Gamba grass (Andropogon gayanus Kunth) is a promising forage alternative for Brazil’s Cerrado regions, attracting increasing research interest due to its potential to complement or replace widely planted species such as Urochloa and Megathyrsus. Despite the release of three cultivars, significant improvements in dry matter (DM) yield and forage quality are needed to fully realize its agronomic potential. This study aimed to evaluate genetic variability, estimate narrow sense heritability, and predict expected genetic gains for DM yield and key forage quality traits in two gamba grass populations derived from the cultivars BRS Sarandi and Planaltina. Trials were established in spring 2017 in Planaltina, DF, and evaluated during February–March 2018 and January–March 2019. Crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), cellulose (CEL), and hemicellulose (HEMIC) were quantified alongside DM yield. BRS Sarandi exhibited higher CP (12.3% vs. 9.8%) and lower NDF (57.1% vs. 63.4%), ADF (36.2% vs. 41.5%), CEL (20.8% vs. 23.7%), and HEMIC (20.9% vs. 21.9%) compared to Planaltina, while DM yield did not differ significantly between populations (4.57 t·ha⁻¹ vs. 4.50 t·ha⁻¹ per harvest, p > 0.05). Heritability estimates for individual harvests ranged from 0.31 to 0.68 for DM yield and 0.28 to 0.62 for quality traits, whereas multi-harvest models across years yielded lower estimates (0.07–0.27). Expected annual genetic gains were modest, with the highest predicted increase for CP (0.45% per year) and the largest decrease for NDF (−0.78% per year), reflecting the quantitative nature of trait inheritance and strong environmental influence. This study provides novel insights by simultaneously comparing two populations for multiple harvests and quantifying both yield and detailed forage quality traits, offering practical guidance for gamba grass breeding strategies. Results indicate that breeding programs should prioritize multiple selection cycles, precise phenotyping, genotypic and potentially genomic selection to accelerate improvement in both DM yield and forage quality, overcoming the constraints of low heritability and multi-trait selection.

Gamba grass, a leading alternative for forage development in Brazil Cerrado’s areas, has received a more extensive researchers' attention in the recent years. Although three cultivars were already released, for gamba grass to be an alternative to most planted forage species in Brazil (Genera Urochloa and Megathyrsus), significant technological improvements need to be achieved, mainly in genetic development of DM yield and forage quality. Understanding genetic variability of populations and the nature of the gene action governing the inheritance of traits are important contexts to obtain genetic gains from selection in breeding programs. The objective was to estimate DM yield and quality traits narrow-sense heritability and expected gains from HS family tests of two populations originated from the cultivars BRS Sarandi and cv. Planaltina. The trials were established in spring 2017 in Planaltina, DF and evaluated in February and March, 2018 and January, February, and March, 2019. Cultivar BRS Sarandi presented better forage quality than did cv. Planaltina due to higher CP and lower NDF, ADF, CEL, and HEMIC contents, and they did not differ for DM yield. Heritability estimates were low to moderate in magnitude for both populations, ranging from 0.31 to 0.68 for individual harvests and from 0.07 to 0.27 for models across harvests and years. Similar low h2 magnitudes across harvests and years were also observed for all quality traits estimated for both populations. The theoretical expected gains per year for all traits reflected modest gains, but all aligned with those from literature. The nature of the genetic variation is quantitative for all studied traits, since they were highly influenced by the environment. Results suggest more elaborated breeding methods, more cycles of selection, and more accurate measurement techniques to improve chances of success when breeding gamba grass for yield and quality. Alternatively, the use of genomic selection may promote a faster improvement of DM yield and forage quality traits, to overcome the constraints of low heritability, number of selection cycles, high costs, and multi-trait selection.