Diacetoxyscirpenol, a Fusarium exometabolite, prevents efficiently the incidence of the parasitic weed Striga hermonthica

Abstract

Background Certain Fusarium exometabolites have been reported to inhibit seed germination of the cereal-parasitizing witchweed, Striga hermonthica, in vitro. However, it is unknown if these exometabolites will consistently prevent S. hermonthica incidence in planta. The study screened a selection of known, highly phytotoxic Fusarium exometabolites, in identifying the most potent/efficient candidate (i.e., having the greatest effect at minimal concentration) to completely hinder S. hermonthica seed germination in vitro and incidence in planta, without affecting the host crop development and yield. Results In vitro germination assays of the tested Fusarium exometabolites (i.e., 1,4-naphthoquinone, equisetin, fusaric acid, hymeglusin, neosolaniol (Neo), T-2 toxin (T-2) and diacetoxyscirpenol (DAS)) as pre-Striga seed conditioning treatments at 1, 5, 10, 20, 50 and 100 µM, revealed that only DAS, out of all tested exometabolites, completely inhibited S. hermonthica seed germination at each concentration. It was followed by T-2 and Neo, as from 10 to 20 µM respectively. The remaining exometabolites reduced S. hermonthica seed germination as from 20 µM (P < 0. 0001). In planta assessment (in a S. hermonthica-sorghum parasitic system) of the exometabolites at 20 µM showed that, although, none of the tested exometabolites affected sorghum aboveground dry biomass (P > 0.05), only DAS completely prevented S. hermonthica incidence. Following a 14-d incubation of DAS in the planting soil substrate, bacterial 16S ribosomal RNA (rRNA) and fungal 18S rRNA gene copy numbers of the soil microbial community were enhanced; which coincided with complete degradation of DAS in the substrate. Metabolic footprinting revealed that the S. hermonthica mycoherbicidal agent, Fusarium oxysporum f. sp. strigae (isolates Foxy-2, FK3), did not produce DAS; a discovery that corresponded with underexpression of key genes (Tri5, Tri4) necessary for Fusarium trichothecene biosynthesis (P < 0.0001). Conclusions Among the tested Fusarium exometabolites, DAS exhibited the most promising herbicidal potential against S. hermonthica. Thus, it could serve as a new biocontrol agent for efficient S. hermonthica management. Further examination of DAS specific mode of action against the target weed S. hermonthica at low concentrations (≤ 20 µM), as opposed to non-target soil organisms, is required.

Modern Approaches for the Development of New Herbicides Based on Natural Compounds

“…The most active toxin, diacetoxyscirpenol ( 28 ), completely suppressed the germination of Striga hermontica (Delile) Benth. and Orobanche ramosa L. seeds at concentrations <1 µM [ 129 , 130 ]. Some natural compounds (for example, fusicoccin, strigolactones, and their derivatives), on the contrary, stimulate their seed germination in the absence of a host plant, which leads to the death of the parasites [ 131 , 132 ].…”

Modern Approaches for the Development of New Herbicides Based on Natural Compounds

“…The most active toxin, diacetoxyscirpenol (28), completely suppressed the germination of Striga hermontica (Delile) Benth. and Orobanche ramosa L. seeds in concentrations <1 µM [129,130]. Some natural compounds (for example, fusicoccin, strigolactones and their derivatives), on the contrary, stimulate their seed germination in the absence of a host plant, which leads to the death of the parasites [131,132].…”

Decoding the chemical language ofSuillusfungi: genome mining and untargeted metabolomics uncover terpene chemical diversity

“…Characterizing the identity of the metabolites involved in these interactions, and the conditions under which they are expressed, are the first steps to elucidating the diverse ecological functions of secondary compounds in environmental sensing, competition, and communication. Unlike primary metabolites, secondary metabolites are not essential to cellular functions but often play critical roles in signaling, communication, and regulating inter-and intra-species interactions between fungi and their surrounding communities [7]. To date, most studies of fungal secondary metabolic diversity have focused on pathogens, saprophytes, and endophytes, particularly those in the phylum Ascomycota [8].…”

“…Unlike primary metabolites, secondary metabolites are not essential to cellular functions but often play critical roles in signaling, communication, and regulating inter- and intra-species interactions between fungi and their surrounding communities [7]. To date, most studies of fungal secondary metabolic diversity have focused on pathogens, saprophytes, and endophytes, particularly those in the phylum Ascomycota [8].…”