Groundnut root rot is a complex disease affecting the crop production worldwide. The objectives of this study were to: (1) assess the occurrence and distribution of groundnut root rot complex in four main groundnut-growing areas of eastern Ethiopia; (2) identify the major pathogens associated with groundnut root rot complex; and (3) determine the role of pathogens singly and in combination on root rot severity of groundnut under greenhouse conditions. A total of 240 groundnut fields were surveyed over two seasons, and 75% of the fields were infected with root rot complex. Mean percent disease prevalence and incidence were highest in Babile, followed by Gursum, while Darolebu had the lowest. Fusarium oxysporum (Fo) was the most common fungus isolated from infected groundnut roots, followed by F. solani (Fs) and Rhizoctonia bataticola (Rb). Other fungi less frequently isolated included Sclerotium rolfsii (Sr) and R. solani (Rs). The pathogenicity test showed that all isolated fungi were pathogenic to groundnut, with Fs being the most virulent in causing root rot, followed by Rb and Fo, while Sr and Rs were less pathogenic. Disease severity was higher on plants co-inoculated with Fo, Fs and Rb than with either alone. The Fs, Fo and Rb were found to be the major causal fungi associated with groundnut root rot complex in eastern Ethiopia, with Fs being the most important and destructive pathogen in the complex and acted as synergistic pathogen with Fo and Rb; thus, breeding for resistance and management strategies should focus on these pathogens.
Keywords: Fusarium oxysporum, Fusarium solani, Incidence, Pathogenicity, Pathogen interaction, Prevalence, Rhizoctonia bataticola, Severity