Assesment of genetic diversity and relationships among maize inbred lines developed in Italy

The genetic diversity pattern of a sample of 144 maize inbred lines comprising 106 Italian entries, considered representative of the breeding material developed at the Bergamo Maize Breeding Station, and a sample of 38, mainly US Corn Belt based, reference lines was accessed using AFLP markers. A total of 811 polymorphic fragments were identified. Exploration of the variation disclosed by the lines by means of principal component analysis (PCA) and hierarchical clustering allowed their division into major heterotic groups. The obtained grouping of the inbred lines reflected pedigree information and resulted in the identification of major clusters derived from Lancaster Sure Crop (LSC), Iowa Stiff Stock Synthetic (BSSS), and miscellaneous heterotic breeding material. AMOVA statistics, performed on the established genetic structure, revealed a high proportion of variance between individuals and among populations stressing the high polymorphic nature of the maize pool analyzed. Regarding population structures, the genetic distance among populations (FST = 0.50 } 0.1) and the degree of inbreeding within groups (FSC = 0.46 } 0.1) did not diverge significantly, while both significantly differed from the degree of relatedness between markers within groups (FCT = 0.06 } 0.04). In conclusion, the results presented indicate that AFLPs are useful in assigning inbred lines to heterotic groups and for superior line development with the aim to maximize heterosis and consequently yield performance.