In figure 19-16, the congenic lines are shown. These are the lines that are identical except for a small area of concern. It is the QTL region. The genes which control the complex traits or variation in quantitative traits are called quantitative trait loci (QTL).
In the congenic lines, the red color indicates Beef-master genotype and the yellow color indicates Sun-gold genotype.
The average fruit weight is more in lines 1, 6, 7, 8, and 9. They are line 1- 181.4 g, line 6 -182.2 g, line 7- 180.6 g, line 8 -180.7 g, and line 9-181.8 g. These lines have a Beef-master chromosome segment, which has ald2.
Other lines such as 2, 3, 4, 5, and 10 are with Sun-gold allele of the gene ald2. They have less fruit weight. No other gene is associated with fruit weight as gene ald2.
From the above results we can know that ald2 gene is the gene behind this QTL.