由 Fusarium proliferatum 引起之孤挺花赤斑病

Abstract

西元 2011 年 4 月與 7 月於臺中市后里地區所栽植的孤挺花花梗上，出現紅色條斑狀病徴，嚴重影響切花商品價值。田間病害調查發現，該病徵出現在花梗、葉、球莖鱗片內部與表皮及肉質根表層上，植株發病率高達 62%，傷口是主要的感染途徑。由罹病部位所分離得到之分離株在馬鈴薯瓊脂培養基 (potato dextrose agar) 上之菌落呈淡橘至粉白色，在水瓊脂培養基 (water agar) 上之小孢子呈鏈狀或假頭狀排列，分生孢子梗可為單或複瓶狀枝，但是甚少產生大孢子。依科霍氏法則 (Koch’s postulates) 完成病原性測定後，挑選供試菌株 MB-013 與 MB-020，輔以 ITS 序列比對鑑定引起孤挺花赤斑病 (red spot of amaryllis) 的病原真菌為 Fusarium proliferatum (Matsushima) Nirenberg。本病原菌菌絲最適生長溫度為 24-28°C，生長速度介於 5.2-5.9 mm/day。最適發病溫度亦為 24-28°C，低於 8°C 與高於 36°C 時則不發病。 The field survey was conducted at Houli, Taichung in April and July, 2011. The floral peduncle of amaryllis surveyed showed red spot with streak symptom appearing on cutting part one to three days after harvesting. The quality and market value of cut flower were obviously affected by disease infection significantly. Diseased symptom not only appeared on peduncle, but also on leaves, inner and surface of bulb and root surface. The disease incidence of amaryllis red spot was up to 62% in field surveys and the wound was recognized as the initial stage of disease development. The colony characteristics of isolates from diseased plants showed light orange to pink on potato dextrose agar (PDA). On water agar (WA), conidiophores of tested isolates are monophialides or polyphialides, and arrangements of micro-conidiospores are in chain or false head; however, marco-conidiospores were rare produced in WA or PDA. According to Koch’s postulates, the isolates of MB-013 and MB-020 were chosen and submitted for further molecular identification by using sequence comparison of internal transcribed spacer (ITS) of ribosomal DNA after pathogenicity test. The pathogen causing the new recorded amaryllis red spot disease was identified as Fusarium proliferatum (Matsushima) Nirenberg. Optimum temperatures for mycelial growth of pathogen were ranged from 24 to 28°C, and the growth rates were ranged from 5.2 to 5.9 mm/day. Optimum temperatures for disease development were ranged from 24 to 28°C, but nil disease symptom was observed at 8 and 36°C.