Vol. 9, Special Issue 12, Part H (2025)

Maize (Zea mays L.) is an important fodder crop, and enhancing biomass yield, leaf area and overall forage quality requires systematic use of the genetic diversity available in global germplasm resources. In this study, the CIMMYT Asia Association Mapping (CAAM) panel was evaluated during two contrasting seasons, rabi 2023 (249 genotypes) and kharif 2024 (200 genotypes), to quantify phenotypic variability in fodder yield and related traits using k-means clustering. The panel was phenotyped under an alpha-lattice design for key phenological, morphological and biomass parameters. Across both seasons, k-means consistently grouped genotypes into six clusters, but composition of clusters during both the seasons are different, hence clustering of individual seasons is presented revealing a stable yet environmentally responsive structure of diversity, with clear shifts in cluster membership and trait expression reflecting genotype × season interactions. Distinct ideotypes were identified in each season. During rabi 2023, cluster 2 recorded the highest biomass with a green fodder yield of 26,941 kg ha⁻¹ and a dry fodder yield of 9,579 kg ha⁻¹, supported by superior plant height and leaf area. In kharif 2024, cluster 3 emerged as the most productive group, achieving a green fodder yield of 38,462 kg ha⁻¹, while clusters 1 and 5 also expressed strong leafiness and high biomass potential. Inter-cluster distances were substantially greater than intra-cluster distances in both seasons, confirming meaningful divergence among clusters and highlighting clusters 1, 2 and 3 as promising parental pools for creating wide and complementary heterotic combinations. The two-season analysis clearly demonstrates the presence of well-structured and exploitable phenotypic variation in the CAAM panel. The identification of stable high-performing clusters, along with season-specific divergent groups, provides a robust foundation for cluster-based parent selection and for designing targeted breeding strategies aimed at developing high-yielding, leafier and environmentally resilient fodder maize cultivars.