Biocontrol of Rhizoctonia solani Induced Root Rot in Sugar Beet via Organic Inputs and Chaetomium globosum: Greenhouse and Field Evaluation

Rhizoctonia solani poses a significant threat to sugar beet production in Egypt, causing considerable stand losses. A study, involving 27 isolates from various governorates, revealed variable virulence, with post-emergence-damping-off ranging from 10-35%. The most aggressive isolate, RHI1, causing 35% damping-off, was selected for further evaluation. The research focused on an integrated pest management strategy combining compost with the biocontrol fungus Chaetomium globosum. Greenhouse trials demonstrated a remarkable reduction in disease incidence. Post-emergence-damping-off plummeted to 5.53% in treated plants, a significant decrease from 45.37% in untreated controls. Disease severity also fell drastically, from 65.33 to 8.37%. Results were confirmed in field trials under natural infection, where disease incidence was minimized to 10.2% in treated plots compared to 62.7% in controls. Beyond disease suppression, integrated treatment significantly enhanced vegetative growth. Treated plants in greenhouse trials exhibited superior growth parameters, including more leaves (18.67 vs. 12.33), increased height (31.83cm vs. 18.20cm), and higher fresh and dry weights. Similar improvements in yield and bulb weight were observed in field conditions. The study further elucidated the mechanisms behind these improvements. Biochemical assays revealed a strong induction of defense-related enzymes in treated plants, with elevated peroxidase and polyphenol oxidase activity. Additionally, soil microbiological analysis indicated a healthier soil ecosystem in treated plots, with increased populations of beneficial fungi, bacteria, and actinomycetes. This study supports the integration of compost and C. globosum as an effective, eco-friendly alternative to chemical fungicides for sustainable sugar beet cultivation, offering significant disease suppression (over70%), enhance plant growth, and improved soil health.