發展改善芹菜連作障礙之策略

Strategies for Improvement of Succession Cropping Obstacle of Celery

劉曜德(Yao-Te Liu)

指導教授 ： 林乃君

國立臺灣大學/生物資源暨農學院/植物醫學碩士學位學程/碩士(2015年)

https://doi.org/10.6342/NTU.2015.01718

摘要

芹菜在台灣種植面積約 970 公頃，年產量約為 20,289 公噸，栽種面積多集中於雲林和彰化地區。芹菜栽培上，多年來有無法連作之問題存在，其目前解決策略主要為採用更換新地之方式來避開連作障礙問題，但此法最終將可能導致租金成本上升與無地可用之困境。過去的研究顯示，造成芹菜連作障礙的原因可能有二：一、由芹菜黃葉病菌 (Fusarium oxysporum f. sp. apii) 所導致；二、由芹菜的相剋作用所造成，此因芹菜分泌多種酚類化合物造成後作芹菜生長不良所致。因此本研究目的為釐清臺灣芹菜產區連作障礙之主因，並進一步發展利用土壤微生物改善此連作障礙之策略。結果顯示，於彰化和雲林芹菜產區採集之病株均可分離到尖鐮孢菌 (Fusarium oxysporum)，進行科霍氏法則 (Koch's postulates) 及分子與型態鑑定後，確認分離到的尖鐮孢菌為造成芹菜死亡的主要原因；經過寄主範圍測試，推測其應為芹菜黃葉病菌。本研究亦發現芹菜根部水萃液以及酚類化合物沒食子酸具有抑制芹菜種子發芽與胚根生長之現象，卻可促進F. oxysporum f. sp. apii 孢子發芽與發芽管長度，以及增加其產孢量之能力。由此結果可推斷芹菜相剋作用與 F. oxysporum f. sp. apii 有協力危害芹菜生長之可能。針對上述兩種病因，進行具防治潛力微生物之篩選，成功篩選出對芹菜黃葉病菌菌絲生長抑制率達 40% 以上之拮抗菌，AB2 與 AB78 兩菌株，於溫室進行以不同組合菌株防治芹菜黃葉病試驗，其結果顯示於不同防治時機點皆有良好防治效果。另外篩選出可於 20 小時內降解 99 % 以上沒食子酸之酚類降解細菌 PdB5-1，經由種子發芽試驗，確認 PdB5-1 可顯著改善芹菜植體水萃液抑制種子發芽之現象而提高發芽率。最後於溫室模擬田間連作障礙之環境，使用複合菌進行防治測試，結果顯示根部水萃液雖然使芹菜黃葉病之罹病度提高，但複合菌可顯著抑制土中黃葉病菌族群量，並且有效降低黃葉病之罹病度。本研究開發之複合菌證實可有效改善芹菜黃葉病發病率，可提供多年來無法解決之芹菜連作障礙問題一個新的防治策略。

關鍵字

連作障礙 ； 芹菜黃葉病 ； 尖鐮孢菌芹菜分化型 ； 相剋作用 ； 拮抗菌 ； 酚類降解菌

並列摘要

In Taiwan, the cultivation area and yield of celery are about 970 hectare and 20,289 tonne, respectively, and Changhua and Yunlin are main region for production of celery. For many years, succession cropping obstacle of celery is a serious problem in Taiwan. So far, finding the virgin lands for cultivating celery is the major improvement strategy to avoid the succession cropping obstacle problem of celery, but this improvement strategy has resulted in increased rental costs and difficulties to find suitable places for planting celery. Previous studies concluded that, succession cropping obstacle of celery could be due to (1) Fusarium oxysporum f. sp. apii (Foa) and (2) allelopathy of celery. The objectives of this study were to find out the causing agent(s) of succession cropping obstacle of celery in Taiwan, and then to develop the improvement strategies using soil beneficial microbes. The results showed that Fusarium spp. could be isolated from diseased celery plants, which were collected from the major celery production areas of Changhua and Yunlin. The pathogen was identified as Fusarium oxysporum f. sp. apii by Koch's postulates, molecular identification, morphological characteristics and a host range assay. On the other hand, aqueous extract of celery and gallic acid not only inhibited seed germination of celery, but also promoted spore germination and the germ-tube growth of Foa. These data indicated that the growth of celery may be inhibited by a synergistic effect of Foa and allelopathy in the field. We have successfully isolated the antagonistic bacteria AB2 and AB78 and the phenol-degrading bacterium PdB5-1. PdB5-1 can significantly degrade gallic acid with a degradation rate more than 99 % in less than 20 hours, and improve the growth inhibition phenomenon of seeds caused by root aqueous extract of celery. AB2 and AB78 could inhibit the growth of Foa mycelium with an inhibitory rate more than 40%, and had good control efficiency on Fusarium yellows of celery at different control timing in a greenhouse assay. In a greenhouse condition simulating the environment of succession cropping obstacle of celery in the field, mixed strains significantly reduced disease incidence and suppressed the population of Foa although the root aqueous extract of celery could increase disease incidence of Fusarium yellows. In the future, we expect to provide a new improvement strategy to reduce the loss caused by succession cropping obstacle of celery in the field using the mixed bacterial strains.

並列關鍵字

Succession cropping obstacle ； Fusarium yellows ； Fusarium oxysporum f. sp. apii ； Allelopathy ； Antagonistic bacteria ； Phenol-degrading bacterium

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