Status of Phytotoxins Isolated from Necrotrophic Fungi Causing Diseases on Grain Legumes

Abstract

Fungal phytotoxins can be defined as secondary metabolites toxic to host plants and are believed to be involved in the symptoms developed of a number of plant diseases by targeting host cellular machineries or interfering with host immune responses. As any crop, legumes can be affected by a number of fungal diseases, causing severe yield losses worldwide. In this review, we report and discuss the isolation, chemical, and biological characterization of fungal phytotoxins produced by the most important necrotrophic fungi involved in legume diseases. Their possible role in plant–pathogen interaction and structure–toxicity relationship studies have also been reported and discussed. Moreover, multidisciplinary studies on other prominent biological activity conducted on reviewed phytotoxins are described. Finally, we explore the challenges in the identification of new fungal metabolites and their possible applications in future experiments.

Uncovering Phytotoxic Compounds Produced by Colletotrichum spp. Involved in Legume Diseases Using an OSMAC–Metabolomics Approach

“…However, pathogens have the ability to develop resistance to several chemical classes of compounds within a few years. This situation has decreased the efficacy of the major fungicides that are employed against crop pathogens, leading to the application of general integrated disease management strategies such as dose limitation, mixtures, and the continuous search for novel antimicrobial compounds [ 23 ]. Many plant pathogens, especially necrotrophic fungi such as Colletotrichum species, as we have seen here, are capable of producing a broad panel of natural substances representing an unexploited source of potential bio-fungicides with new molecular structures and modes of action against several crop diseases that should be tested in the near future.…”

“…The production of phytotoxic secondary metabolites is affected by environmental factors such as nutrient availability, temperature, and pH [ 23 ]. When altering these factors, it is fundamental to fully explore the structural diversity of secondary metabolites of fungal pathogens in order to induce the production of specific biomarkers that can also be useful for chemotaxonomy application [ 24 , 25 ].…”

Comparative Analysis of Secondary Metabolites Produced by Ascochyta fabae under In Vitro Conditions and Their Phytotoxicity on the Primary Host, Vicia faba, and Related Legume Crops

“…The legume-associated Ascochyta spp. produce different metabolites with pathogenesis-determining cytotoxic capacity, many of which display significant toxicity to plants [ 19 , 22 ]. To shed light on the interaction between A. fabae and its host plants and to obtain new insights into the role of secondary metabolites involved in pathogenicity, we conducted a comprehensive study to isolate and characterize the most abundant phytotoxic secondary metabolites produced by this pathogen under in vitro conditions.…”

“…Due to the difference found in the bibliography concerning the culture media described for isolation of phytotoxins produced by Ascochyta spp. [ 19 , 22 , 23 , 24 ], our study was conducted growing A. fabae on three commonly used growth media: PDB, Czapek-Dox, and rice substrate. Despite variations in culture media and substrates employed, the mycelial growth and spore production performed well.…”

“…While it has previously been isolated from A. lentis and A. lentis var. lathyri [ 22 ], this study marks its first isolation from A. fabae . Tyrosol is recognized as a phytotoxic metabolite isolated from both plants and fungi [ 38 ].…”