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Browsing by discipline "Kasvintuotannon biologia (kasvinjalostus)"

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  • Aragon Obando, Erwin Manuel (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.
  • Jiménez Caldera, Oswalt Rafael (2009)
    Common bean (Phaseolus vulgaris L.) is one of the most important crops in Nicaraguan agriculture. Bean production is carried out on small scale farms, where farmers generally lack key inputs. Seeds have been identified as the most critical input in bean production. For this reason, national seed program will be a priority during next ten years. Among the four main seed quality components, genetic component has been the least studied. The occurrence of offtype seeds and plants in the cultivar ‘INTA ROJO’ during seed production has hindered the seed certification process and questioned the genetic quality of the cultivars produced in Nicaragua. The present study aimed to compare the genetic composition of different seed categories in the cultivar ‘INTA ROJO’, and to confirm the genetic identity of offtype seeds and plants found in this cultivar. The genotype frequencies of fourty individuals were analyzed using ten microsatellite markers in the following seed categories: Breeder’s seed, foundation seed, registered seed and certified seed. The genotype frequencies were analyzed using Fisher’s exact test, where breeder’s seed was assigned as a reference population. Additionally, twenty offtype seeds and plants, among them the offtype seeds known as “frijol viterra” and “frijol rojo oscuro”, were contrasted with breeder’s seed through pairwise comparisons of genetic distances. The results suggest that changes in genotype frequencies take place during seed production and they are ascribed to the selection pressures caused by environmental differences among production regions and inadequate varietal depuration procedures during seed production. In addition, the offtypes denominated “frijol rojo oscuro” were identified as an unknown cultivar probably derived from natural segregations, mutations and out-crossing among bean seed lots, and in less degree from accidental seed mixtures. In contrast, “frijol viterra” was confirmed to be the same cultivar ‘INTA ROJO’. Its differences in seed weights were associated rather to environmental effects than to genotypic ones. The seed technology implications of these findings and further perspectives are discussed.