Genetic Variation for Autumn–Winter Forage Yield in a Segre-gating Tetraploid F1 Population of Paspalum notatum

Autumn-winter forage scarcity limits subtropical livestock systems. This study aimed to: (1) develop a segregating F₁ population derived from parents contrasting in autumn-winter biomass yield (WBY) in tetraploid Paspalum notatum; (2) estimate phenotypic and genetic variability for WBY across environments; (3) determine the relationship between WBY and spring-summer biomass yield (SBY); and (4) assess the feasibility of UAV-derived vegetation indices as non-destructive estimators of dry autumn-winter biomass yield (WBY) for future breeding. A population of 182 tetraploid F1 hybrids was evaluated at two sites in Corrientes Province, Argentina (2022-2024). WBY exhibited wide genotypic variability across locations and years (p < 0.001), with significant effects of genotype, location, and genotype × location interaction. Broad-sense heritability (H²) ranged from 0.41 to 0.64, reflecting sensitivity to thermal and moisture conditions of each environment. WBY showed a positive, moderate association with SBY (R² = 0.20 - 0.26), indicating that selection for cool-season yield does not compromise summer productivity. Among the indices evaluated, the Normalized Difference Red Edge Index (NDRE) was the most robust predictor of WBY (R² up to 0.67), though predictive accuracy varied with environmental conditions. Overall, the results demonstrate substantial and exploitable genetic variation for cool-season forage yield in P. notatum.