Synthetic wheat is developed by crossing tetraploid species ( Triticum turgidum , AABB) with a diploid species ( Aegilops tauschii , DD), followed by chromosome duplication through the use of colchicine to restore the resultant sterile hybrid to a fertile hexaploid plant. The main importance of producing synthetically improved wheat is to increase their genetic variability and to incorporate genes that code for resistance to biotic and abiotic stressors. This study aimed to evaluate the presence of micronuclei (MN) and the meiotic index (MI) in the tetrad phase in synthetic wheat accessions and cultivars ( Triticum aestivum ) stored at the Germplasm Bank of Embrapa Trigo (Brazil), in order to identify and select genetically stable accessions for plant improvement. Five plants were collected by genotype, prior to anthesis, and the tissues were fixed in Carnoy solution. Cytological slides were prepared by the smash method, and the cells were dyed with 1% acetocarmine and observed under an optical microscope. Presence of MN was observed in all genotypes analyzed, and variability of genetic stability was reported in the two years of analysis. In 2014, the highest MI of synthetic wheat accessions was 96.86% and the lowest was 46.32%. In 2015, the highest MI was 96.60% and the lowest was 47.96%. Based on the results, some genotypes were considered meiotically stable and suitable for use in wheat breeding programs.
O conteúdo dos artigos e seus dados em sua forma, correção e confiabilidade são de responsabilidade exclusiva dos autores. Permitido o download da obra e o compartilhamento desde que sejam atribuídos créditos aos autores, mas sem a possibilidade de alterá-la de nenhuma forma ou utilizá-la para fins comerciais. Conselho Editorial Ciências Humanas e Sociais Aplicadas APRESENTAÇÃO O termo "genética" nos últimos anos ganhou uma conotação cada vez mais importante e acessível à população. Podemos dizer que a genética saiu da rotina laboratorial e da sala de aula para adentrar as casas da população, seja por informação ou na forma de produto. Isso porque a revolução tecnológica contribuiu grandemente com o avanço no campo da pesquisa básica e aplicada à genética, e as descobertas propciadas por tecnologias mais apuradas possibilitaram um entendimento mais amplo desta importante área. A genética como sabemos possui um campo vasto de aplicabilidades que podem colaborar e cooperar grandemente com os avanços científicos e tecnológicos. O acelerado mundo das descobertas científicas caminha a passos largos e rápidos no sentido de transformar a pesquisa básica em aplicada, portanto é relevante destacar que investimentos e esforços nessa área contribuem grandemente com o desenvolvimento de uma nação. O livro "Inventários e Recursos Genéticos" aqui apresentado, aborda assuntos relativos aos avanços e dados científicos publicados de cunho voltado para a utilização dos recursos genéticos disponíveis na área ambiental, microbiológica dentre outras diversas que cientistas tem gastado esforços para compreender. Assim, são diversas as possibilidades de aplicações genéticas em diversos campos, neste livro tentaremos otimizar os conceitos dos recursos genéticos abordando plantas medicinais, segurança alimentar, sanidade animal, microrganismos patogênicos, identificação molecular, caracterização morfoagronômica, Banco de DNA, metabólitos secundários, melhoramento genético, análise multivariada, bioinformática, expressão de genes, viabilidade polínica, Germoplasma, recursos genéticos, cultivares, Qualidade de sementes; seleção de plantas; melhoramento genético da mamoneira, simulações em Easypop, fluxo gênico, fragmentação florestal, análise de diversidade genética de Nei, Coeficientes de endogamia, demonstrando ferramentas genéticas e moleculares usadas em diferentes estudos que estão diretamente relacionados ao dia-a-dia da população. Desejamos que este material possa somar de maneira significativa aos novos conceitos aplicados à genética Parabenizamos cada autor pela teoria bem fundamentada aliada à resultados promissores, e principalmente à Atena Editora por permitir que o conhecimento seja difundido e disponibilizado para que as novas gerações se interessem cada vez mais pelo ensino e pesquisa em genética.
Wheat seeds infected with Pyrenophora tritici-repentis, the causal agent of tan spot, are partially responsible for outbreaks caused by this pathogen. Seed lots with a high incidence of P. tritici-repentis must be rapidly acquired for transmission and pathogen-control studies. Therefore, the aim of this study was to determine whether changes in water potential of culture medium and variations in inoculation time might favor the infection of wheat seeds by P. tritici-repentis without compromising seed viability. Colonies of P. tritici-repentis were grown on potato-dextrose-agar (PDA) culture medium, adjusted to a water potential of -0.36 MPa, under water stress induced by mannitol at potentials of -0.4, -0.6, -0.8, -1.0, and -1.2 MPa. Analyses were carried out to determine mycelial growth index and seed exposure time to the culture medium to start germination as a function of water potential. Afterwards, wheat seeds were placed in contact with colonies of P. tritici-repentis for 24, 48, and 72 hours at potentials of -0.4, -0.6, -0.8, -1.0, and -1.2 MPa. The experiment was arranged in a completely randomized design, in a factorial scheme (water potential × inoculation time). Rates of germination, seedling emergence in soil, and seed infection were assessed. Mycelial growth was stimulated at lower water potentials, which germinated faster. A 24-hour inoculation time and a -0.4 MPa water potential were efficient to infect wheat seeds with P. tritici-repentis, without hindering seedling germination and emergence under laboratory conditions.
The objective of this study was to evaluate genetic stability by determining the meiotic index (MI) and pollen viability in F1RC2 segregating populations, obtained by the crosses between wheat commercial cultivars and synthetic wheat, aimed at introgression/genetic resistance. For MI, three ears were collected per genotype, before anthesis, and they were fixed in Carnoy’s solution. The cytological slides were prepared by crushing the anthers and staining with 1% acetocarmine, and the normal tetrads and the ones with micronuclei were observed under a light microscope. For pollen viability, the ears were collected at the stage of mature pollen grain. The methodological procedure was similar to that of the tetrads, evaluating the pollen grains as viable, with little starch, with two pores, different sizes and non-viable. The pollen grain size was measured by the Axion Vision software. All the segregating populations with MI above 90% and high pollen viability (above 85%) reflected a stable meiotic behavior. About the variation in size, the CIGM90.909/BRS 179 cross showed pollen grains with 58.43 μm and CIGM93.298/BRS Guamirim, 47.15 μm. According to the results, wheat segregating populations were considered meiotically stable and suitable for use in wheat breeding programs and for incorporation of new important genes.
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