Evaluation of the Biological Control Agent’s Efficiency Against the Causal Agent of Early Blight of Solanum melongena

Eggplant, an important vegetable crop in Iraq, faces yield losses due to early blight disease caused by Alternaria solani. Two antagonistic fungi (Aspergillus niger and Purpureocillium lilacinum) isolated from eggplant rhizosphere were tested in vitro (dual confrontation technique) and in vivo (preventive treatments) as potential bioagents against the most virulent A. solani isolates. A. niger and P. lilacinum at 30% conidia/ml exhibited high inhibitory rate (55.11%) against A. solani mycelial growth. Furthermore, these two antagonistic species when applied preventively at 30% of the stock conidial suspension in vivo, reduced significantly disease severity index (<28.41%). Moreover, A. niger (11.98 units/g of soluble protein) and P. lilacinum (8.11 units/g of soluble protein) enhanced the polyphenol oxidase activity. Based on the results obtained by this study, it appears that A. niger and P. lilacinum could be employed as foliar treatments against A. solani to promote eggplant growth and development and induce plant systemic resistance. To control A. solani, it is encouraged to use natural enemies as components in integrated disease management. Keywords: Alternaria solani, biological control, polyphenol oxidase, Solanum melongena, antagonistic fungi