Effect of cover crops on the suppressiveness of root rot and on the agronomic performance of cassava

Cassava (Manihot esculenta Crantz) is a major staple food in many developing countries, including Brazil. However, it faces significant challenges due to diseases such as dry root rot (DRR) and black root rot (BRR) caused by soil-borne plant pathogenic fungi. This study explored the use of cover crops to suppress these diseases and to improve the agronomic traits of cassava. Over four cultivation cycles, various cover crops (sunn hemp, black oat, jack bean, maize, peanut and cowpea) were alternated with cassava varieties 'BRS Kiriris' (resistant) and 'BRS Formosa' (susceptible) in soil infested with DRR (Fusarium oxysporum, F. equiseti, F. verticillioides, F. solani, F. lateritium, F. chlamydosporum) and BRR (Lasiodiplodia theobramae, Neoscytalidium dimidiatum) pathogens. In the 2nd cycle, only germination showed significant differences, but by the 4th cycle, various agronomic parameters, including fresh weight (FW.AP), dry weight (DW.AP) of the aerial part, fresh weight (FW.Root), dry weight (DW.Root) of the roots, and plant vigor. Cowpea was identified as the most effective cover crop for reducing the disease index (DI %) by promoting healthier and taller cassava plants. Jack beans and peanuts also had positive effects on vigor, FW.AP, DW.AP, FW.root, and DW.root. In contrast, maize, black oats, Crotalaria ochroleuca, cassava, and fallow soils had minimal impacts. Throughout these cycles, the selected cover crops consistently contributed to disease reduction and improved the agronomic performance of the cassava. This study highlights the potential of holistic disease management strategies.