Constitution of association panel of tropical field corn (Zea mays L.) for kernel and cob-related traits

Maize is one of the model crops for genetic study and has wider variability for yield component traits. Capturing the available variability and utilizing it in the breeding program is a prerequisite of the maize improvement program. On the other hand, the energy and resources required to characterize the germplasm are huge and maintenance of the trait becomes challenging when the population size of the germplasm is large. However, based on the concept of a mini-core collection, the breeder can capture maximum variability by sampling the entire germplasm available and utilizing them in an active crop improvement program. There is limited information on the formulation of the subset that captures maximum variability in India. Until now we had no mini core collection of field corn constituted for using them in strategic research and breeding, albeit having a large number of populations and derived lines with enormous variability. Hence, the study aimed to constitute a specific trait-specific association panel named ‘Field Corn Panel of IARI’ to capture all the possible variability in our germplasm base for kernel and cob-related traits. For this purpose, 514 germplasm lines derived from 12 diverse source populations were evaluated in augmented design during kharif 2020 at ICAR-IARI, New Delhi. The principle component analysis (PCA) on this germplasm indicated that Kernel row number, Kernel number per row, Cob Length, Cob Diameter, and Shelling Percentage (%) were important determinants for diversity in field corn. Hence, the germplasm characterized for these traits was subjected to Core Hunter 3.0 to derive the subset named ‘Field Corn Panel of IARI’ comprising 200 genotypes. The comparison of this panel with the larger germplasm set (514 genotypes) using statistical tools revealed non-significant differences in the descriptive parameters for the traits under consideration. The simple sequence repeat (SSR) marker-based diversity analysis indicated that the constituted panel contained diverse genotypes that captured the same variation as that in the larger germplasm set. This trait-specific panel would serve as the base research material for genome.wide association study (GWAS), genomic prediction, and identification of tolerant inbred lines for biotic and abiotic stresses and yield component traits in field corn.