Investigating the Impact of Tillering on Yield and Yield-Related Traits in European Rice Cultivars

Optimizing rice productivity is crucial for global food security, especially in Mediterranean environments. This study investigated the influence of tillering capacity on yield and other agronomic traits in nine European rice cultivars over two seasons (2021–2022). A split-plot design was used with cultivars as the main factor and five tillering levels: main stems (Mn), primary (T1), secondary (T2), tertiary (T3), and quaternary (T4) as sub-factors. The grain yield, total dry matter, harvest index, 1000-grain weight, and number of stems were measured. Significant differences were revealed among cultivars, tillering levels, and their interaction for all traits. Mn and T1 consistently outyielded later tillers, with Ronaldo’s Mn achieving 4.71 t ha−1. Mare and Olympiada displayed the highest average yields (1.52 t ha−1) through balanced resource allocation across tillers. Strong correlations between tillering levels and yield (R2 = 0.73) demonstrate that early tillers significantly enhance productivity. We conclude that optimizing early tiller productivity—rather than maximizing tiller numbers—should be prioritized in breeding programs. Cultivars combining vigorous Mn and T1 development with efficient resource partitioning offer the most promising approach for improving Mediterranean rice productivity.