Copper and Manganese Increase Resistance of Clusterbean to Root Rot Caused by Rhizoctonia

Clusterbean seedlings growing in soil inoculated with Rhizoctonia were treated with either 5 or 10 ppm Cu²⁺ and Mn²⁺. Soil was inoculated by pretreatment with 250 mg (wet weight) of Rhizoctonia inoculum. A similar set of plants was maintained in uninoculated soil. Root rot incidence of plants treated with Cu²⁺ 5 ppm, Cu²⁺ 10 ppm, Mn²⁺ 5 ppm and Mn²⁺ 10 ppm was 26.6, 30.5, 11.8 and 29.2% less than the inoculated control, respectively. Inoculation with Rhizoctonia reduced chlorophyll, non‐structural carbohydrate and in vitro dry matter digestibility (IVDMD) content compared with uninoculated ones. Oxidative enzymes activities (polyphenol oxidase, peroxidase, phenylalanine ammonia lyase and tyrosine ammonia lyase), crude protein, phenolic content, structural components (acid detergent fibre, cellulose and lignin), silica, macronutrients and micronutrients increased in inoculated seedlings and this increase was further heightened by the Cu²⁺ 10 ppm treatment compared with the Cu²⁺ 5 ppm, Mn²⁺ 5 ppm and Mn²⁺ 10 ppm treatments in response to fungal invasion. It was concluded that the Cu²⁺ 10 ppm treatment may be an effective soil nutrient to provide enhanced resistance of clusterbean plants to root rot (fungal) diseases.