Yield Stability and Grain Yield Performance of Proso Millet (Panicum miliaceum L.) Genotypes Across Contrasting Years in Northern Kazakhstan

Proso millet (Panicum miliaceum L.) is a drought-tolerant cereal crop with considerable potential for dry-steppe agriculture. This study evaluated grain yield performance and stability of 104 proso millet genotypes originating from 21 countries under climatic conditions in Northern Kazakhstan during 2022–2024. Field experiments were conducted under rainfed conditions using a randomized complete block design with three replications. Grain yield data were analyzed using analysis of variance (ANOVA), additive main effects and multiplicative interaction (AMMI) analysis, genotype plus genotype-by-environment (GGE) biplot analysis, and the stress tolerance index (STI). The study years differed substantially in weather conditions, ranging from severe drought in 2023 (HTC = 0.495) to excessive moisture availability in 2024 (HTC = 4.245). Mean grain yield varied from 2.58 t ha−1 in 2022 to 4.18 t ha−1 in 2024, demonstrating the high productive potential of proso millet under Northern Kazakhstan conditions. ANOVA revealed significant effects of genotype and year on grain yield. AMMI and GGE analyses were used to visualize genotype performance patterns and identify promising germplasm. Shortandinskoe 11 and K-2754 combined relatively high grain yield with stable performance, whereas K-2804, K-2724, and K-2291 demonstrated high productivity and elevated STI values. These accessions represent valuable germplasm for breeding programs aimed at improving grain yield, stability, and drought tolerance; however, further multi-location testing is required to confirm the breeding value and stability of the identified accessions under a wider range of environmental conditions.