Osmoprotectant-mediated stress mitigation in rainfed field crops: Biosynthetic cascades, physiological mechanisms, and agronomic intervention frameworks for drought-resilient production systems

India’s rainfed agricultural matrix, encompassing 51.12% of the net sown area and sustaining livelihoods of approximately 80% of small and marginal farmers, confronts escalating abiotic stress pressures chiefly drought, heat, and secondary osmotic derangements that compromise physiological homeostasis and depress field-crop productivity. The accelerating frequency of terminal heat events and erratic monsoon distribution necessitates bio-molecular interventions that extend beyond conventional agronomic management. Rainfed farming is mainly affected by irregular rainfall, dry spells, drought and high temperature, which often lead to inadequate soil moisture and unstable crop yields. Moisture stress during critical growth stages can reduce photosynthesis, nutrient uptake and reproductive growth. Hence, there is a need for simple, climate-resilient management practices that help crops withstand water and heat stress under rainfed conditions.
Objectives: This systematic review synthesizes empirical evidence from 2008–2024 to characterize the biosynthetic pathways, intracellular compartmentalization, and protective mechanisms of the five canonical osmoprotectant groups, and to evaluate their agronomic efficacy across wheat, maize, coarse cereals, and oilseed crops under field and controlled-environment conditions.
Critical Synthesis: Osmoprotectants — encompassing amino acids (proline, glycine), quaternary ammonium compounds (glycine betaine), tertiary sulphonium compounds (dimethylsulphoniopropionate), soluble sugars (trehalose, sucrose), and polyhydric alcohols (mannitol, pinitol) — operate through convergent physiological axes: osmotic adjustment, membrane lipid bilayer stabilization via preferential exclusion, antioxidant enzyme upregulation, and transcriptional modulation of heat- and drought-responsive gene networks. Foliar-delivered proline at 20–50 mM increased wheat grain yield by 2.88–52.88% under graduated drought intensities [15]. Salicylic acid at 100 ppm augmented maize grain yield by 78.8% over drought-stressed controls at the vegetative stage, while also enhancing relative water content and membrane stability index [29] Glycine betaine mitigated heavy-metal-coupled oxidative stress in wheat through antioxidant enzyme gene activation [14]; Sharma et al., 2024).
Agronomic Implications: Stage-specific foliar application — calibrated to vegetative rather than terminal-reproductive windows — maximizes protective efficacy. Integration of nano-formulated osmoprotectants (SNP-NP at 90 ppm) with salicylic acid represents a scalable frontier for semi-arid dryland production systems. Systemic adoption of osmoprotectant spray protocols within the rainfed crop calendar could yield 20–40% water savings while sustaining productivity benchmarks.