Ionomic and metabolic signatures governing sterility mosaic disease resistance in pigeonpea

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Introduction Sterility mosaic disease (SMD) represents a critical biotic constraint that severely limits pigeonpea yields throughout South Asia. The disease is incited by Pigeonpea sterility mosaic emaravirus (PPSMV), which is actively transmitted by the eriophyid mite vector Aceria cajani . Methods Host-pathogen interactions were comprehensively analyzed using a multi-disciplinary approach. This included field screening, molecular and microscopic diagnostics along with biochemical, spectroscopic and elemental profiling. Results Over two growing seasons, genotypes ICPL 20096-1 and ICPL 99090 exhibited high resistance, while the susceptible check (ICP 8863) exceeded 90% disease incidence. Molecular analysis confirmed PPSMV-2 as a geographically related strain of Emaravirus toordali and Emaravirus cajani . SEM revealed severe trichome deformities and collapsed stomatal guard cells in infected leaves. Biochemically, advanced disease infection increased stress injury, phenol content, peroxidase and polyphenol oxidase activities while depleting chlorophyll and soluble sugars. This reflects triggered progressive physiological impairment and active biochemical defenses. Fourier Transform Infrared Spectroscopy (FTIR) analyses revealed prominent shifts in protein, lipid and polysaccharide spectral bands (N-H, C-H, C=O, C-O-C stretching) which tentatively point to membrane damage and modified primary metabolic state following infection. Concurrently, Inductively Coupled Plasma Mass Spectrometry (ICP-MS) data demonstrated a noticeable reduction in tissue concentrations of Na, Mg, Al and K. This elemental depletion included a drop in calcium levels that may have altered downstream calcium signaling pathways and cellular structural integrity accompanied by decreased manganese concentrations that suggest a potential inhibition of manganese-activated enzymes required for carbohydrate metabolism. Discussion Collectively, these baseline findings identify candidate spectral and mineral biomarkers unique to resistant genotypes while reinforcing the genetic dominance of PPSMV-2. This exploratory profile of SMD associated elemental and spectral shifts serves as a template for validating resistance traits across a wider range of pigeonpea genotypes.

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