Phenotypic Characterization Reveals High Extent of Genetic Variation in Maize (Zea mays L.) Landraces of North-Eastern and North-Western Himalayan Regions of India

Maize (Zea mays L.) is an important cereal crop with multiple uses as food, feed, fodder, fuel and biofuel. Phenotypic characterization of newly collected germplasm is essential for selecting genetically diverse lines for maize breeding. We characterized 99 landrace germplasm accessions collected from India's maize diversity hotspots located in North-Eastern Himalayan (NEH) and North-Western Himalayan (NWH) regions using 30 morphological traits. The high extent of phenotypic variation was observed both in plant and ear traits. Landrace accessions displayed desirable traits for earliness and yield contributing traits namely leaf length and width, ear length and width, kernel rows and kernels per row. Very high positive correlations estimated between flowering traits (days to tasseling and silking; r = 0.99) and maturity (0.78), and between plant height and ear height (0.90). However, kernels per row showed significantly negative correlations with flowering traits (-0.42) and maturity (-0.44). Cluster analysis grouped all 99 landrace accessions into eight clusters. Principal component biplot explained 88.24% variation. Boxplot analysis indicated that the maize landrace accessions from NWH region displayed comparatively high phenotypic diversity for plant phenology and architecture traits, while the accessions from NEH region showed the higher variation for tassel branching, ear number, ear width, kernels per row and 100-seed weight. Maize accessions expressed phenotypic variability for all qualitative traits with leaf colour, silk colour and ear shape showing the maximum variation. Shannon-Weaver diversity indices revealed the presence of high phenotypic variation for tassel branching (SDI = 0.99), ear shape, husk cover, ear width, kernel rows (0.95) and kernels per row (0.69). This genepool of landraces off ers prospects for pre-breeding by providing new sources of allelic variation to enrich elite maize germplasm.