Effectiveness of certain biological agents and chemical inducers in controlling fungi responsible for root rot disease in eggplant (Solanum melongena L.)

Eggplant root rot is a serious disease affecting crop production in Babylon Province, prompting this study to investigate the incidence, causal fungi, and potential biological control methods. The results from the surveyed fields revealed that eggplant root rot was present in all regions surveyed, with infection rates ranging from 20% to 100% and infection severity ranging from 5% to 60%. Several fungi were isolated from the roots of eggplants affected by root rot. The majority of isolates belonged to Fusarium solani, which was found in 7 areas of the surveyed field with an incidence rate of 74.14%, followed by Rhizoctonia solani with an incidence rate of 36.2%. Pathogenicity tests showed that these fungal isolates infected eggplant seeds. The study also showed that Pseudomonas fluorescens inhibited the growth of both R. solani and F. solani on PDA medium, with the inhibition rate reaching 100%. Furthermore, the addition of chitosan to the culture medium at all tested concentrations also inhibited the growth of both fungi. At concentrations of 5%, 10%, and 15%, the inhibition rate was particularly high, and the inhibitory effect of chitosan increased with rising concentration. Results from the greenhouse experiment indicated that all treatments, including P. fluorescens, chitosan, and their combination, significantly reduced both the infection rate and the severity of root rot. Moreover, these treatments contributed to improved growth parameters of the eggplant plants. These findings demonstrate that P. fluorescens and chitosan, alone or combined, effectively control eggplant root rot and enhance plant growth in Babylon Province.