Graphical Tracking and Quantitative Grading for Quality Assurance of Grafted Tomato Seedlings

In this study, we aimed to establish quantitative growth standards and quality assessment methods for grafted tomato (Solanum lycopersicum L.) seedlings through a comprehensive analysis of developmental patterns across five production cycles. The growth parameters of scion, rootstock, and grafted seedlings were monitored from cotyledon emergence through the shipping stage over 49 d in both spring and autumn seasons. The results revealed that spring production achieved superior growth, with shipping-stage seedlings reaching 18.43 ± 0.34 cm in height, 181.05 ± 6.34 cm² in leaf area, and 10.261 ± 0.432 g in fresh weight compared with the corresponding autumn values of 16.85 ± 0.40 cm, 160.03 ± 4.58 cm², and 8.362 ± 0.214 g. Rootstock consistently outper-formed scion genotypes during early development, with 25% greater leaf area and 30% higher biomass at the pre-grafting stage. Following successful graft union, exponential growth acceleration occurred between 35 and 49 d after sowing, with the leaf area increasing 3.6-fold and fresh weight increasing 3.5-fold. A novel graphical tracking system was developed to visualize temporal growth patterns across seven key parameters, establishing standard ranges based on mean values ±1 standard deviation (SD). A five-point quality grading system was introduced, assigning scores based on deviation from mean values, with measurements within ±0.5 SD receiving the highest score. This integrated approach provides objective benchmarks for commercial nursery operations, enabling standardized quality assessment and timely environmental adjustments throughout the tomato production cycle. The established standards represent critical tools for optimizing the production of grafted tomato transplants and ensuring consistent seedling quality across different growth conditions.