IDENTIFICATION OF QTL FOR GRAIN-YIELD IN AN ELITE HYBRID OF MAIZE - REPEATABILITY OF MAP POSITION AND EFFECTS IN INDEPENDENT SAMPLES DERIVED FROM THE SAME POPULATION

Little information is presently available on the repeatability of QTL identification across different samples and different environments. In previous experiments we identified QTL for grain yield and other agro nomic traits in 232 F3 families derived from the cross B73xA7, in test cross combinations with two inbred lines. An independent dent sample o f 55 F3 families, drawn from the same population, was analysed for gra in yield. Segregating progenies were evaluated in testcrosses and geno typed using 110 RFLP markers. Three major QTL have been identified. Tw o of them showed map positions, direction and magnitude of effects fai rly consistent with those detected in the previous experiments and the third mapped in a genomic region previously nor investigated with mol ecular markers. Two QTL identified in the first sample remained undete cted. The effects of small sample size, sampling bias and environmenta l variation on QTL identification are discussed.