台灣北部甘藷基腐病及乾腐病之研究

Abstract

甘藷基腐病(Phomopsis destruens)為國內近年來發生之新病害，造成甘藷莖腐、萎凋及塊根腐爛等病徵，損失可達五至六成。甘藷乾腐病(Diaporthe batatatis)亦為國內晚近被紀錄之病害，病徵及發病生態皆與基腐病具高度相似性。以往此兩種病害之報導多集中於中南部，而臺灣北部之新北市金山區及萬里區之甘藷田亦於2012年開始出現類似病徵，故本研究自2012年10月起至新北市金山區、萬里區、台北市文山區、大安區、新竹縣竹北市等地之甘藷田進行病害調查、採樣及病原分離鑑定等工作。本研究總共自發病甘藷植株分離到655基腐型菌株及64乾腐型菌株。基腐病菌之菌落於potato dextrose agar上之形態為菌絲灰白色至淺褐色平鋪狀，不規則形並具有波浪狀邊緣，培養後期表面產生黑色柄子器，甲型分生孢子單孢無色，長圓形，長寬為6-9 × 3-4 μm；乾腐病菌於PDA上之形態為菌絲白色平鋪狀，不規則形，邊緣葉狀，後期長出黑色柄子器，柄子器多具長喙，甲型分生孢子單孢無色，擬紡錘形，長寬為7-9 × 2-2.5 μm。經接種試驗，確認基腐病及乾腐病菌皆可藉傷口感染塊根，而基腐病菌可藉傷口及葉痕感染莖部。上述甘藷基腐病及乾腐病代表性菌株經DNA片段之PCR增幅及ITS序列分析比對，已確認分別與Phomopsis destruens及Diaporthe batatatis)有最高的相似度而完成菌種之鑑定。，甘藷基腐病菌在30℃下有最高之生長速率，甘藷乾腐病菌則在25℃下有最高之生長速率，兩種病原菌皆在35℃下生長緩慢，15℃下仍可生長。基腐病菌之孢子在黏質土壤中可殘存一週，菌絲在組織塊中埋於黏質土壤則可殘存一個月。藥劑測試方面，共有7種對子囊菌有效之殺菌劑被選列進行測試，結果發現腐絕快得寧、免賴得及甲基多保淨對此二病原之菌絲生長有最佳之抑制效果；在3種非農藥資材中則以4-4式波爾多液對菌絲生長之抑制效果亦佳。盆苗之病害防治試驗則發現以腐絕對基腐病及乾腐病具最高之防治潛力。

Foot rot of sweet potato, caused by Phomopsis destruens, is a new disease that occurred in recent years in Taiwan. This disease caused stem rot, wilt and root rot symptoms on sweet potato and reduce the yield up to 50-60%. Dry rot of sweet potato, caused by Diaporthe batatatis, is also a newly found disease in Taiwan, with quite similar symptoms and epidemic pattern to those of foot rot disease. In the past, both diseases were reported mostly in southern and central Taiwan, but since 2012 similar symptoms had been found in northern Taiwan, including Jinshan district and Wanli district, New Taipei City, causing great damage to the industry. Therefore we started to investigate the occurrence of these diseases since October, 2012. The diseased samples were diagnosed and collected from plantations located at Jinshan and Wanli district, New Taipei City, Daan and Wenshan district, Taipei City, as well as Zhubei, Hsinchu City. A total of 655 and 64 fungal isolates were obtained from diseased samples and preliminarily identified as Phomopsis destruens and Diaporthe batatatis, respectively. The colony of P. destruens isolates on PDA were grey to light brown, flat , irregular shape with undulate margin, producing black pycnidia on the surface in late stage. α-conidia one-celled, hyaline, oblong, 6-9 × 3-4 μm. The colony of D. batatatis isolates on PDA were white, flat, irregular shape with lobate margin in early stage, then producing black pycnidia with long beak in late stage. α-conidia one-celled, hyaline, fusoid, 7-9 × 2-2.5 μm. After inoculation of both typical isolates on healthy roots through wound, the roots developed identical foot rot or dry rot diseases as those found in the field, fulfilled the Koch’s Postulates for both diseases. The foot rot pathogen was also proven to be able to inoculate through stem wound and leaf scar. The optimal growth temperature for foot rot pathogen was 30℃, but for dry rot pathogen it was 25℃. They both can not grow well at 35℃, but can still grow at 15℃. The survival of condinia of foot rot pathogen in field soil was limited to within one week, although the pathogen in diseased tissue can survive for longer than one month. We have test 7 anti-ascomycetes fungicides for controlling both diseases. Results showed that thiabendazole+ oxine-copper, benomyl, and thiophanate-methyl were able to inhibit the mycelial growth of both pathogens. Among 3 non-pesticides, only the bordeaux mixture (4-4 type) showed some growth inhibition effects on the pathogens. However, in pot plant tests, only thiabendazole showed good controlling results to both pathogens.