Abstract Field surveys were conducted in 2012 and 2013 to evaluate the distribution and virulence of fungal isolates associated with tuber rot disease among yam (Dioscorea spp.) producing agroecological zones (AEZs) of Nigeria. A total of 70 and 66 farmers’ fields were surveyed in 2012 and 2013, respectively among three yam species, Dioscorea rotundata, D. alata and D. cayenensis. Fifteen rotted samples were randomly collected per each yam species in fourteen districts across the humid rainforest (HF), the derived savanna (DS) and the southern Guinea savanna (SGS) agroecologies. Twenty-one fungal species were isolated in the HF, 18 species in the DS and 16 in the SGS. The highest rot severity was in HF agroecology in the D. rotundata which varied from 27.2% to 65.7% in 2012 and from 21.1 to 57.4% in 2013, while the SGS agroecology had the least severity. Lasiodiplodia theobromae was the most virulent pathogen with lesion diameter of 26.8–42.1 mm at 14 days after inoculation. Findings provide baseline information for the formulation of management strategies for yam tuber rot disease in Nigeria.

中文翻译：

---

尼日利亚三个农业生态区从山药（薯蓣属）块茎中分离的真菌物种的分布和毒力

摘要 在 2012 年和 2013 年进行了实地调查，以评估与块茎腐烂病相关的真菌分离株在产山药（薯蓣属）的尼日利亚农业生态区 (AEZ) 中的分布和毒力。2012 年和 2013 年，分别对 70 和 66 个农田进行了调查，分别对薯蓣、D. alata 和 D. cayenensis 三种山药品种进行了调查。在潮湿雨林 (HF)、衍生稀树草原 (DS) 和几内亚南部稀树草原 (SGS) 农业生态系统的 14 个地区，每个山药物种随机收集 15 个腐烂样本。在 HF 中分离出 21 种真菌，在 DS 中分离出 18 种，在 SGS 中分离出 16 种。腐烂严重程度最高的是 D. rotundata 的 HF 农业生态学，2012 年为 27.2% 至 65.7%，2013 年为 21.1% 至 57.4%，而 SGS 农业生态学的严重程度最低。Lasiodiplodia theobromae 是毒性最强的病原体，接种后 14 天病斑直径为 26.8-42.1 mm。调查结果为尼日利亚山药块茎腐烂病管理策略的制定提供了基线信息。