Abstract
With nematicides progressively being banned due to their environmental impact, an urgent need for novel and sustainable control strategies has arisen. Stimulation of plant immunity, a phenomenon referred to as “induced resistance” (IR), is a promising option. In this study, Cucurbitaceae COld Peeling Extracts (CCOPEs) were shown to protect rice (Oryza sativa) and tomato (Solanum lycopersicum) against the root-knot nematodes Meloidogyne graminicola and Meloidogyne incognita, respectively. Focusing on CCOPE derived from peels of melon (Cucumis melo var. cantalupensis; mCOPE), we unveiled that this extract combines an IR-triggering capacity with direct nematicidal effects. Under lab conditions, the observed resistance was comparable to the protection obtained by commercially available IR stimuli or nematicides. Via mRNA sequencing and confirmatory biochemical assays, it was proven that mCOPE-IR in rice is associated with systemic effects on ethylene accumulation, reactive oxygen species (ROS) metabolism and cell wall-related modifications. While no negative trade-offs were detected with respect to plant growth or plant susceptibility to necrotrophic pests or pathogens, additional infection experiments indicated that mCOPE may have a predominant activity toward biotrophs. In summary, the presented data illustrate a propitious potential for these extracts, which can be derived from agro-industrial waste streams.
Highlights
Causing annual crop yield losses worth an estimated 100 billion US dollar, plant-parasitic nematodes are a widespread agricultural problem (Bernard et al, 2017)
Extracts of various cucurbits were found to be potent induced resistance” (IR) stimuli, while Cucurbitaceae COld Peeling Extracts (CCOPEs) derived from melon (Cucumis melo var. cantalupensis; mCOPE) was demonstrated to be a strong nematicidal agent as well
Convening with the threshold set by De Kesel et al (2020), at least four of the six screening genes were significantly upregulated in the Rice cell suspension cultures (RCSCs) upon treatment with the evaluated CCOPEs (Figure 1)
Summary
Causing annual crop yield losses worth an estimated 100 billion US dollar, plant-parasitic nematodes are a widespread agricultural problem (Bernard et al, 2017). The group of sedentary endoparasitic nematodes is considered as most damaging for agriculture (Jones et al, 2013), with cyst nematodes and root-knot nematodes (Meloidogyne spp.) being its main representatives (Lambert and Bekal, 2002) The latter group of nematodes has a worldwide prevalence and is CCOPEs: IR Stimuli and Nematicides thought to infect most plant species. Aerobic rice production still results in lower yields, a phenomenon that has been attributed to increased prevalence and infectivity of Mg in aerobic soils (De Waele and Elsen, 2007; Kreye et al, 2009; Priyanka et al, 2012) To control nematodes such as Meloidogyne spp., the use of chemical nematicides (being pesticides that target nematodes) is possible, though unfavorable from an ecological point-of-view. Various commercial nematicides have been banned in recent years (Oka, 2020; Desaeger et al, 2021)
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