Genotype by environment interaction and dry matter yield stability of Guinea grass (Panicum maximum Jacq.) genotypes in Western Oromia, Ethiopia

Screening different germplasm and landrace collections of high-yielding forage crops improves feed availability and quality, addressing deficits in livestock production. The study was conducted to evaluate and identify high-yielding and stable Guinea grass (Panicum maximum Jacq.) genotypes for herbage yield, nutritional quality, and agronomic traits. Ten Guinea grass genotypes and one standard check variety (Degun guziya) were tested in randomized complete block design with three replications, using 5.4 m² plot area and 0.3 m row spacing. Seeds were sown at 10 kg/ha, with fertilizer application rates of 100 kg/ha NPS and 50 kg/ha urea. Agronomic traits, yields, and stability were measured and analyzed. Analysis of variance showed significant (p < 0.01) variations among genotypes, environments, and years for the number of leaves per plant (NLPP), herbage dry matter yield (HDMY), and seed yield. Genotype by environment (G × E) interactions significantly influenced NTPP and seed yield. Additionally, NLPP, leaf to steam ratio, HDMY, and seed yield were affected by genotype × environment × year interactions. Additive main effect and multiplicative interaction analysis indicated significant (p < 0.001) effects of genotype, environment, and G × E interaction, with genotype contributing 42.63% of the total variation, followed by environment (33.84%) and G × E interaction (23.53%). The maximum mean HDMY was recorded for genotype NG-0105 (15.01 t/ha), followed by NG-0104 (13.97 t/ha), across all environments. Stability analysis confirmed that NG-0105 and NG-0104 were the most stable genotypes, exhibiting yield advantages of 40.67 and 30.93%, respectively, over the standard check. Therefore, these genotypes are recommended for cultivation and release as new varieties in the tested environments.