Análises citogenéticas aplicadas à identificação de haploides e haploides duplos em milho
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| Autor Principal: | |
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| Data de Publicación: | 2021 |
| Formato: | Bachelor thesis |
| Idioma: | por |
| Fonte: | Repositório Comum do Brasil - Deposita |
| Download full: | https://deposita.ibict.br/handle/deposita/679 |
Summary: | Double haploids (DH) are genotypes resulting from haploid induction and subsequent genomic duplication. This technique is of great agronomic interest, as it allows for a reduction in the time to obtain inbreds and the achievement of 100% of the homozygosity of the genotypes, which improves and speeds up the process of obtaining inbred lines and hybrids. However, the methodologies for obtaining and identifying haploids (H) and DH are not always efficient. Thus, this study examined 8 possible genotypes of corn H and DH: 1700345, 1700346, 1700347, 1700348, 1700349, 1700350, 1700351, 1700352, in order to confirm their ploidy levels, validating the methodology for obtaining and identifying the H and DH, and verify the meiotic stability of the possible DH material. To count the chromosome number of H, slides were prepared using root tips with mitotic blockage made by a 19:1 solution of 8-hydroxyquinone 300ppm and cycloheximide 23ppm and staining via the Feulgen method. To verify ploidy, meiotic phase regularity, recombination index (RI), meiotic index (MI) and pollen viability (VP) of DH, slides were prepared using the squash technique, stained using acetic carmine 2% for meiotic analysis and Alexander’s solution for VP. Of the 8 H analyzed, 7 presented 100% of the metaphases with 20 chromosomes, configuring themselves as diploids and 1, H1700349, presented 10% of the metaphases with 10 chromosomes and 90% with 20, configuring themselves as H and diploids. Meiotic analyses showed that all 8 DH had 10 bivalents, proving that they remain diploid and that chromosome duplication failed in all genotypes. The averages for the values obtained in IR, IM and VP, for all genotypes, were, respectively, 28.39, 95.62% and 76.05%. Meiotic abnormalities met the standards for corn. These results reveal that only in H1700349 the obtaining of H showed efficiency, that the duplication of genotypes was not efficient and that all genotypes had medium and high indices of meiotic regularity, IM, IR and VP. Therefore, the protocol for obtaining H and DH was not efficient and the stress caused by it did not significantly affect the meiotic regularity of the analyzed genotypes. |
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