Abstract
Tomato early blight, caused by Alternaria solani, is a destructive foliar fungal disease. Herein, the potential defensive roles of benzoic acid (BA) and two of its hydroxylated derivatives, ρ-hydroxybenzoic acid (HBA), and protocatechuic acid (PCA) against A. solani were investigated. All tested compounds showed strong dose-dependent fungistatic activity against A. solani and significantly reduced the disease development. Benzoic acid, and its hydroxylated derivatives, enhanced vegetative growth and yield traits. Moreover, BA and its derivatives induce the activation of enzymatic (POX, PPO, CAT, SlAPXs, and SlSODs) and non-enzymatic (phenolics, flavonoids, and carotenoids) antioxidant defense machinery to maintain reactive oxygen species (ROS) homeostasis within infected leaves. Additionally, BA and its hydroxylated derivatives induce the accumulation of salicylic acid (SA) and its biosynthetic genes including isochorismate synthase (SlICS), aldehyde oxidases (SlAO1 and SlAO2), and phenylalanine ammonia-lyases (SlPAL1, SlPAL2, SlPAL3, SlPAL5, and SlPAL6). Higher SA levels were associated with upregulation of pathogenesis-related proteins (SlPR-1, SlPR1a2, SlPRB1-2, SlPR4, SlPR5, SlPR6), nonexpressor of pathogenesis-related protein 1 (SlNPR1), and salicylic acid-binding protein (SlSABP2). These findings outline the potential application of BA and its hydroxylated derivatives as a sustainable alternative control strategy for early blight disease and also deciphering the physiological and biochemical mechanisms behind their protective role.
Highlights
Tomato (Solanum lycopersicum L., family Solanaceae) is one of the world’s leading vegetable crops [1]
We investigated the potential of benzoic acid (BA) and two of its hydroxylated derivatives, ρ-hydroxybenzoic acid (HBA), and protocatechuic acid (PCA) as an alternative management strategy against A. solani, the causal agent of early blight on tomato
In vitro studies showed that Benzoic acid (BA) and two of its hydroxylated derivatives exhibited a strong concentrationdependent fungistatic activity against A. solani
Summary
Tomato (Solanum lycopersicum L., family Solanaceae) is one of the world’s leading vegetable crops [1]. It is grown in over 170 countries, with the total productivity of. In Egypt, the total yield of tomatoes in 2019 was 6,751,856 tonnes and the harvested area was 4.0/). Tomato’s early blight disease can destroy all aerial parts of the tomato plant including the shoot system, fruit, and at all growing stages. A. solani inhibits the photosynthesis rate in infected leaves by inhibiting photo-system II activity and decreasing the chlorophyll content [11,12]. The degradation of photosynthetic pigments caused by A. solani, causing a significant reduction in growth and a decrease in yield [12]
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