Priming effect of root-applied silicon on the enhancement of induced resistance to the root-knot nematode Meloidogyne graminicola in rice

Abstract

BackgroundSilicon (Si) can confer plant resistance to both abiotic and biotic stress. In the present study, the priming effect of Si on rice (Oryza sativa cv Nipponbare) against the root-knot nematode Meloidogyne graminicola and its histochemical and molecular impact on plant defense mechanisms were evaluated.ResultsSi amendment significantly reduced nematodes in rice roots and delayed their development, while no obvious negative effect on giant cells was observed. Increased resistance in rice was correlated with higher transcript levels of defense-related genes (OsERF1, OsEIN2 and OsACS1) in the ethylene (ET) pathway. Si amendment significantly reduced nematode numbers in rice plants with enhanced ET signaling but had no effect in plants deficient in ET signaling, indicating that the priming effects of Si were dependent on the ET pathway. A higher deposition of callose and accumulation of phenolic compounds were observed in rice roots after nematode attack in Si-amended plants than in the controls.ConclusionThese findings indicate that the priming effect may partially depend on the production of phenolic compounds and hydrogen peroxide. Further research is required to model the ethylene signal transduction pathway that occurs in the Si-plant-nematode interaction system and gain a better understanding of Si-induced defense in rice.

Silicification of Root Tissues

“…On the other hand, significant positive effects of Si were observed in soybean, common bean, and rice [161]. After Si-treatment, the genes were overexpressed in more resistant cultivars of rice, playing a role in defense via the ethylene signaling pathway, and roots deposited more callose and phenolic compounds compared to Si-non-treated plants [149].…”

“…These biotic stressors cause retardation of growth, yield production, and shortening of lifespan in hosts. According to the experimental studies, Si in plant roots can alleviate the stress after bacterial [140][141][142], fungal [143][144][145], insect [146,147], nematode [148,149], and plant [150,151] attack, but also stress from auto-toxicity of the same plant [152]. The level of its beneficial effect is Si concentration dependent.…”

Silicon modulates multi-layered defense against powdery mildew in Arabidopsis

“…3) or overexpression of PMR4/GSL5 (Ellinger et al 2013) confers resistance to powdery mildew. Lastly, PAD4-dependent resistance to aphids is also associated with increased callose deposition (Rashid et al 2017), similar to Simediated resistance to insects (Yang et al 2018) or even nematodes (Zhan et al 2018), despite that in the latter cases whether resistance is PAD4-dependent remains to be tested. Therefore, it is possible that PAD4 (but not EDS1) may play a critical role in the deposition of a basal level of PMR4-dependent callose to papillae, thus explaining the PAD4-dependence of high Si-mediated resistance against powdery mildew pathogens.…”

αβ-Dehydrocurvularin isolated from the fungus Aspergillus welwitschiae effectively inhibited the behaviour and development of the root-knot nematode Meloidogyne graminicola in rice roots

“…Nipponbare) were originally obtained from the US Department of Agriculture (GSOR-100) and multiplied in Hunan Province, China. Seeds were soaked in 5.25% sodium hypochlorite for 5 min and germinated at room temperature (25 ± 4°C) for 4 d. One geminated seed was sown in a polyvinylchloride (PVC) tube containing synthetic absorbent polymer (SAP) [43]. Rice seedlings grew in a greenhouse and were irrigated with 20 ml of Hoagland's solution twice per week at 28 ± 2°C with 70-75% relative humidity.…”

“…The M. graminicola population was propagated on the susceptible rice variety Nipponbare at 28 ± 2°C. Nematode eggs were separated from the root galls and hatched in a 75-μm sieve at room temperature for 3-5 d. Hatched second-stage juvenile (J2) suspensions were filtered through a 25-μm sieve and resuspended in distilled water at approximately 200 nematodes mL − 1 for the subsequent experiments [27,43].…”