Construction of large advanced crop

Construction of large advanced crop populations can be both time consuming and expensive. Therefore, large populations of F2s, backcrosses (BC) such as BC1s, or other early generation crosses, combined with high through-put genotyping method provide an alternative. Vales et al. [13] estimated the effect of population size on QTL mapping and concluded that a large early generation population was able to detect more QTL, including small-effect QTL, than studies that used smaller advanced generation populations. A huge maize-teosinte BC1population of 1749 individuals was constructed for fine mapping of QTL associated with domestication, and resulted in identification of hundreds of QTL for 22 traits [14]. When the marker density was increased in the region of the tb1 gene, the authors were able to detect additional crossovers in the open reading frame (ORF) and flanking regions, indicating the importance of both population size and marker density for QTL cloning.