Browsing by Subject "genetic differentiation"
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(2009)Genetic composition of Theobroma cacao L., including 60 Nicaraguan farmers accessions, was investigated using nine microsatellite (SSR) markers. Fourteen breeders accessions from Experimental Center “El Recreo”, INTA, Nicaragua, two Criollos accession from CATIE, Costa Rica, and two accessions from Ecuador were included as reference material. The average PIC value (0.78) indicated a high power of discrimination for the nine loci used. A total of 155 alleles were detected at the nine loci. The number of alleles per marker ranged from 10 to 22 with a means of 17.22 alleles per locus. A heterozygosity deficiency (HExp < HObs) was registered for all microsatellite loci. The average expected heterozygosity was=0.68 among Nicaraguan farmers accessions. The Analysis of molecular variance (AMOVA) showed a low level of differentiation among populations. The genetic distances determined for the groups of farmers accessions RAAS and Pacifico Sur are closely similar, while a great genetic distance was observed between RAAN and RAAS groups. The cluster analysis presented a strong genetic relation between the Criollo 13 from CATIE and farmers accession MAT0404. The principal component analysis showed that 7 farmers accession from Nicaragua are genetically related with the accessions Criollo 13 and Yucatan from the international accessions. The present study suggested a good possibility to select farmers accessions to be included in breeding programs, especially those accessions related to know Criollo accessions.
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(2020)Arapaima gigas is one of the world’s largest freshwater fishes and it is native to the Amazon region. The species is over-exploited and sustainable long-term conservation strategies are needed to maintain the genetic diversity of the species. The aim of this study was to analyze the genetic diversity of Peruvian Arapaima gigas populations. The microsatellite data was collected as a part of a three-year project by the Regional Government of San Martín (GORESAM) and Finnish Game and Fisheries Research Institute (FGFRI). The data consisted of 15 microsatellite loci and 324 samples from three populations, Iquitos, Paiche, and Pucallpa. The samples for Iquitos and Pucallpa were collected from populations in the Amazon basin. Samples of Paiche were collected from a captive population in a fish farming research center. The average numbers of alleles and genotypes ranged between 1.9-3.3 and 2.5-4.6, respectively. Population Pucallpa showed the highest average level of heterozygosity (0.41), whereas the lowest level was observed in population Iquitos (0.25). There were altogether 13 loci which showed a statistically significant excess of heterozygosity, and nine loci with significant deficiency of heterozygosity across the three populations. The FIS-values were in accordance with most of the significant deviations indicating the excess or deficiency of heterozygosity. The average FIT-value (0.226) indicated a slight increase of homozygotes. Populations Iquitos and Paiche were on a state of Hardy-Weinberg equilibrium, but population Pucallpa showed a statistically significant deviation from the state of equilibrium. The pairwise FST-values ranged between 0.169-0.373, and they indicate that the three studied populations are genetically different. In addition, the values of Nei’s genetic distance (D) and full-pedigree likelihood analysis indicate a genetic differentiation between the populations. The number of migrants (Nm) between the three populations was estimated based on the mean frequency of private alleles (p(1) = 0.085) and the mean sample size (108 individuals). The number of migrants was 0.273 after the correction for sample size. The genetic diversity within and between the Peruvian populations resembles the results obtained in other studies of Arapaima gigas in the Amazon basin. Sustainable fish farming could offer a solution in maintaining the genetic diversity of the species.
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