Enhancing natural disease resistance in greenhouse tomato through salicylic acid and sucrose-induced antioxidant defense against Fusarium wilt
Abstract
Fusarium wilt, caused by Fusarium oxysporum , is one of the most destructive soil-borne diseases affecting tomato ( Solanum lycopersicum L.) production worldwide, including in Algeria, where it represents a major phytosani-tary constraint. Given the limitations of conventional chemical control, this study investigated the individual and combined effects of salicylic acid (SA) and sucrose (S), applied at increasing concentrations (0.4, 0.5, and 0.6 mM), as eco-friendly elicitors of induced resistance against Fusarium oxysporum in tomato. Fifty-three fungal isolates were recovered from wilted tomato plants collected across three Algerian regions, with the most virulent isolate molecularly identified as Fusarium oxysporum with 100% ITS sequence similarity; GenBank accession PZ939396. Disease severity, photosynthetic pigments, oxidative stress markers (H₂O₂, MDA), proline content, and antioxidant enzyme activities (SOD, CAT) were evaluated under greenhouse conditions. Fusarium oxysporum inoculation caused severe disease symptoms (92% disease index), marked pigment loss, and pronounced oxidative damage. Both elicitors reduced disease severity and oxidative stress in a dose-dependent manner, with SA consistently outperforming sucrose. The combined treatment (SA+S) provided the strongest protection, achieving the lowest disease index (12%; 86.96% protection), near-complete restoration of chlorophyll content, and the highest antioxidant enzyme activities and proline accumulation among all treatments. Multivariate analyses (PCA, HCA, Pearson correlation) showed a clear discrimination between infected and elicitor-treated plants, consistent with a coordinated pattern of antioxidant and osmoprotective responses. These findings indicate that the combined treat - ment (SA+S) provides greater protection than either elicitor applied alone, an effect not previously characterized against Fusarium oxysporum . This combined benefit, evidenced through an integrated physiological and bio - chemical approach in a locally relevant Algerian pathosystem, supports the potential integration of the combined SA and sucrose treatment into sustainable Fusarium wilt management strategies.