來進行番茄病害之管理，例如：輪作、土壤消毒、使用抗病品種或嫁接苗和施用藥劑等，但研發較安全及對生態友善的防治策略以納入番茄之綜合防治中仍有其必要性。憑藉著內生菌與植物間具緊密交互作用之利，施用具有增強植物抗性及促進植物生長能力的植物內生菌，將是促進番茄產業發展的新契機。因此，本研究藉由誘釣或直接分離法取得具潛力之番茄內生細菌，目前共分得 128 株內生細菌，接著利用培養基測試其促進植物生長相關能力，包括溶磷、螯鐵分子及生長素的合成，亦對其拮抗病原能力及是否能提高抗病能力進行測試。篩選出促進生長效果較佳之 7 株菌株 XK1-13、XP1-3、XP1-8、XP2-2、XR2-3、MK2-1 及 A7，其中以 XP1-8 及 A7 效果最為顯著，與對照組比較分別可增加番茄幼苗 30.89% 及 46.57% 之總乾重。本研究亦測試內生菌與番茄幼苗之共生位置及最佳共生條件，結果顯示內生菌共生之位置多位於植株之下胚軸，而對根長 0.2～2 公分之幼苗處理 1x108 cfu/mL 的 XP1-8 和 A7 兩菌株48 小時之共生效果最佳。此外，對峙培養試驗中，XK1-13、XP1-3 及 A7 能有效抑制番茄青枯病菌 (Ralstonia solanacearum Pss97) 之生長，於接種實驗中可見 XP1-3、XP2-2、XR2-3 及 MK2-1 具有延後番茄青枯病病程發展之效果，另外，XP2-2、MK2-1 兩菌株可降低番茄感染細菌性斑點病後之植株內菌量。最後，經由 16S rDNA 的序列分析鑑定， A7 及 XP1-8 兩菌株分別為Pseudomonas putida 及 Burkholderia tropica。

關鍵字

番茄；內生菌；促進植物生長；誘導抗病

並列摘要

Tomato (Solanum lycopersicum) is an important cash crop widely grown in temperate climates across the world. In Taiwan, approximately 5,000 ha, mainly in the middle and south parts of Taiwan, were used for tomato production, and the annual yield is about 120 thousand tons. During cultivation, tomato plants may encounter attack of different pathogens such as Ralstonia solanacearum and Fusarium oxysporum f.sp. lycopersici. Although common strategies, such as crop rotation, soil sterilization, use of resistant cultivars or grafted seedlings and application of pesticides, are available for tomato disease management, much safer and eco-friendly means are worth of development. To take advantage of the intimate interaction with plants, application of endophytes with ability to enhance tomato resistance and plant growth should shed light on improvement of tomato production. In this study, endophytic bacteria were isolated from tomato plants by luring or direct isolation, which were then used to perform assays for investigation of the plant growth-promoting activities, including phosphate solubilization, siderophore production and IAA biosynthesis. In order to understand their potentials to enhance tomato tolerance to various biotic stress, antagonistic effects against different tomato pathogens in vitro as well as pathogenicity assays was performed. One hundred and twenty-eight potential endophytic bacteria strains were isolated and tomato plants treated with 7 isolates, including XK1-13, XP1-3, XP1-8, XP2-2, XR2-3, MK2-1 and A7, showed increased biomass compared to control plants. Among these 7 isolates, the effect of XP1-8 and A7 on plant growth was more significant. They showed 30.89% and 46.57% increase in dry weight compared to control, respectively. On the other hand, the colonization sites and the colonization rates were assessed. The results showed that the endophytes mostly colonized in the hypocotyl of tomato.The highest colonization rate were detected when the tomato seedlings, whose root length is between 0.2 to 2 cm, wereco-cultured with these endophytes at the level of 1x108 CFU/mL for 48 hours. In an antagonistic activity assay, XK1-13, XP1-3 and A7 exhibited inhibitory activity on growth of Ralstonia solanacearum Pss97. In a pathogenicity assay, XP1-3, XP2-2, XR2-3 and MK2-1 caused delayed symptom development of bacterial wilt. In addition, XP2-2 and MK2-1 reduced the bacteria number of Xanthomonas perforans XTN169 in tomato leaves. At the end, A7 and XP1-8 was identified as Pseudomonas putida and Burkholderia tropica, respectively, by analysis of their 16S rDNA sequences.