Leaf tensile strength, "in vitro" digestibility, and fiber component relationships in tall fescue

Em um programa de melhoramento de forrageiras, a identificação de plantas com elevado valor nutritivo, é um dos fatores importantes para melhorar o desempenho animal. Interrelações significativas entre características físicas e químicas talvez possam ser utilizadas como um critério para a seleção de novas cultivares de festuca-alta de maior valor nutritivo. Os objetivos deste experimento foram: a. avaliar a tensão foliar (TF) e a digestibilidade in vitro da matéria seca (DIVMS) e dos constituintes da parede celular; b. analisar as associações entre essas características com a TF e c. determinar a eficiência da TF como uma técnica para a seleção de novos germoplasmas de festuca-alta, com forragem de melhor qualidade. Setenta e um genótipos de festuca alta foram avaliados neste experimento. Foi encontrada uma variabilidade genética significativa para TF nesta população de festuca-alta. Geralmente, as correlações de TF com DIVMS e componentes da parede celular não foram significativas, enquanto que as correlações de DIVMS com os componentes da parede celular foram altamente significativas e negativas. Conforme esperado, houve baixa repetibilidade de correlações de caracteres nos dois anos. A "análise de coeficientes de trilha" demonstrou que a celulose e a lignina foram os caracteres com os maiores efeitos diretos na TF e na DIVMS.In a forage breeding program it is necessary to identify germplasms with high forage quality, able to positively influence animal performance. The interrelationships between leaf tensile strength (LTS) and chemical composition parameters may provide a useful criterion for screening tall fescue (Festuca arundinacea Schreb.) for herbage quality in a breeding program. Seventy-one genetically diverse genotypes of tall fescue were randomly selected from a broad-based population to evaluate LTS (leaf tensile strength), in vitro dry matter digestibility (IVDMD), acid detergent fiber (ADF), neutral detergent fiber (NDF), cellulose (CELL), lignin (ADL), hemicellulose (HEMI), ADL/ADF and ASH, to determine the associations among these traits with LTS, and the importance of LTS as a technique for screening tall fescue for herbage quality. Significant genetic variation was found in this gene pool for LTS. The majority of the correlations of LTS with IVDMD and with fiber components were not significantly different from zero while correlations of IVDMD with fiber components were highly significant and negative. As expected, character correlation repeatabilities between years were usually low. Path coefficient analysis showed that CELL and ADL were two important components with large direct effects on LTS and on IVDMD

Leaf tensile strength, "in vitro" digestibility, and fiber component relationships in tall fescue

Em um programa de melhoramento de forrageiras, a identificação de plantas com elevado valor nutritivo, é um dos fatores importantes para melhorar o desempenho animal. Interrelações significativas entre características físicas e químicas talvez possam ser utilizadas como um critério para a seleção de novas cultivares de festuca-alta de maior valor nutritivo. Os objetivos deste experimento foram: a. avaliar a tensão foliar (TF) e a digestibilidade in vitro da matéria seca (DIVMS) e dos constituintes da parede celular; b. analisar as associações entre essas características com a TF e c. determinar a eficiência da TF como uma técnica para a seleção de novos germoplasmas de festuca-alta, com forragem de melhor qualidade. Setenta e um genótipos de festuca alta foram avaliados neste experimento. Foi encontrada uma variabilidade genética significativa para TF nesta população de festuca-alta. Geralmente, as correlações de TF com DIVMS e componentes da parede celular não foram significativas, enquanto que as correlações de DIVMS com os componentes da parede celular foram altamente significativas e negativas. Conforme esperado, houve baixa repetibilidade de correlações de caracteres nos dois anos. A "análise de coeficientes de trilha" demonstrou que a celulose e a lignina foram os caracteres com os maiores efeitos diretos na TF e na DIVMS.In a forage breeding program it is necessary to identify germplasms with high forage quality, able to positively influence animal performance. The interrelationships between leaf tensile strength (LTS) and chemical composition parameters may provide a useful criterion for screening tall fescue (Festuca arundinacea Schreb.) for herbage quality in a breeding program. Seventy-one genetically diverse genotypes of tall fescue were randomly selected from a broad-based population to evaluate LTS (leaf tensile strength), in vitro dry matter digestibility (IVDMD), acid detergent fiber (ADF), neutral detergent fiber (NDF), cellulose (CELL), lignin (ADL), hemicellulose (HEMI), ADL/ADF and ASH, to determine the associations among these traits with LTS, and the importance of LTS as a technique for screening tall fescue for herbage quality. Significant genetic variation was found in this gene pool for LTS. The majority of the correlations of LTS with IVDMD and with fiber components were not significantly different from zero while correlations of IVDMD with fiber components were highly significant and negative. As expected, character correlation repeatabilities between years were usually low. Path coefficient analysis showed that CELL and ADL were two important components with large direct effects on LTS and on IVDMD

Intricate environment-modulated genetic networks control isoflavone accumulation in soybean seeds

<p>Abstract</p> <p>Background</p> <p>Soybean (<it>Glycine max </it>[L] Merr.) seed isoflavones have long been considered a desirable trait to target in selection programs for their contribution to human health and plant defense systems. However, attempts to modify seed isoflavone contents have not always produced the expected results because their genetic basis is polygenic and complex. Undoubtedly, the extreme variability that seed isoflavones display over environments has obscured our understanding of the genetics involved.</p> <p>Results</p> <p>In this study, a mapping population of RILs with three replicates was analyzed in four different environments (two locations over two years). We found a total of thirty-five main-effect genomic regions and many epistatic interactions controlling genistein, daidzein, glycitein and total isoflavone accumulation in seeds. The use of distinct environments permitted detection of a great number of environment-modulated and minor-effect QTL. Our findings suggest that isoflavone seed concentration is controlled by a complex network of multiple minor-effect loci interconnected by a dense epistatic map of interactions. The magnitude and significance of the effects of many of the nodes and connections in the network varied depending on the environmental conditions. In an attempt to unravel the genetic architecture underlying the traits studied, we searched on a genome-wide scale for genomic regions homologous to the most important identified isoflavone biosynthetic genes. We identified putative candidate genes for several of the main-effect and epistatic QTL and for QTL reported by other groups.</p> <p>Conclusions</p> <p>To better understand the underlying genetics of isoflavone accumulation, we performed a large scale analysis to identify genomic regions associated with isoflavone concentrations. We not only identified a number of such regions, but also found that they can interact with one another and with the environment to form a complex adaptable network controlling seed isoflavone levels. We also found putative candidate genes in several regions and overall we advanced the knowledge of the genetics underlying isoflavone synthesis.</p

Genomic strategies for soybean oil improvement and biodiesel production

Track II: Transportation and BiofuelsIncludes audio file (21 min.)Soybean oil, a promising renewable energy resource, comprises 73% of biodiesel in addition to other industrial applications. Missouri is the fifth largest state in the US for soybean plantation. With the target to produce 225 million gallons of biodiesel by 2015 from the current 75 million gallons produced in 2005, efforts should not only focus on expanding the number of oil crops to meet the demand but also to increase the amount of oil per hectare for each crop. Considering the ever increasing need for biodiesel and the potential for Missouri to play a major role in national and international demand, We, at the National Center for Soybean Biotechnology focus on discovering the genetic factors that are responsible for oil content in soybean using genetic and genomic strategies. The long term goal is to apply discoveries in breeding programs and biotechnology for the development of improved soybean cultivars with increased oil content that will make this crop more competitive in end-uses. Our multidisciplinary approaches include traditional Quantitative Trait Loci (QTL) mapping, association mapping, bioinformatics and transgenics by developing new resources and utilizing already available resources such as mapping populations, diverse germplasm collections, genome sequence information and transgenes. In addition to total oil content, we are focusing on improving quality traits such as oleic acid which has direct human health benefits and application in biodiesel production. With the use of advanced genomic technologies, genetic materials, and synergistic efforts involving intra- and inter institutional collaborations, we believe that our current and future research will contribute substantially to biodiesel production. Increased production using high oil soybean cultivars will not only increase the economic gains to farmers/growers but also facilitate the US to emerge as the global leader in biodiesel production

Selection of a core set of RILs from Forrest × Williams 82 to develop a framework map in soybean

Soybean BAC-based physical maps provide a useful platform for gene and QTL map-based cloning, EST mapping, marker development, genome sequencing, and comparative genomic research. Soybean physical maps for “Forrest” and “Williams 82” representing the southern and northern US soybean germplasm base, respectively, have been constructed with different fingerprinting methods. These physical maps are complementary for coverage of gaps on the 20 soybean linkage groups. More than 5,000 genetic markers have been anchored onto the Williams 82 physical map, but only a limited number of markers have been anchored to the Forrest physical map. A mapping population of Forrest × Williams 82 made up of 1,025 F8 recombinant inbred lines (RILs) was used to construct a reference genetic map. A framework map with almost 1,000 genetic markers was constructed using a core set of these RILs. The core set of the population was evaluated with the theoretical population using equality, symmetry and representativeness tests. A high-resolution genetic map will allow integration and utilization of the physical maps to target QTL regions of interest, and to place a larger number of markers into a map in a more efficient way using a core set of RILs

Identification of Homogentisate Dioxygenase as a Target for Vitamin E Biofortification in Oilseeds

Soybean (Glycine max) is a major plant source of protein and oil and produces important secondary metabolites beneficial for human health. As a tool for gene function discovery and improvement of this important crop, a mutant population was generated using fast neutron irradiation. Visual screening of mutagenized seeds identified a mutant line, designated MO12, which produced brown seeds as opposed to the yellow seeds produced by the unmodified Williams 82 parental cultivar. Using forward genetic methods combined with comparative genome hybridization analysis, we were able to establish that deletion of the GmHGO1 gene is the genetic basis of the brown seeded phenotype exhibited by the MO12 mutant line. GmHGO1 encodes a homogentisate dioxygenase (HGO), which catalyzes the committed enzymatic step in homogentisate catabolism. This report describes to our knowledge the first functional characterization of a plant HGO gene, defects of which are linked to the human genetic disease alkaptonuria. We show that reduced homogentisate catabolism in a soybean HGO mutant is an effective strategy for enhancing the production of lipid-soluble antioxidants such as vitamin E, as well as tolerance to herbicides that target pathways associated with homogentisate metabolism. Furthermore, this work demonstrates the utility of fast neutron mutagenesis in identifying novel genes that contribute to soybean agronomic traits