JOINT SEGREGATION OF ALLOZYMES IN CATFISH GENETIC CROSSES - DESIGNATION OF ICTALURUS-PUNCTATUS LINKAGE GROUP-I

Polymorphic isozymes visualized by starch gel electrophoresis and hist ochemical staining were examined in parents and 1,000 progeny of 24 si ngle-pair matings of channel catfish Ictalurus punctatus and three int erspecific crosses of channel catfish x blue catfish I. furcatus. Poly morphic loci that could be scored from fin tissue included aconitate h ydratase (mAH()), glucose-6-phosphate isomerase (GPI-B-*), glutathion e reductase (GR()), phosphoglucomutase (PGM(*)), and UDPglucose-hexos e-1-phosphate uridylyltransferase (UGHUT-2()). Inheritance of observe d electrophoretic variation was consistent with Mendelian segregation of codominant alleles in progeny selected randomly from the individual crosses. Although mAH(), GPI-B-*, PGM(*), and UGHUT-2(*) appeared to assort independently within the limits of the data, strong evidence f or linkage of GR() and PGM(*) was obtained (19.7% recombination, P le ss than or equal to 0.001 for data combined from two informative pedig rees); this linkage was designated Ictalurus punctatus linkage group I . This study represented a first step in assembly of a catfish gene ma p large enough to provide genetic markers for each catfish chromosome to enable detection of specific loci associated with traits of economi c importance by genetic linkage analyses. For the polymorphic loci stu died here, no consistent association of genotype with average body wei ght was observed.