Master of Science (MS)


Renewable Natural Resources

Document Type



Genetic effects influencing salinity tolerance (ST) and cold tolerance (CT) were evaluated in two full diallel mating designs using six tilapia varieties: Oreochromis aureus (BL), O. mossambicus (MO), O. niloticus (NI), O. niloticus crossbreds (RE), Mississippi commercial strain (MC) and Florida red tilapia (FL). Statistical analyses provided estimates of direct heterosis (hi), cross heterosis (hij), maternal effects (mi), line effects (li), reciprocal and specific reciprocal effects (rij and r**ij), and general and specific combining abilities (GCA and Sij). Analysis of genetic effects for ST indicated that FL exhibited significant GCA (P < 0.01). BL, FL, and MO exhibited highly significant li (P < 0.01). Highly significant mi (P < 0.01) was apparent for FL and RE. Highly significant Sij and hij% (P < 0.01) were exhibited in two and eight variety combinations (VCs), respectively. Highly significant rij (P < 0.01) was observed in BL-MO, and MC-RE. In addition, highly significant r**ij (P < 0.05) was noted in BL-MO and FL-RE. Analysis of genetic effects for CT indicated that BL, MC and RE exhibited significant GCA's (P < 0.05). Highly significant li and mi (P < 0.01) were apparent in BL and RE, respectively. Significantly negative Sij (P < 0.05) was exhibited only in BLxMC, while negative and significant hij% (P < 0.05) was apparent in BLxMC, FLxMO and FLxRE. Highly significant rij (P < 0.01) was apparent in FL-MC and MC-RE, while negative and significant r**ij (P < 0.05) was exhibited only in FL-MC. No significant direct heterosis (hi) was apparent in ST or CT. Improvement in ST in could be accomplished by developing a breeding program combining selection, hybridization and backcrossing in MO, BL and FL, while improvement of CT may be accomplished by selection and hybridization in BL. The potential environmental and commercial implications of developing salinity-tolerant and cold-tolerant tilapia varieties and crosses are discussed.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

C. Greg Lutz