RT-qPCR analysis of genotype-specific beet yellows virus accumulation in sugar beet

Background: Rapid and objective characterisation of viral accumulation requires methods combining fast detection and temporal resolution. Aims: Develop a two-phase approach for screening sugar beet genotypes for beet yellows virus (BYV) accumulation dynamics. Methods: Phase 1 employed one-enzyme RTX-PCR for rapid BYV detection, followed by single-time-point RT-qPCR at 30 days post-inoculation (dpi) to screen ten genotypes. Phase 2 performed time-course RT-qPCR at six time points (10-60 dpi) on two contrasting genotypes selected from Phase 1, with assay performance validated by a standard curve. Results: One-enzyme RTX-PCR confirmed BYV infection, enabling quantification; single-time-point RT-qPCR at 30 dpi showed a 5.7-fold titre range (5.6 × 107 to 3.2 × 108 copies), while time-course RT-qPCR revealed distinct trajectories, relatively resistant GZs1 increased gradually (~5.0 × 105 at 10 dpi to 1.7 - 2.3 × 107 at 40 - 60 dpi) whereas susceptible Masaryk rose rapidly early (~3.1 × 106 at 10 dpi) and peaked at 3.7 × 107 by 40 dpi, dynamics not captured by single-time-point measurements; standard curve metrics indicated high assay quality (R2 = 0.9976; efficiency = 103%). Conclusions: This two-phase method combines speed with precision for effective genotype comparison. It reveals BYV accumulation dynamics that are not captured by single‑point assays.