ABSTRACT
In this study, microsatellite markers were developed for the genetic linkage mapping and breeding program of the black tiger shrimp Penaeus monodon. A total of 997 unique microsatellite-containing expressed sequence tags (ESTs) were identified from 10 100 EST sequences in the P. monodon EST database. AT-rich microsatellite types were predominant in the EST sequences. Homology searching by the blastn and blastx programs revealed that these 997 ESTs represented 8.6% known gene products, 27.8% hypothetical proteins and 63.6% unknown gene products. Characterization of 50 markers on a panel of 35-48 unrelated shrimp indicated an average number of alleles of 12.6 and an average polymorphic information content of 0.723. These EST microsatellite markers along with 208 other markers (185 amplified fragment length polymorphisms, one exon-primed intron-crossing, six single strand conformation polymorphisms, one single nucleotide polymorphism, 13 non-EST-associated microsatellites and two EST-associated microsatellites) were analysed across the international P. monodon mapping family. A total of 144 new markers were added to the P. monodon maps, including 36 of the microsatellite-containing ESTs. The current P. monodon male and female linkage maps have 47 and 36 linkage groups respectively with coverage across half the P. monodon genome.
Subject(s)
Expressed Sequence Tags , Genetic Linkage , Microsatellite Repeats , Penaeidae/genetics , Polymorphism, Genetic , Animals , Chromosome Mapping , Female , Genetic Markers , MaleABSTRACT
Randomly amplified polymorphic DNA (RAPD) analysis was used to examine genetic variation in wild black tiger shrimp, Penaeus monodon. Specimens were collected from five geographically separated locations (Satun-Trang, Phangnga, and Medan in the Andaman Sea and Chumphon and Trad in the Gulf of Thailand). A total of 100 P. monodon individuals were investigated using seven arbitrarily selected primers. Fifty-eight (72.5%) of eighty reproducible RAPD fragments ranging in size from 200 to 2200 bp were polymorphic. The percentages of polymorphic bands of the five geographic populations investigated varied from 51.5 to 57.7%. The genetic distance between populations and UPGMA dendrograms indicated that the Medan population was genetically different from Thai P. monodon (Dij = 14.976%). Within Thailand, the Satun-Trang P. monodon was separated from the remaining geographic populations with a genetic distance of 2.632%. RAPD analysis in the present study yielded a total of 252 genotypes. A Monte Carlo analysis illustrated geographic heterogeneity in genotype frequencies within this species, suggesting that genetic population structure does exist in this taxon (P < 0.001 for all primers). Signficant differences in genotype frequencies between Thai and Indonesian (Medan) P. monodon were observed (P < 0.0001). Within Thailand, the Andaman Sea P. monodon was significantly different from that of the Gulf of Thailand (P values between 0.0000 and 0.0387), indicating population differentiation between P. monodon from these two main fishery regions of Thailand.
ABSTRACT
Random amplified polymorphic DNA (RAPD) analysis was used to amplify the genome of black tiger prawns (Penaeus monodon) to detect DNA markers and assess the utility of the RAPD method for investigating genetic variation in wild P. monodon in Thailand. A total of 200 ten-base primers were screened, and 84 primers yielded amplification products. Six positive primers that gave highly reproducible RAPD patterns were selected for the analysis of three geographically different samples of Thai P. monodon. A total of 70 reproducible RAPD fragments ranging in size from 200 to 2000 bp were scored, and 40 fragments (57%) were polymorphic. The RAPD analysis of broodstocks from three different locales, Satun-Trang, Trat, and Angsila, revealed different levels of genetic variability among the samples. The percentages of polymorphic bands were 48% and 45% in Satun-Trang and Trat, respectively, suggesting a high genetic variability of the two samples to be used in selective breeding programs. Only 25% polymorphic bands were found in the Angsila sample, indicating the lowest polymorphic level among the three samples examined. Primer 428 detected a RAPD marker that was found only in P. monodon originating from Satun-Trang, suggesting the potential use of this marker as a population-specific marker in this species.
