Gene Mapping,lsolation and Genetic Improvement in Catfish

( Book Chapter ) Aquatic Genomics – Steps Toward a Great Future
45 – 60
Dunham, Rex;Liu, Zhanjiang
Pub ID:
The catfish genetic improvement program at Auburn University utilizes an integrated approach of genomics, gene isolation, selective breeding and gene transfer for the development of superior lines, crosses, hybrids and transgenics of catfish. A linkage map was recently completed that identified 44 linkage groups containing 607 AFLP markers. Analysis and placement of 100 microsatellite loci will soon he completed and added to this map as well as several quantitative trait loci. Additionally, 17 isozyme loci weremapped to 5 linkage groups. Selective genotyping has identified 3 microsatellites linked to feed conversion efficiency in channel
catfish, lctalurus punctarus, one microsatellite linked to growth and one microsatellite putatively linked to resistance to the bacterium, Edwardsiella ictaluri. F(ST) analysis indicated that nine of 13 isozyme loci examined in channel catfish were linked or associated with increased growth rate. Our laboratory has sequenced 7,000 EST clones from muscle, pituitary, brain, head
kidney, skin and spleen of channel catfish representing 4,000 different genes.cDNA microarray analysis illustrated differential gene expression during hormone induced ovulation and in the muscles of different aged fish. Selection,
intraspecific crossbreeding, interspecific hybridization and genetic engineering were all successful for improving production traits in catfish. Growth hormone gene transfer and transfer of lytic peptides increased the growth and bacterial disease resistance, respectively, for channel catfish. Interspecific hybridization
actually improved more traits in a single cross than any of the other breeding programs. However, mass selection combined with crossbreeding,
mass selection combined with genetic engineering or strain selection combined with hybridization resulted in more genetic enhancement than any
of the genetic improvement programs individually. The best aquaculture genotypes for the future will be developed by utilizing multiple breeding
programs. The gene mapping data, QTL data, gene isolation and general genomics resenrch will be utilized and integrated for marker-assisted
selection , genetic engineering and in combination with multiple genetic improvement programs to maximize genetic potential of catfish for commercial catfish culture.
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