Biology subjects

Rav-David, D.

Publications and source records attributed to Rav-David, D..

3 recordsLinked to original sources

bioRxiv2026

Melanoidins Suppress Cucumber and Tomato Diseases Incited by Pathogens that are Oomycetes, Bacteria and a Virus

We recently reported that solutions of the nitrogenous compounds melanoidins (M), that are formed during the final stages of the Maillard Reaction, are inducers of plant resistance (Elad et al. 2026). M promoted immunity and induced disease resistance through an effect on the transcriptome, primarily through the salicylic acid pathway. Here we tested the effect of M on plant diseases that are caused by Oomycetes, bacteria and a tobamovirus. Drench and spray of M suppressed Pythium aphanidermatum damping off in cucumber, cucumber downy mildew (Pseudoperonospera cubensis), tomato late blight (Phytophthora infestans), bacterial speck (Pseudomonas syringae pv. tomato), bacterial canker (Clavibacter michiganensis subsp. michiganensis) and the Tobamovirus Tomato brown rugose fruit virus (ToBRFV) in tomato. In various experiments control was achieved by concentrations of 0.03 and 0.1% and on older and younger leaves and even in long term experiments where the M was applied for ca 11 weeks. It can be concluded that the disease resistance inducer M can suppress soilborne and foliar diseases that are caused by Oomycetes, bacteria and a virus of the genus Tobamovirus, in addition to the fungal pathogen Botrytis cinerea reported earlier.

plant biology↗

bioRxiv2026

Phenylalanine Treatment Suppresses Necrotrophic and Biotrophic Pathogens in Mono- and Dicotyledonous Plants

L-phenylalanine (Phe) is converted via the phenylpropanoid pathway into phenolic compounds, and elevated phenolic/flavonoid levels are generally associated with enhanced plant resistance. We previously showed that exogenous Phe suppresses the necrotrophic fungus Botrytis cinerea in petunia, chrysanthemum, determinant tomato, and several postharvest diseases. Here, we expanded evaluation to a broad range of pathosystems, including an indeterminate greenhouse tomato cultivar, multiple dicot species, and the monocot wheat. Phe, applied as spray or drench across concentrations, was consistently effective at [≥]4 mM. It reduced disease severity in diverse systems: Sclerotinia sclerotiorum (tomato, sweet basil, cucumber, lettuce), Leveillula taurica and Oidium neolycopersici (tomato), Podosphaera xanthii (cucumber), wheat foliar pathogens (Blumeria graminis f. sp. tritici, Zymoseptoria tritici, Puccinia triticina, P. striiformis f. sp. tritici), the oomycetes Pseudoperonospora cubensis (cucumber leaves) and Pythium aphanidermatum (roots), bacterial pathogens (Pseudomonas syringae pv. tomato and Clavibacter michiganensis subsp. michiganensis) and Tomato brown rugose fruit (ToBRFV) that belongs to the Tobamovirus genus. Phe was effective on both young and mature leaves and often performed comparably to chemical fungicides; combinations rarely improved control, except for enhanced activity with pyrimethanil against B. cinerea in tomato. Synergistic effects were observed when Phe was combined with an adjuvant against tomato powdery mildews. A formulated product (NaturaFend 550 SP) was more effective than non-formulated Phe in B. cinerea (tomato) and P. xanthii (cucumber). Application timing also influenced efficacy, with treatment 5 days before infection providing superior control compared with 0, 3, or 7 days. Overall, Phe effectively controlled biotrophic and necrotrophic fungi, oomycetes, bacterial pathogens and a virus across diverse crops under experimental greenhouses and commercial like conditions.

plant biology↗

bioRxiv2022

Immunity priming uncouples the growth-defense tradeoff in tomato

Plants have developed an array of mechanisms to protect themselves against pathogen invasion. The deployment of defense mechanisms is imperative for plant survival, but can come at the expense of plant growth, leading to the "growth- defense trade-off" phenomenon. Following pathogen exposure, plants can develop resistance to further attack. This is known as induced resistance, or priming. Here, we investigated the growth-defense trade-off, examining how defense priming via Systemic Acquired Resistance (SAR), or Induced Systemic Resistance (ISR), affects tomato development and growth. We found that defense priming can promote, rather than inhibit, plant development, and that defense priming and growth tradeoffs can be uncoupled. Cytokinin response was activated during induced resistance, and found to be required for the observed growth and disease resistance resulting from ISR activation. ISR was found to have a stronger effect on plant development than SAR. Our results suggest that growth promotion and induced resistance can be co-dependent, and that in certain cases, defense priming can drive developmental processes and promote plant yield. Summary statementGrowth-defense tradeoffs in plants result in loss of yield. Here, we demonstrate that immunity priming in different pathways uncouples this tradeoff and allows for disease resistant plants with robust growth.

plant biology↗