In vitro screening of antimicrobial potential of Myrtus communis extract against Xylella fastidiosa subsp. pauca, multiplex and fastidiosa

Xylella fastidiosa is a Gram-negative bacterium respon-sible for severe damage to several economically impor-tant crops worldwide. The absence of effective and sus-tainable management strategies highlights the urgent need for innovative antibacterial solutions. Screening plant-derived extracts for antimicrobial activity may offer promising alternatives for the control of xylem-colonizing pathogens, including X. fastidiosa. In this study, in vitro well diffusion and broth dilution assays were performed to evaluate the antimicrobial activity of Myrtus communis extract against X. fastidiosa subspecies pauca, multiplex, and fastidiosa, all reported in Apulia. Clear inhibition zones (ranging from 4 to 20 mm) were observed for all tested subspecies compared to the con-trol. Moreover, Myrtus extract significantly reduced the growth of X. fastidiosa subsp. pauca by 45% after 336 hours in liquid cultures. Similar inhibitory effects were recorded for the other subspecies: a remarkable 75% growth reduction for subsp. multiplex and a 40% reduc-tion for subsp. fastidiosa, relative to their respective controls. These findings suggest that Myrtus communis extract exhibits notable antimicrobial potential against different X. fastidiosa subspecies. However, further inves-tigations under in vivo conditions are necessary to vali-date its efficacy and assess the feasibility of incorporat-ing such natural products into integrated management strategies for Xylella-associated diseases.