番茄萎凋病菌厚膜孢子之逆境抗性分析

Analysis of stress resistances of chlamydospores of Fusarium oxysporum f. sp. lycopersici

番茄萎凋病菌（Fusarium oxysporum f. sp. lycopersici）是番茄的重要真菌性病原菌，可長期存活於土壤中，也是造成連作障礙的重要因子之一，其厚膜孢子是存活於土壤中的重要構造，較分生孢子具有更強的耐受逆境能力，惟番茄萎凋病菌的厚膜孢子對逆境的耐受特性卻鮮有研究報導。本研究利用栽培介質萃取液誘導番茄萎凋病菌產生厚膜孢子後，在不同的環境因子下比較厚膜孢子與小分生孢子間的發芽能力和構造差異。研究結果顯示，厚膜孢子較小分生孢子對於危害番茄幼苗具有較高的接種潛勢。此外，在高溫、高pH值、高滲透壓、高含量過氧化物及高濃度剛果紅等逆境下，厚膜孢子的發芽率皆優於小分生孢子。60℃以上的熱處理及超過50 ppm的鋅錳乃浦處理均可有效抑制厚膜孢子的發芽能力。進一步，以螢光染色觀察發現厚膜孢子比小分生孢子具有較厚的幾丁質細胞壁，且含較多的肝醣及脂質。本研究證實番茄萎凋病菌之厚膜孢子均比小分生孢子更具耐受多種逆境之特性。

"Fusarium oxysporum f. sp. lycopersici is an important fungal pathogen of tomato. It is able to survive in soil for several years, and is one of the important factors resulting in continuous cropping obstacle of tomato. It is considered that chlamydospores are the important survival structure of the pathogen and are more tolerant to environmental stresses than conidia. However, the scientific reports of chlamydospore resistant abilities to environmental stresses are still lacking in studies of F. oxysporum f. sp. lycopersici. Here, chlamydospores of F. oxysporum f. sp. lycopersici race 2 isolate CT-Fo-5 induced from sterilized potting soil broth were used to compare with microconidia on germination under stress conditions and on biological structures. Results indicated that chlamydospores displayed higher inoculum potential of causing tomato seedling wilt than microconidia. Chlamydospores showed higher germination than microconidia under high temperatures, high pH values, high osmotic pressures, high oxidative stresses and high concentrations of Congo red. Germination of chlamydospores was effectively inhibited by high temperature (>60℃) and mancozeb (>50 ppm). In addition, it was observed under fluorescent staining that chlamydospores contain thicker chitin cell wall and more abundant glycogen and lipid than microconidia. The study provides evidences that chlamydospores of F. oxysporum f. sp. lycopersici are more resistant to environmental stresses than microconidia."