Plant RNA interference from antiviral silencing to multiplex trait engineering for climate-resilient crops.

RNA interference (RNAi) in plants has evolved from an unexplained antiviral and transgene interference phenomenon into a general regulatory platform for sequence-guided gene suppression, chromatin control, systemic signaling, and phenotypic plasticity. This Review synthesizes six decades of plant RNAi, tracing its progression through conceptual bottlenecks and technological solutions. Early work established that RNA-derived homology could suppress viral infection and transgene expression. Mechanistic studies then revealed a diversified plant silencing system involving Dicer-like proteins, Argonautes, RNA-dependent RNA polymerases, systemic movement, and RNA-directed DNA methylation. In parallel, RNAi moved into crop design, enabling targeted modification of yield, fiber quality, flowering, disease resistance, allergenicity, fertility, plant architecture, lignin content, nutrient composition, and pest resistance across diverse species. Importantly, RNAi is not merely a historical precursor to genome editing. It retains distinct value because it can tune gene dosage, silence multigene families, uncover compensatory network responses, and perturb upstream regulatory nodes, such as phytochrome RNAi in cotton, where partial suppression simultaneously improves several negatively correlated traits. Most recently, host-induced silencing, spray-induced dsRNA, nanocarrier delivery, and CRISPR-associated RNA tools have repositioned RNAi as a versatile breeding platform. The future lies in convergence with genome editing, using pangenome-informed, allele-aware target design and combined RNAi-editing pipelines. The lesson learned is that useful crop engineering often requires rebalancing endogenous networks rather than permanent gene knockout. In this review, the historical developmental phases are used carefully: the formal molecular term RNA interference emerged in the late 1990s, while earlier plant work on antiviral resistance, co-suppression and post-transcriptional gene silencing anticipated the same sequence-guided logic. At the same time, practical deployment remains constrained by variable knockdown, off-target risk, construct instability, environmental degradation of sprayed RNA, delivery cost, resistance evolution in target pests or pathogens, regulatory classification, and public acceptance; these constraints are discussed as platform-specific design and risk-assessment issues rather than as generic barriers.