Metarhizium spp.
are widely used as
biocontrol
agents against insect pests, but the chemical basis underlying their
nematicidal activity remains largely unknown. Here, bioassay-guided
fractionation and GC–MS identified dimethyl disulfide (DMDS)
and dimethyl trisulfide (DMTS) as the major volatile nematicidal compounds
produced by Metarhizium anisopliae .
Both compounds exhibited concentration-dependent activity against
three plant-parasitic nematodes (PPNs), with 24 h LC 50 values
of 0.19–1.38 μg/mL for DMDS and 0.04–0.07 μg/mL
for DMTS. In tomato pot trials, the fermentation broth achieved 79.49%
control efficacy against Meloidogyne incognita , significantly higher than abamectin (68.24%). The GFP-labeled fungus
colonized tomato roots and persisted in the rhizosphere for 60 days.
Molecular docking and physiological assays suggested that DMDS and
DMTS disrupt calcium homeostasis, impair mitochondrial function, and
induce ROS accumulation. These findings provide new insight into the
volatile-mediated nematicidal activity of M. anisopliae and support its development as an environmentally friendly bionematicide.
Jing Wang,Tong Zheng,Chen Cai,Yanxiang Zhang,Huiling Liu
The oxidation of ethanethiol (C 2 H 5 SH), as a representative odorous pollutant, by ferrate (Fe(VI)) in aqueous alkaline solution was investigated to understand its kinetics, stoichiometry, and reaction pathways. The reaction kinetics and fraction of different intermediates were found highly dependent on pH. The reaction behaved as a 5/2-order reaction in a pH range of 8.0–10.0, and a second-order reaction in a pH range of 10.5–12.0. The rate constants decreased with increased pH, and the speciation of Fe(VI) and C 2 H 5 SH during the reaction were further discussed. C 2 H 5 SH was finally oxidized to nonvolatile and odorless sulfonic acid (C 2 H 5 SO 3 H) with the intermediates of sulfinic acid (C 2 H 5 SO 2 H) and disulphide (C 2 H 5 SSC 2 H 5 ). A plausible mechanism involving two competing reactions for C 2 H 5 S radicals was proposed to explain the pH-dependent reaction order. In addition, kinetics and products of C 2 H 5 SH degradation by Fe(VI) were compared with other oxidants (O 3 , chlorine, ClO 2 , KMnO 4 , H 2 O 2 , and OH). Our results provided a deep understanding of C 2 H 5 SH degradation by Fe(VI) in aqueous alkaline solution.
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