河北省甘薯镰孢菌腐烂与溃疡病的病原鉴定
Identification of the pathogens causing Fusarium root rot and stem canker on sweet potato in Hebei Province

为明确河北省甘薯镰孢菌腐烂与溃疡病的症状特点和病原种类,在不同种植区采集储藏期和育秧期病样,描述其症状特征;对病原菌进行分离纯化,采用柯赫氏法则回接验证,依据病原菌的形态特征和基因序列确定病原菌种类。结果表明,在储藏期甘薯发病可导致薯块表面腐烂的占总病薯的59.09%,端部腐烂的占40.91%;薯块带有褐色轮纹病斑的占61.36%,病斑没有轮纹或者轮纹不明显的占38.64%;发病初期薯块内部病斑浅、黑褐色的占27.27%,发病后期薯块内部形成空腔、布满白色菌丝的占72.73%;病斑带有苦味的占59.09%,病斑没有苦味或苦味不明显的占40.91%;在育秧田发病导致薯秧溃疡,表现为主茎基部呈点片发生黑色或者褐色病斑,部分有开裂。分离的病原菌能够同时侵染薯块和薯秧;病原菌单瓶梗产孢,大型分生孢子稍弯,两端钝圆,多数3~7个分隔,顶细胞钝圆,基细胞足跟较明显。其rDNA-ITS、EF-1α、β-tubulin基因序列与茄镰孢菌Fusarium solani的同源性分别为97%、99%和98%。初步确定甘薯镰孢菌腐烂与溃疡病的病原菌为茄镰孢菌F. solani。
In order to confirm the symptoms and the pathogen of sweet potato Fusarium root rot and stem canker, the symptoms were described based on the diseased sweet potato storage roots and stems collected from different areas in Hebei Province. The pathogen was isolated from diseased samples and confirmed according to Koch's law, which was identified based on morphological and molecular characteristics. The results showed that the pathogen caused surface rot (59.09 percent of the total diseased samples) or end rot (40.91%) on the storage roots of sweet potatoes. The lesion surface consisted of alternating light and dark brown concentric rings (61.36%) that were darker than the roots surface, but the concentric ring was sometimes unconspicuous (38.64%). Cutting the diseased roots revealed that the lesions developed shallow with dark brown in early stage (27.27%), but it could extend into the center of the roots often with cavities within the lesion that were lined with white mycelia of the fungus in later stage (72.73%). The necrotic tissues smelled bitter (59.09%) or the bitter smell was not conspicuous (40.91%). On the nursery, it caused cankers with dark brown to black lesions on the lower portions of underground stems, occasionally ruptured. All pathogens isolated could infect both root and stem. Conidiogenous cells were produced on monophialides. Macroconidia curved slightly, three to seven septate with rounded ends. Apical cells were blunt and rounded. Basal cells had a distinct foot shape. The rDNA-ITS, EF-1αandβ-tubulin sequences of the pathogen shared 97%, 99% and 98% homology with those of Fusarium solani, respectively. The pathogen causing Fusarium root rot and stem canker was confirmed to be F. solanibased on its morphological and molecular characteristics.