在臺灣，芹菜栽培向來存在著連作障礙的問題，過去研究顯示，導致芹菜連作障礙之原因有二：一、由 序菜黃葉病菌（Fwsan’ww f. sp.叩;7, Foa)所引起的序菜黃葉病(Fusarium yellows of celery);二、由片菜 的相剋作用（allelopathy)，即因芹菜分泌多種酚類化合物造成後作芹菜生長不良所致。本研究試圖釐清此二因 素是否會產生交互作用，而造成芹菜連作障礙加劇。結果顯示，芹菜水萃液及當中主要成分的沒食子酸，均 有抑制芹菜種子發芽與胚根生長的情形，但卻能促進芹菜黃葉病菌孢子發芽和發芽管生長，且能提高其產孢 量。另外，利用Folin-Ciocalteu法檢測芹菜根部和莖部水萃液中總酚類化合物含量變化，顯示芹菜黃葉病菌孢 子發芽與生長過程中，能降低其中的總酚類化合物含量。綜言之，種植芹菜時根系所分泌或是之後殘存於土 壤中的植物殘體滲漏出的相剋物質，除了會影響後作芹菜種子的發芽率，甚至可作為芹菜黃葉病菌孢子發芽 與生長之營養來源。由於芹菜相剋作用與芹菜黃葉病菌可能協力危害芹菜生長，未來若能找到可同時解決此 二因子的防治策略，應可有效達到減輕連作障礙所造成的損失。

In Taiwan, succession cropping obstacle has been a serious problem for celery cultivation. Previous studies concluded that succession cropping obstacle of celery could be due to (1) Fusarium yellows of celery caused by Fusarium oxysporum f. sp. apii (Foa), and (2) allelopathy of celery due to phenolic compounds produced by celery from the previous growing season. The objective of this study was to clarify whether these two factors could interact with each other to exacerbate the problem. The results showed that water extract of celery and the major phenolic compound of it, i.e., gallic acid, could inhibit germination and radicle growth of celery seed. They could also promote spore germination, germ-tube growth and sporulation of Foa. Furthermore, determination of the total phenolic content in water extract of celery using the Folin-Ciocalteu method indicated that Foa could reduce the total phenolic content during spore germination and growth. In conclusion, the allelopathic chemicals secreted from the celery roots or leaked out of the plant debris in the soil could not only affect seed germination of celery in the next growing season but also serve as nutrient for spore germination and growth of Foa. Growth of celery could be inhibited by a synergistic effect of allelopathy and Foa; therefore, in the future, if a two-pronged approach to tackle down these two factors at the same time can be developed, effective alleviation of the loss caused by succession cropping obstacle of celery in the field can be achieved.