A QTL Map for Growth and Morphometric Traits Using a Channel Catfish X Blue Catfish Interspecific Hybrid System
Type of DegreeDissertation
Fisheries and Allied Aquacultures
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Many genetic programs have been designed to enhance performance for different desired traits in ictalurid catfish. Using quantitative trait loci (QTL) analysis, specific culture traits can be identified so that the performance of individuals can be improved using marker assisted selection (MAS). Using a combination of QTL analysis and MAS, overall genetic gain per generation might be increased compared to traditional selection because of the potential for increased intensity and accuracy of selection. The channel catfish, Ictalurus punctatus, and blue catfish, I. furcatus, each have superior traits that could be incorporated into a synthetic breed. For instance, a backcross population offers the potential of a fish with the growth rate of a channel catfish and the body conformation of a blue catfish, possibly increasing dressing percentage per fish. Head length, head depth, head width, body depth, body width, caudal depth, and caudal width, total length, and body weight were measured for 71 backcross full sib individuals. These individuals were genotyped using AFLP analysis and used for construction of a QTL map. The nine traits were strongly correlated (P= 0.05). As expected the morphometric traits have minimal variation while body weight and total length had large components of variation. For all seven morphometric traits and two growth traits, 9 of 44 linkage groups had at least one significant QTL (P=0.05) and 12 of 44 at P= 0.10. Linkage group 19 was unique as it had multiple QTLs for every trait measured, except for caudal width for which no QTL was indentified on any linkage group. Caudal depth is represented on the map by the fewest linkage groups, being significant (P= 0.05) in two groups. Approximately, half of the markers measured were associated with positive effects on the traits and half had negative effects. Linkage groups 5, 7, 9, 39, and 40 were significant for multiple traits and always had a trait negative effect. Total length is represented on the map by the most linkage groups and the most markers. The linkage relationships found among body weight, total length and the 7 morphometric traits indicated that multiple trait MAS to increase body weight, body depth, body width and caudal depth while decreasing the other traits measured body weight and carcass yield simultaneously might be difficult. Certain QTLs seemed more promising for accomplishing the goal, and focusing on MAS on these markers might yield positive results.