The Antifungal Activity of Gallic Acid and Its Derivatives against Alternaria solani, the Causal Agent of Tomato Early Blight

Abstract

Tomato (Solanum lycopersicum L.) is among the most important vegetable crops worldwide. Early blight disease, caused by Alternaria solani, is a destructive foliar disease of tomato and other Solanaceae species. Herein, we investigated the in vitro antifungal properties of gallic acid and two of its derivatives (syringic and pyrogallic acids) against A. solani during 2019 and 2020 seasons. The physiological and biochemical effects of these compounds on infected tomato plants were also investigated using the whole plant bioassay. The in vitro investigation showed that all tested compounds showed fungistatic action and inhibited the mycelial radial growth of A. solani in a dose-dependent manner. In two separate pot-experiments, those compounds efficiently suppressed the development of the disease symptoms and area under disease progress curve (AUDPC), without any phytotoxic effects on the treated tomato plants. Additionally, all tested compounds positively enhanced the biochemical traits of treated plants including the chlorophyll content, the total soluble phenolics, the total soluble flavonoids, and the enzymatic activities of catalase, peroxidase, and polyphenol oxidase during 2019 and 2020 seasons. Moreover, the treatment with gallic acid and its derivatives significantly increased all yield components of A. solani-infected tomato plants such as the total number of flowers and fruits, and the fruit yield for each tomato plant in both experiments. Considering the fungitoxicity of phenolic acids against A. solani with no phytotoxicity on treated tomato plants, we believe that gallic acid and its derivatives might be a sustainable eco-friendly control strategy to reduce the usage of chemical fungicides partially or entirely against A. solani particularly, and fungal diseases in general.

Benzoic Acid and Its Hydroxylated Derivatives Suppress Early Blight of Tomato (Alternaria solani) via the Induction of Salicylic Acid Biosynthesis and Enzymatic and Nonenzymatic Antioxidant Defense Machinery

“…These findings are in agreement with our previous study where we proofed that the exogenous application of gallic acid and its derivatives efficiently suppressed the development of the disease symptoms and decreased the AUDPC on treated tomato plants [64]. Likewise, exogenous application of BA significantly reduced the disease severity and disease incidence of rice brown spot disease, caused by the ascomycetous fungus Cochliobolus miyabeanus (anamorph: Bipolaris oryzae) [65], and the cocoa vascular streak dieback, caused by basidiomycetous fungus Oncobasidium theobromae (syn.…”

“…One of the most accepted hypotheses regarding the protective role(s) of BA particularly, and phenolic compounds in general, is that role might be due to the elevated endogenous phenolics content. Herein, we showed that BA and its hydroxylated derivatives enhanced the profile of total soluble phenolics, and flavonoids in treated plants which were negatively correlated with disease progression and could directly impede the colonization of leaf tissues by A. solani , in agreement with our previous study using some other phenolic compounds [ 64 ]. Recently, it has been reported that the exogenous application of HBA significantly induced root border cells of grapevine seedlings to produce more phenolic acids [ 67 ].…”

Piriformospora indica Primes Onion Response against Stemphylium Leaf Blight Disease

“…This is exactly what may have occurred in our case, due to P. indica -derived modulation, which primed an initial boosting of CAT activity in the early stages of infection, when the level of H 2 O 2 was highest, and then resulted in increased AXP activity when H 2 O 2 became less accessible. This shift between catalytic and peroxidase activity, as the defence response induced in the plant progresses, had already been reported in tomato plants affected by early blight disease, caused by Alternaria solani [ 91 ].…”

Carbon Nanotubes Decrease the Negative Impact of Alternaria solani in Tomato Crop

“…A. solani reproduces asexually by multicellular conidia that can form necrotic lesions 2–3 days after infection and reproduce new conidia 3–5 days later, this disease cycle allows a polycyclic infection, and can infect all aerial parts of the plant, including leaves, stem, and fruits. Furthermore, being a necrotrophic fungus, it kills host tissues using the enzymes cellulase and pectin methyl galacturonase and producing numerous toxins [ 3 , 4 ]. The first foliar symptoms in the tomato plant become visible on the lower and older leaves after the emergence of the fungus in the form of dark-colored lesions recognized by their distinctive concentric rings, in addition to necrotic lesions on the stem [ 5 ].…”

“…Under favorable conditions, mature lesions are usually covered by a black mass of mycelia and fungal spores. Additionally, A. solani can cause complete defoliation, substantial yield losses, and plant death if not managed properly [ 3 ]. The loss of productivity due to infection by A. solani in tomato can be up to 80% [ 1 ].…”