Valutazione di batteri endofiti come antagonisti efficaci nel contenimento della tracheofusariosi della lattuga

The plant microbiota, in addition to being a promoter of the land plants evolution 700 million years ago, is a constitutive element that determines the health and productivity of the host plant. All plant tissues host endophytic microbial communities that establish interactions with the host plant and other microorganisms, conferring advantages such as protection from phytopathogens and growth promotion. These characteristics make endophytic microorganisms excellent candidates as biological control agents. Lettuce is one of the most important crops for quantity of production among leafy vegetables. However, each year there are large crop losses due to several phytopathogens, among which Fusarium oxysporum f.sp. lactucae (FOL), agent of lettuce Fusarium wilt disease, is one of the most dangerous. In this study, the biocontrol efficacy of 6 endophytic bacteria (Bacillus subtilis LL03, B. subtilis LR01, Kosakonia cowanii LL01, Escherichia hermannii LL07, Enterobacter cloacae LL04VRBA, Pseudomonas horyzihabitans LL18), isolated from root and leaf endosphere of lettuce (Lactuca sativa L.) plants, was assayed against F. oxysporum f.sp. lactucae race 1 and race 4, both in vitro and in vivo. The in vitro biological control test was carried out by co-culturing F. oxysporum f.sp. lactucae with endophytic bacteria on PDA medium, incubated at 25°C for 1 week. B. subtilis LR01 and LL03 inhibited mycelium growth by 37.21% and 37.50% against FOL race 1 and by 40.68% and 24.96% against FOL race 4. The in vivo test was performed in greenhouse at 24°C by monitoring symptoms at 14, 21, and 28 days after inoculation. The trial performed against FOL race 1 showed that treatments performed with B. subtilis LR01 and LL03 significantly reduced the average disease index, followed by K. cowanii LL01 and E. hermanii LL07, compared to the inoculated and untreated control. Additionally, the treatment performed with E. hermannii LL07 showed the significantly highest average lettuce biomass commercial weight (147.30 g), followed by B. subtilis LR01 (132.70 g) and K. cowanii LL01 (123.38 g), compared to the inoculated and untreated control (52, 94 g). The trial performed against FOL race 4 showed that all treatments significantly reduced the average disease index 21 days after inoculation, whereas no significant differences were found in comparison with inoculated and untreated control after 28 days. Among the disease management measures currently adopted to control lettuce Fusarium wilt, the most effective is the use of resistant cultivars. Using biocontrol agents, such as endophytic bacteria that can be easily combined with the use of resistance cultivars, could be an ideal option to reduce crop losses and improve plants growth.