Regeneração de plantas a partir do cultivo de óvulos de Citrus reticulata cv. Dancy

Undeveloped ovules of Citrus reticulata Blanco cv. Dancy were cultivated with the objective to determinate the effect of pollination, harvesting time and culture conditions appropiated for induction of embryogenesis and embryo production. It was verified the effect of in vivo grafting of cotiledonary embryos, in ten-month-old rootstock obtained from seeds, on the rapidity of obtention of disease-free plants and on the reduction of the juvenility stage. Ovule originated from pollinated and non-pollinated flowers collected 7, 14, 21 and 28 days after anthesis grown under light and dark conditions were cultured in basic medium MT, added with 500 mg.L-1 of malt extract. Cotiledonary embryos, 4-6 mm long, obtained in vitro were grafted in vivo on rootstocks. Embryos were directly obtained from ovule culture, however it was observed the formation of a high number of abnormal embryos in all treatments. Whole plants were developed on the same basic medium. It was not observed the formation of callus until 120 days. Differences related to the percentage of ovules that induced embryos and the number of embryos were observed in all treatments. The success rate of embryo grafting was 23%, however, it was observed a fast seedling development, which is a promissing technique for breeding programs and maybe in the mass propagation of virus-free plants, in case the juvenile phase be reduced.Este trabalho foi desenvolvido com o objetivo de verificar o efeito da polinização, época de coleta, condição de cultivo de óvulos não desenvolvidos de Citrus reticulata Blanco cv. Dancy, quanto à indução de embriogênese e o número de embriões desenvolvidos e verificar o efeito da enxertia in vivo de embriões cotiledonares, em porta-enxertos obtidos a partir de sementes, sobre a rapidez de obtenção de plantas sadias e redução do período de juvenilidade. Óvulos originados de flores com e sem polinização, coletados aos 7, 14, 21 e 28 dias, mantidos sob luz e no escuro foram cultivados em meio básico MT, suplementado com 500 mg.L-1 de extrato de malte. Embriões cotiledonares, obtidos diretamente do cultivo de óvulos, com 4-6 mm de comprimento foram enxertados diretamente em porta-enxertos com 10 meses de idade. Não houve formação de nenhum calo até os 120 dias após o início do cultivo. Entre os tratamentos observaram-se diferenças quanto à porcentagem de óvulos que induziram embriões e ao número de embriões formados. Plantas inteiras foram desenvolvidas no mesmo meio básico. A porcentagem de pegamento dos enxertos foi de 23%, entretanto, foi observado um rápido desenvolvimento das mudas, mostrando boas perspectivas desta técnica em programas de melhoramento e talvez na propagação de plantas livres de viroses, caso a fase juvenil seja reduzida

Componentes de produção e caracteres reprodutivos, fisiológicos e de raiz usados na seleção precoce para eficiência do uso de nitrogênio em milho

The objective of this work was to examine the possibility of using yield components and reproductive, physiological, and root traits in early selection for nitrogen use efficiency (NUE) in corn. Sixty-four inbred lines were evaluated under two nitrogen fertilization levels: ideal and low. The evaluations were performed at three phenological stages: eight fully-expanded leaves, tasseling stage, and physiological maturity. It is possible to select superior lines for NUE, but the yield components did not show differential behavior under the different nitrogen levels evaluated. Root, reproductive, and physiological traits are not promising for early selection of corn lines with high NUE. Likewise, the eight-leaves and tasseling stages were not promising for this purpose, since NUE should be estimated taking grain yield into account. However, indirect selection for NUE can be performed via number of ears or using the selection index considering number and weight of ears.O objetivo deste trabalho foi examinar a possibilidade de usar componentes de produção e caracteres reprodutivos, fisiológicos e de raiz na seleção precoce para eficiência de uso de nitrogênio (EUN) em milho. Foram avaliadas 64 linhagens em dois regimes de adubação nitrogenada: ideal e baixo. As avaliações foram feitas em três estádios fenológicos: oito folhas completamente expandidas, florescimento masculino e maturação fisiológica. É possível selecionar linhagens superiores quanto à EUN, mas os componentes de produção não tiveram comportamento diferencial sob os diferentes níveis de nitrogênio avaliados. Os caracteres radiculares, reprodutivos e fisiológicos não se mostraram confiáveis para seleção precoce de linhagens de milho com elevada EUN. De forma semelhante, os estádios de oito folhas e de florescimento masculino não se mostraram promissores para esse propósito, uma vez que, para a estimação da EUN, deve-se levar em consideração a produção de grãos. Entretanto, a seleção indireta para EUN pode ser feita via número de espigas ou com o uso de índice de seleção que considere número e peso de espigas

Variabilidade de genótipos de milho quanto à composição de carotenoides nos grãos

The objective of this work was to characterize 134 maize (Zea mays) genotypes, for carotenoids content and build a genetic profile to facilitate future breeding to increase grain nutritional value (biofortification). Seeds came from experimental fields and from the Banco Ativo de Germoplasma of Embrapa Milho e Sorgo, Sete Lagoas, MG, Brazil. The genotypes were commercial hybrids, varieties, and inbred lines developed by the Embrapa biofortification program and other accessions, chosen for their yellow-orange endosperm color. Total grain carotenoids, carotenes, xanthophylls (monohydroxylates and dihydroxylates) were determined by chromatographic-spectrophotometric methods. The detected averages were: 22.34 µg g-1 for total carotenoids, 2.55 µg g-1 for carotenes, 3.86 μgág-1 for monohydroxylated xanthophylls, and 15.93 µg g-1 for dihydroxylated xanthophylls. The genotypes variability was divided into 18 groups by the method of Tocher. The Embrapa germplasm has variability and potential for development of maize lines biofortified for total of provitamin A carotenoids.O objetivo deste trabalho foi caracterizar e avaliar a variabilidade quanto ao teor e perfil de carotenoides nos grãos de 134 genótipos de milho (Zea mays), com vistas à utilização em programas de biofortificação. Os materiais foram provenientes dos campos experimentais e do Banco Ativo de Germoplasma da Embrapa Milho e Sorgo, Sete Lagoas, MG. São cultivares e híbridos comerciais, linhagens-elite e outros acessos escolhidos com base na coloração amarelo-alaranjada do endosperma. A quantificação do teor de carotenoides totais, carotenos e xantofilas mono-hidroxilada e di-hidroxilada dos grãos foi realizada por método cromatográfico-espectrofotométrico. As médias encontradas nos grãos foram 22,34 µg g-1 de carotenoides totais, 2,55 µg g-1 de carotenos, 3,86 µg g-1 de xantofilas mono-hidroxiladas e 15,93 µg g-1 de xantofilas di-hidroxiladas. Os genótipos foram agrupados em 18 grupos pelo método de Tocher. O germoplasma da Embrapa possui potencial para ser usado em programas de desenvolvimento de linhagens de milho biofortificadas, quanto ao total de carotenoides pró-vitamina A

Características de tolerância à seca em genótipos de uma coleção nuclear de arroz de terras altas

Resumo:O objetivo deste trabalho foi avaliar características morfofisiológicas relacionadas à tolerância ao estresse hídrico em genótipos de uma coleção nuclear temática de arroz de terras altas, bem como identificar os materiais mais tolerantes. Foram avaliados 100 genótipos de arroz de terras altas em experimentos conduzidos com e sem estresse por deficiência hídrica. Os genótipos tenderam a aumentar o número de dias para o florescimento (FLO) e a diminuir a altura (ALT), na condição de estresse, mas manifestaram ampla variação de comportamento. A esterilidade das espiguetas (EST) foi a característica mais importante para a seleção, nas duas condições de cultivo, em razão de sua elevada correlação negativa com a produtividade. O número de perfilhos não diferiu entre os genótipos na condição sem estresse, mas houve diferença significativa sob estresse hídrico. Os genótipos Ligeiro e Canela de Ferro apresentaram baixos índices de susceptibilidade à seca (ISS), mas baixa produtividade em ambas as condições de cultivo; já os materiais Catetão, Jatobá e Arroz do Maranhão apresentaram elevada produtividade sob estresse e valores de ISS relativamente baixos. EST, FLO, ALT e ISS são características morfofisiológicas relacionadas à tolerância à seca, e os genótipos Catetão, Jatobá e Arroz do Maranhão podem constituir boas fontes de genes para tolerância à seca em programas de melhoramento

The Relationship between Population Structure and Aluminum Tolerance in Cultivated Sorghum

Background: Acid soils comprise up to 50% of the world's arable lands and in these areas aluminum (Al) toxicity impairs root growth, strongly limiting crop yield. Food security is thereby compromised in many developing countries located in tropical and subtropical regions worldwide. In sorghum, SbMATE, an Al-activated citrate transporter, underlies the Alt(SB) locus on chromosome 3 and confers Al tolerance via Al-activated root citrate release. Methodology: Population structure was studied in 254 sorghum accessions representative of the diversity present in cultivated sorghums. Al tolerance was assessed as the degree of root growth inhibition in nutrient solution containing Al. A genetic analysis based on markers flanking Alt(SB) and SbMATE expression was undertaken to assess a possible role for Alt(SB) in Al tolerant accessions. In addition, the mode of gene action was estimated concerning the Al tolerance trait. Comparisons between models that include population structure were applied to assess the importance of each subpopulation to Al tolerance. Conclusion/Significance: Six subpopulations were revealed featuring specific racial and geographic origins. Al tolerance was found to be rather rare and present primarily in guinea and to lesser extent in caudatum subpopulations. Alt(SB) was found to play a role in Al tolerance in most of the Al tolerant accessions. A striking variation was observed in the mode of gene action for the Al tolerance trait, which ranged from almost complete recessivity to near complete dominance, with a higher frequency of partially recessive sources of Al tolerance. A possible interpretation of our results concerning the origin and evolution of Al tolerance in cultivated sorghum is discussed. This study demonstrates the importance of deeply exploring the crop diversity reservoir both for a comprehensive view of the dynamics underlying the distribution and function of Al tolerance genes and to design efficient molecular breeding strategies aimed at enhancing Al tolerance.CGIAR[G3007.04]McKnight FoundationFundacao de Amparo a Pesquisa do Estado de Minas Gerais (FAPEMIG)National Council for Scientific and Technological Development (CNPq

Correlações entre alguns caracteres agronômicos em soja (Glycine Max (l.) Merrill)

Estimaram-se as correlações fenotipicas, genotipicas e de ambiente entre alguns caracteres agronomicos em cinco populações F2 de soja, de quatro diferentes cruzamentos: 'Cometa' x 'IAC-8' em plantio convencional, 'Cometa' x 'IAC-8' em plantio por mudas, 'Cometa' x 'IAC-12', 'Parana' x 'IAC-8' 'Parana x 'IAC-12'. Elevadas estimativas de correlação genotipica foram encontradas em todos os cruzamentos, exceto no cruzamento 'Parana' x 'IAC-12', em que a maioria des estimativas de variancia genotipica foi negativa. Pelas estimativas obtidas, conclui-se que: 1) a seleção de plantas altas e precoces dificultada pela correlação genotipica positiva entre os caracteres dias para o florescimento e maturação com altura de planta; 2) a seleção da altura da planta pode ser realizada tanto por ocasião do florescimento como da maturação; 3) a seleção dos caracteres dias para o florescimento e dias para a maturação pode ser realizada com base apenas naquele caráter que apresentar major herdabilidade; o plantio por mudas, de modo geral, afetou as estimativas de correlação fenotipica e genotipica, gerando valores mais altos.Phenotypic, genotypic and enviroment correlations between some agronomia traits in five F2 populations of soybeans were estimated, in four different crosses: 'cometa' x 'IAC-8', 'cometa' x 'IAC-12', 'Parana' x 'IAC-8', 'Parana' x 'IAC-12'. Cross 'Cometa' x 'IAC-8' was tested under two conditions: direct and iachrect sowing. High estimates of genotypic correlation were found in all crosses, except 'Parana' x 'IAC-12', in which most of the estimates of genotypic variances were negative. It can be concluded that: 1) the selection of tall and early maturity plants is difficult due o the negative correlation between these traits; 2) the selection for plant height can done both at flowering or maturity time; 3) the selection for days to flowering and days to maturitycan be done together, based only on that character which has the higher heritability; 4) indirect sowing, in general, affected the genotypic and phenotypic correlations estimated, producing higher values

Marker-Assisted Recurrent Selection for Pyramiding Leaf Rust and Coffee Berry Disease Resistance Alleles in <i>Coffea arabica</i> L.

In this study, marker-assisted recurrent selection was evaluated for pyramiding resistance gene alleles against coffee leaf rust (CLR) and coffee berry diseases (CBD) in Coffea arabica. A total of 144 genotypes corresponding to 12 hybrid populations from crosses between eight parent plants with desired morphological and agronomic traits were evaluated. Molecular data were used for cross-certification, diversity study and resistance allele marker-assisted selection (MAS) against the causal agent of coffee leaf rust (Hemileia vastatrix) and coffee berry disease (Colletotrichum kahawae). In addition, nine morphological and agronomic traits were evaluated to determine the components of variance, select superior hybrids, and estimate genetic gain. From the genotypes evaluated, 134 were confirmed as hybrids. The genetic diversity between and within populations was 75.5% and 24.5%, respectively, and the cluster analysis revealed three primary groups. Pyramiding of CLR and CBD resistance genes was conducted in 11 genotypes using MAS. A selection intensity of 30% resulted in a gain of over 50% compared to the original population. Selected hybrids with increased gain also showed greater genetic divergence in addition to the pyramided resistance alleles. The strategies used were, therefore, efficient to select superior coffee hybrids for recurrent selection programs and could be used as a source of resistance in various crosses

A Phakopsora pachyrhizi Effector Suppresses PAMP-Triggered Immunity and Interacts with a Soybean Glucan Endo-1,3-β-Glucosidase to Promote Virulence

Asian soybean rust, caused by the fungus Phakopsora pachyrhizi, is one of the most important diseases affecting soybean production in tropical areas. During infection, P. pachyrhizi secretes proteins from haustoria that are transferred into plant cells to promote virulence. To date, only one candidate P. pachyrhizi effector protein has been characterized in detail to understand the mechanism by which it suppresses plant defenses to enhance infection. Here, we aimed to extend understanding of the pathogenic mechanisms of P. pachyrhizi based on the discovery of host proteins that interact with the effector candidate Phapa-7431740. We demonstrated that Phapa-7431740 suppresses pathogen-associated molecular pattern-triggered immunity (PTI) and that it interacts with a soybean glucan endo-1,3-β-glucosidase (GmβGLU), a pathogenesis-related (PR) protein belonging to the PR-2 family. Structural and phylogenetic characterization of the PR-2 protein family predicted in the soybean genome and comparison to PR-2 family members in Arabidopsis thaliana and cotton, demonstrated that GmβGLU is a type IV β-1,3-glucanase. Transcriptional profiling during an infection time course showed that the GmβGLU mRNA is highly induced during the initial hours after infection, coinciding with peak of expression of Phapa-7431740. The effector was able to interfere with the activity of GmβGLU in vitro, with a dose-dependent inhibition. Our results suggest that Phapa-7431740 may suppress PTI by interfering with glucan endo-1,3-β-glucosidase activity.This article is published as Bueno, Thays Vieira, Patricia Pereira Fontes, Valeria Yukari Abe, Alice Utiyama Saito, Renato Lima Senra, Liliane Santana Oliveira, Adriana Brombini Dos Santos et al. "A Phakopsora pachyrhizi effector suppresses PAMP-triggered immunity and interacts with a soybean glucan endo-1, 3-β-glucosidase to promote virulence." Molecular Plant-Microbe Interactions (MPMI) 35, no. 9 (2022): 779–790. DOI: 10.1094/MPMI-12-21-0301-R. The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2022