| Seven endophytic bacteria isolated from papaya, snap bean and flowering dogwood were assessed for their potential as biological control agents against Phytophthora capsici Leonian and Sclerotium rolfsii Sacc, causal organisms of phytophthora blight and southern blight, respectively in several crops. All seven isolates, Serratia marcescens (B17B), Enterobacter (E), Bacillus thuringiensis (IMC8) and (Y), B. vallismortis (Ps), B. amyloliquefaciens (Psl) and B. subtilis (Prt) significantly inhibited the mycelial growth of P. capsici. However, only four isolates, E, Ps, Psl and Prt inhibited the mycelial growth of S. rolfsii. Compatibility tests between isolates showed that only B17B and Y were compatible with each other and did not interfere with each other's growth in culture and may be used together. The P. capsici isolate, Ps, Psl and Prt were tested for in vitro sensitivity to different levels of mefenoxam (Ridomil Gold SL), a chemical fungicide used to control Phytophthora diseases. The pathogen was found to be sensitive, but the bacterial isolates were tolerant to the fungicide. These results suggest that isolates Ps, Psl and Prt have potential in phytophthora blight disease management, either alone or in rotations or in combination with low levels mefenoxam to provide a more environmentally friendly and effective control of phytophthora blight disease.;In vivo greenhouse studies were conducted to evaluate the ability of Ps, Psl and Prt to reduce the severity of phytophthora blight, and promote plant growth and yield of bell pepper. All three isolates reduced the severity of phytophthora blight, and increased the shoot length, plant fresh weight, dry weight, number of fruits and fruit weight of treated plants. Although in vivo studies for southern blight have not been completed, observations from these studies indicate that endophytic bacterial isolates used in this study are promising biological control agents against phytophthora blight and southern blight. |
