Genetic control of traits related to phosphorus use efficiency in tropical maize.

Knowing the inheritance of traits is essential to establish selection strategies in breeding programs. The aim of this study was to determine the genetic control of traits related to the phosphorus use efficiency in maize. A total of 280 progenies were developed according to design III, which were evaluated in the field under high and low phosphorus (P) availability. The genetic variance components were estimated for the agronomic traits and indices that define P use efficiency. The results indicated that the additive and dominance effects were important in explaining the genetic variability for the flowering time, grain yield and P efficiency indices. However, dominance effects prevailed, indicating that breeding efforts should be made to develop hybrids exploiting the heterosis for traits related to P use efficiency

Mapeamento de locos de características quantitativas associados à composição de carcaça, no cromossomo seis de suíno

Uma população de suínos, composta de 550 animais F2, foi produzida a partir do intercruzamento da geração FI, obtida pelo cruzamento divergente de dois machos da raça nativa brasileira Piau com 18 fêmeas comerciais. O objetivo do trabalho foi mapear locos de características quantitativas (QTL) associados a cortes de carcaça. Os animais foram genotipados para I3 marcadores microssatélites, distribuídos no cromossomo 6 de suínos. As características avaliadas foram: peso total do pernil, peso do pernil sem pele e sem capa de gordura, peso total da copa, peso da copa sem pele e sem capa de gordura, peso total da paleta, peso da paleta sem pele e sem capa de gordura, peso total do carré, peso do lombo, peso total do bacon, peso das costelas, peso total da papada, peso do filezinho e peso da banha rama. Utilizou-se o método de regressão por intervalo de mapeamento por meio do programa QTL Express. Foram encontrados indicativos de QTL para peso de pernil limpo, peso de paleta, peso de lombo e peso de filezinho. A região genõmica deve ser saturada com marcadores adicionais para confirmar a presença de QTL reais

Caracterização molecular de milho e sorgo para aplicação nos programas de melhoramento da Embrapa.

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Parâmetros genéticos de uma população de milho em níveis contrastantes de nitrogênio.

O objetivo desse trabalho foi caracterizar uma população de milho por meio da análise de parâmetros genéticos em baixa e alta disponibilidade de nitrogênio. Assim, foi realizado experimento em delineamento em blocos ao acaso, com 162 linhagens, em dois ambientes contrastantes quanto à disponibilidade de nitrogênio, em esquema fatorial com três repetições. A população apresentou variabilidade genética para produtividade de grãos em baixo nitrogênio, com redução na média de altura de espiga, teor de clorofila, número de espigas, peso de espiga e produtividade de grãos em relação ao ambientes sem estresse. Os coeficientes de correlação genética entre produtividade de grãos e as outras características variaram de acordo com as doses de nitrogênio aplicadas. O número de espigas apresentou alta correlação genética com produtividade de grãos sob estresse, além de maior herdabilidade comparada à obtida em alto nitrogênio, possibilitando assim seu uso na seleção indireta de linhagens produtivas de milho cultivadas sob estresse de nitrogênio

Evaluation of high quality protein maize (QPM) hybrids obtained by conversion of normal inbred lines.

Two experimental QPM hybrids obtained by lhe partial conversion of three elite inbred lines by modified backcrossing were evaluated and compared to the normal versions of the same hybrids. Thirteen agronomic and 12 grain quality traits were evaluated. The hybrids were also anaJyzed by SSR markers in order to evaluate the genetic relationship among them. Results demonstrated that the converted QPM hybrids presented a better protein quality and a similar agronomic performance for most of the evaluated traits, including grain yield, in comparison to their normal versions. However, some of the deficiencies generally ascribed to QPM hybrids, such as a higher lodgíng percentage, thicker cobs, and shorter kernels were maintained up to this stage of the conversion process. In comparison to more recent elite hybrids, the normal versions as well as the converted QPM hybrids presented the worst performances in relation to the grain yield, thus indicating a loss of competitiveness

Genetic and molecular mechanisms of aluminum tolerance in plants.

Aluminum (Al) toxicity restricts root growth and agricultural yield in acid soils, which constitute approximately 40% of the potentially arable lands worldwide. The two main mechanisms of Al tolerance in plants are internal detoxification of Al and its exclusion from root cells. Genes encoding membrane transporters and accessory transcription factors, as well as cis-elements that enhance gene expression, are involved in Al tolerance in plants; thus studies of these genes and accessory factors should be the focus of molecular breeding efforts aimed at improving Al tolerance in crops. In this review, we describe the main genetic and molecular studies that led to the identification and cloning of genes associated with Al tolerance in plants. We include recent findings on the regulation of genes associated with Al tolerance. Understanding the genetic, molecular, and physiological aspects of Al tolerance in plants is important for generating cultivars adapted to acid soils, thereby contributing to food security worldwide

Self-dual solitons in N=2 supersymmetric semilocal Chern-Simons theory

We embed the semilocal Chern-Simons-Higgs theory into an N=2 supersymmetric system. We construct the corresponding conserved supercharges and derive the Bogomol'nyi equations of the model from supersymmetry considerations. We show that these equations hold provided certain conditions on the coupling constants as well as on the Higgs potential of the system, which are a consequence of the huge symmetry of the theory, are satisfied. They admit string-like solutions which break one half of the supersymmetries --BPS Chern-Simons semilocal cosmic strings-- whose magnetic flux is concentrated at the center of the vortex. We study such solutions and show that their stability is provided by supersymmetry through the existence of a lower bound for the energy, even though the manifold of the Higgs vacuum does not contain non-contractible loops.Comment: 12 pages, LaTeX, no figures, to appear in Modern Physics Letters