PLANT CELL BIOTECHNOLOGY AND MOLECULAR BIOLOGY

Maize (Zea mays L.) is one of the most genetically diverse cereal crops and an important source of quality green fodder owing to its high biomass potential and adaptability across environments. With increasing pressure on livestock systems to supply nutritionally superior fodder under changing climatic conditions, the identification and utilization of genetically diverse germplasm for fodder improvement has become imperative. The present study was undertaken to characterize genetic diversity and trait interrelationships for fodder-related traits in maize using multivariate analysis. A diverse set of tropical and subtropical maize accessions from the CIMMYT Asia Association Mapping (CAAM) panel was evaluated during two contrasting seasons, Rabi 2023 and Kharif 2024, in an alpha lattice design with two replications. A total of 249 and 200 genotypes were assessed across seasons for green fodder yield and key phenological, morphological and biomass-associated traits. Principal component analysis (PCA) was performed on standardized trait data, and principal components with eigenvalues greater than one were interpreted to identify major sources of variation and stable trait groupings. Across both seasons, PCA revealed a consistent and biologically meaningful structure of variation. The first four principal components in Rabi 2023 and the first five in Kharif 2024 together explained over 74% of the total phenotypic variability. In both environments, the first principal component was predominantly driven by vegetative biomass traits, including leaf area per plant, leaf length, leaf width, plant height, number of leaves and fodder yield components, indicating that canopy development and overall plant vigour constitute the primary axis of genetic divergence for fodder productivity. The second principal component was consistently governed by flowering traits, particularly days to 50% tasseling and silking, forming an independent phenological axis largely unrelated to biomass accumulation. Secondary traits such as stem diameter and leaf ratio contributed to higher-order components, reflecting finer differentiation among genotypes. PCA biplot analysis further confirmed stable clustering of genotypes along biomass- and phenology-driven axes across seasons, with minimal seasonal shifts in genotype positioning, suggesting a strong genetic control of major fodder traits and limited genotype × environment interaction. The clear separation of canopy-related traits from flowering behaviour indicates that fodder yield improvement can be achieved without adversely affecting crop maturity. Overall, the study demonstrates substantial genetic diversity within the CAAM maize germplasm and identifies robust, seasonally stable trait combinations governing fodder yield. The results provide a strong multivariate basis for parental selection, heterotic grouping and ideotype development aimed at enhancing biomass yield and forage quality in maize breeding programmes.