Induction of Systemic Resistance in Cluster Bean Against Damping-off and Root Rot Diseases

Abstract

Efficacies of three abiotic inducers (systemic resistance agents) i.e., bion, humic acid (HA), salicylic acid (SA), compared to Rizolex-T50 as seed treatments were tested against damping-off and root rot diseases of cluster bean (Cyamopsis tetragonoloba L.) in pot and field experiments. In green house, pathogenicity test indicated that the three tested fungi were pathogenic and caused emergence damping-off. R. solani caused the highest percentage of pre-emergence damping-off. Moreover, the lowest percentage of survived plants was occurred under F. oxysporum and R. solani (26.7% for each). Rizolex-T50 presented the highest reduction in disease parameters in infested soil with the three fungi, Bion came next to the fungicide followed by humic acid then salicylic acid. All the investigated treatments significantly increased the activity of chitinase, β-1, 3-gluctronase, peroxidase (PO), polyphenol oxidase (PPO), phenylalanine ammonia-lyase (PAL) enzymes. As well as total content of phenolic compounds and total content of lignin were increased in cluster bean plants grown in artificially infested soil with the three tested fungi (Fusarium oxysporum, Rhizoctonia solani, and Macrophomina phaseolina) each alone compared with untreated control. In field, pre sowing seed treatments with the desired inducer of resistance inducer caused considerable increase in the photosynthesis pigments (chlorophyll-a, chlorophyll-b and total chlorophyll) and seed quality (total nitrogen and total protein). In general, the highest figured data of the increase in the cluster bean tissue were associated with the inducer resistance agents i.e., Bion, salicylic acid and humic acid, respectively, followed by seed treatment with the fungicide Rizolex-T50. Whereas the lowest increase was shown in control treatment. It could be concluded that any of bion, HA or SA can act as inducer of systemic resistance in cluster bean plant against infection by each of Fusarium oxysporum, Rhizoctonia solani, and Macrophomina phaseolina infections. Consequently, these agents could be recommended for management damping-off and root rot diseases in cluster bean plants and improving photosynthetic pigments and seed quality.