The six markers used in the second experiment covered 69 Kosambi cM of linkagegroup 23.
The regression interval mapping located the QTL for standard length 14 cM along the linkage group (P < 0.01), for body weight 16 cM along the linkage group (P < 0.05), and for cold tolerance 38 cM along the linkage group (P < 0.05) (Fig. 1).
The marker with the highest association with body weight and standard length was UNH130 (Table 2), with significance levels of P= 0.002 and P= 0.014, respectively.
The average weight and length of fish homozygous to the paternal allele were 0.4 standard deviation above the population average, while heterozygous fish were 0.2 standard deviation below it, for both traits (Table 3). The regression interval mapping analysis revealed additive effects of 9.2 mm and 2.8 g and dominant effects of 26.1 mm and 12.5 g, indicating a decreasing overdominance effect for both traits (Table 4).
No marker was associated with the ratio body weight/standard length. As expected, a high correlation between body weight and standard length was observed (R2 = 0.91, P < 0.0001).
In the analysis of the canonical variables, only one variable was associated with the marker UNH130, indicating that the same locus affects both body weight and standard length. There was no correlation between these two traits and cold tolerance.