QTL analysis for yield and thousand grain weight. Genome-wide QTL analyses for yield (red) and thousand grain weight (blue) in the Spark x Rialto DH population, across five environments (Norwich UK, Sandringham UK, Scotland, France, Germany) and in three years (2001, 2002 and 2003). The threshold value for significance is set at 2.5 LOD. Consistent, significant effects for both yield and thousand grain weight were observed on chromosomes 4D (Rht-D1) and 6A. Inset: the box and whisker plot exhibits the percentage difference between DH lines fixed for the QTL region on chromosome 6A, with the median and mean denoted by the black and yellow line, respectively.