Abstract
We reported formerly that cyclamen plant grown under excess nitrogen tends to induce Fusarium wilt disease. The present investigation was undertaken to examine the nitrogen compounds, which promote the growth of infected Fusarium and accelerate wilt symptom of cyclamen shoot. High levels of asparagine, glutamine and arginine were detected in cyclamen tubers, which were stained with Fusarium. All of these amino acids showed in vitro stimulation of Fusarium growth. Treatment with high ammonium sulfate resulted in the accumulation of glutamine in underground part of cyclamen plant. Furthermore, 15N-labelled glutamic acid, when absorbed from cyclamen root, was immediately transformed to glutamine in the root and transported to the tuber possibly through xylem vessel. These results strongly suggest that glutamine, asparagine and arginine, which are synthesized with the assimilation process of excess nitrogen, promote the growth of Fusarium infected within xylem tissue and finally induce wilt symptom of cyclamen shoot.
