04189cas|a2200409 a 4500 20260818115030.0 021226s2000 th uu|m rtt 0| a1engxd .b11872093 AIT Thesis no. AQ-00-26 Goel, Amit Kumar Genetic characterization of Clariid catfish (Clarias Macrocephalus) and its hybrid (female Clarias macrocephalus X male Clarias gariepinus) in Thailand Bangkok : Asian Institute of Technology, 2000 50 leaves Thesis ; no. AQ-00-26 A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Environment, Resources and Development Thesis (M. Sc.) - Asian Institute of Technology, 2000 The culture of hybrid catfish, the hybrid between the native female Clarias macrocephalus and the exotic male Clarias gariepinus, is currently one of the fastest growing sectors of aquaculture in Thailand. The rapid expansion of hybrid catfish culture has also led to concerns about its impacts on genetic diversity of other species and on natural and pure stocks of Clariidae. It is possible that the F 1 hybrid can successfully be used as broodstock for the production of later generation and/or backcross hybrids that may lead to hybrid introgression and loss of unique F 1 hybrid genotypes. This has implication for both aquaculture (through the loss of the desired characteristics of the F 1 hybrid) and for wild populations of the indigenous catfish, which may become introgressed. Allozyme study had indicated that some introgression of C. macrocephalus stocks might be occurring (Chaiparinya 1996). However, DNA markers can be more reliable and informative and involve simpler sampling protocols. Therefore, the nuclear genome was analysed using the nuclear DNA marker, CH4 exon and an alternative marker using restriction fragment length polymorphism (RFLP) of the ND 516 portion of the mitochondrial DNA was also developed. This study suggested that possession of double banded genotype in nmthern population of C. macrocephalus, from Nan, might be an indicative of C. gariepinus introgression. However, other factors, such as non-specific amplification, might be causative of occurrence of double-banded pattern in C. macrocephalus. Elsewhere, C. macrocephalus populations populating the other regions of Thailand did not show any sign of C. gariepinus fixed double banded genotype. These findings suggest that the hybrid introgression be in its early stage. However, if situation persists, ceaseless introgressive hybridization may be deleterious to existing genetic resources of the Clariidae in Thailand. These results also suggest that for introgression studies the use of mitochondrial DNA marker is not very useful especially when only one way hybridization is going on and introgression is not extensive. However, an appropriate nuclear DNA marker(s) coupled with indigenous knowledge and an informed sampling strategy will enable a full understanding of the introgression issue in Clariidae in Thailand. Catfishes Genetics Thailand Hybridization Mair, G.C., Chairperson Macaranas, Julie M., Chairperson Stevens, Willem Frans, Examination Committee Bart, Amrit N., Examination Committee H. M. The Queen of Thailand, Scholarship Donor Asian Institute of Technology. Thesis ; no. AQ-00-26 Full-Text http://203.159.5.9/ait-thesis/detail.php?q=B07177 .b11872093 mnait u 240403 0 021226 m a u 0 mnait mnarc 20 40 Barcode : 30050120696785 CREATED : 2001-07-29 RECORD # : i12310840 LPATRON : 1017164 LCHKIN : 2005-10-22 # RENEWALS : 0 # OVERDUE : 0 IUSE3 : 0 TOT CHKOUT : 2 TOT RENEW : 1 Barcode : 30050120357818 CREATED : 2016-08-06 RECORD # : i13024188 LPATRON : 0 LCHKIN : - # RENEWALS : 0 # OVERDUE : 0 IUSE3 : 0 TOT CHKOUT : 0 TOT RENEW : 0 49452 49452 0 0 0 0 MAIN MAIN mnait 2026-08-18 50.00 0 AIT Thesis no. AQ-00-26 30050120696785 2026-08-18 11:50:30 2 2026-08-18 20 0 0 0 0 MAIN MAIN mnarc 2026-08-18 0 AIT Thesis no. AQ-00-26 30050120357818 2026-08-18 11:50:30 1 2026-08-18 40