Inhibitory effects of components from root exudates of Welsh onion against root knot nematodes

Abstract

Root-knot nematodes (RKNs; Meloidogyne spp.) are obligate endoparasites that infect many crops and cause severe yield losses. In this research, we studied the effect of Welsh onion, grown as a companion plant, on the resistance of cucumber plants to RKN infection and analyzed the most abundant components of Welsh onion root exudates. The results showed that, when grown with Welsh onion as a companion plant, cucumber roots had 77.0% fewer root knots and egg masses than the control cucumber roots. Welsh onion root exudates were collected and extracted with chloroform, ethyl ether, n-butanol and ethyl acetate. High concentrations of the extracts from the Welsh onion root exudates decreased the hatchability of RKN eggs. In particular, the inhibitory effect of the n-butanol extract was significant and the hatchability of RKN eggs did not exceed 10%. Gas chromatographic–mass spectrometric analysis revealed that the most abundant component in the n-butanol extract was 4-hydroxy-benzeneethanol. Treatment with 1.2 mM 4-hydroxy-benzeneethanol decreased egg hatchability to 40%, whereas treatment with 9.6 mM or a higher concentration of 4-hydroxy-benzeneethanol decreased egg hatchability to less than 10%. In addition, 1.2 mM or a higher concentration of 4-hydroxy-benzeneethanol decreased the activity of the second-stage juvenile (J2). Higher 4-hydroxy-benzeneethanol concentrations (9.8 and 19.2 mM) were lethal to RKNs to some extent, with death rates greater than 50% at 48 h of treatment. The present results suggest that cultivation with Welsh onion as a companion plant may represent an alternative to the application of synthetic nematicides, with fewer side effects. We confirmed that 4-hydroxy-benzeneethanol is a natural effective nematicide.

Effect of Intercropping Onion with Sugar Beet on Productivity of Both Crops and Root-Knot Nematodes Control under Different Onion Plant Densities and Slow-Release N Fertilizer Rates

“…The second most effective treatment in reducing root-knot nematodes, Meloidogyne spp., the number was 4rows with 80 kg nitrogen in two successive seasons. Results are in agreement with (Li et al, 2018) who showed that, when cucumber has grown with welsh onion as a companion plant, cucumber roots reduced root galls and egg-masses than the control cucumber roots. The same trend was noticed by Abdel-Baset (2007) who reported that intercropping onion with green bean reduced the root-knot nematode, M. incongita reproduction in the greenhouse.…”

“…Reducing nematode populations may due to onion root exudates consist of a variety of compounds, for example, hexahydro-3-(2methylpropyl)-pyrrolo[1,2-a]pyrazine-1,4-dione, Nformyl-tyramine, dibutyl phthalate or hexahydro-3-(phenylmethyl)-pyrrolo[1,2-a] pyrazine-1,4-dione, which involved in inhibition of root-knot nematodes activity and egg hatchability. The exudate compounds may likely have a complex interrelationship on resistance against root-knot nematodes (Li et al, 2018).…”

“…Various plants are effective in controlling nematodes on agricultural crops when grown in rotation, inter-planted with susceptible crops (Halbrendt, 1996). A variety of plant metabolites in roots and exuded from roots to the rhizosphere influence nematode behaviour, development, reproduction and even survival (Dandurand and Knudsen, 2016;Li et al, 2018). Some metabolites thus facilitate plant-parasitic nematode infection and damage, whereas others directly or indirectly reduce damage.…”

Effects of Cover Cropping on Microbial Communities Associated with Heterodera schachtii and Nematode Virulence

“…Perhaps the root exudates under field conditions stimulated the hatch of the J2, so that the bioassay also measured those nematodes present in the soil. Compounds released by plants into the soil could attract nematodes to the roots [41]. Such differences in the ratio of J2/eggs between the three types of radish bioassay were not observed at Jeinsen under the oilseed radish treatment.…”

Microplastics Reduce the Negative Effects of Litter-Derived Plant Secondary Metabolites on Nematodes in Soil

“…The nematode assay was conducted following Kim et al (2020). We focused on number of offspring as a target parameter since previous studies have pointed out that the extracts from plant litters can inhibit the hatching of embryos (Meyer et al, 2013;Li et al, 2018). Briefly, we added 0.3 g of each test soil into each well of a 24-well plate (n 6), moisturized with 82 μL of K-medium (80% of WHC).…”