qRT-PCR Analysis of Silicon-induced Defense Genes in Okra Varieties under Root-knot Nematode Stress

Background: Silicon (Si) is recognized as a multifunctional element that enhances plant tolerance and improves resistance against insect pests and diseases. Okra (Abelmoschus esculentus L.), commonly known as lady’s finger or gumbo, is highly susceptible to several pests, particularly the root-knot nematode (Meloidogyne incognita), a major pathogen affecting crops of the Malvaceae family. Understanding the molecular defense mechanisms involved in silicon-mediated resistance is essential for improving crop protection strategies. Methods: Quantitative real-time PCR (qRT-PCR) was employed to analyze gene expression patterns in okra under nematode stress and silicon treatment. Reference genes were used for endogenous normalization to ensure accurate relative quantification of target genes. The expression levels of defense-related genes-PAL (Phenylalanine ammonia-lyase), CAD (Cinnamyl alcohol dehydrogenase) and CHS (Chalcone synthase)-as well as silicon transporter genes Lsi1 and Lsi2, were evaluated under disease and treatment conditions. Result: Gene expression analysis revealed significant upregulation of PAL, CAD and CHS under nematode-infected conditions, indicating activation of plant defense responses. In contrast, Lsi1 and Lsi2 showed increased expression following silicic acid treatment. The results demonstrate that silicon amendment induces a primed defense response in okra roots, enhancing resistance against root-knot nematodes. Silicon-induced resistance was strongly associated with the activation of key defense-related genes during nematode infection.