Genetic manipulation of tall fescue

Genetic manipulation of tall fescue (Festuca arnndinacea Schreb.) has not been altered by the discovery of the Acremonium coenophialum (Morgan-Jones and Gams) / grass interaction. However, tall fescue breeding programs have been affected greatly. The basic methods for genetically manipulating the grass have remained static. Tall fescue is an obligate out-crossing species, and most improvements are, therefore, captured in the form of an improved population developed through some form of mass or recurrent selection. What has changed is the breeder\u27s ability to recognize genetic differences in the grass because of the confounding effect of A. coenophialum on plant phenotype. It is, therefore, critical that breeders recognize A. coenophialum status in their plants prior to selection. The other major change in tall fescue breeding since the discovery of the A. coenophialum/grass interaction is a tremendous increase in breeding activity

Genetic manipulation of tall fescue

Genetic manipulation of tall fescue (Festuca arnndinacea Schreb.) has not been altered by the discovery of the Acremonium coenophialum (Morgan-Jones and Gams) / grass interaction. However, tall fescue breeding programs have been affected greatly. The basic methods for genetically manipulating the grass have remained static. Tall fescue is an obligate out-crossing species, and most improvements are, therefore, captured in the form of an improved population developed through some form of mass or recurrent selection. What has changed is the breeder\u27s ability to recognize genetic differences in the grass because of the confounding effect of A. coenophialum on plant phenotype. It is, therefore, critical that breeders recognize A. coenophialum status in their plants prior to selection. The other major change in tall fescue breeding since the discovery of the A. coenophialum/grass interaction is a tremendous increase in breeding activity

ALTERATION OF PLANTS VIA GENETICS AND PLANT BREEDING

Plant breeding is man-directed evolution. Plant breeders manipulate the genetic resources of a species, i.e., its germplasm, to produce plants that are of increased value to humanity. The same analogy applies to animal improvement programs. All of our major food crops and all of our domestic animals and their respective breeds, strains, or cultivars were developed by this process. Although humans have successfully manipulated the genetic resources of plants and animals for several thousand years, the science of genetics and breeding was not developed until this century

Considerations in Breeding Endophyte-Free Tall Fescue Forage Cultivars

Breeding tall fescue (Festuca arundinacea Schreb.) cultivars that are free of the endophytic fungus Acremonium coenophialum Morgan-Jones and Gams [previously identified and referred to as Epichloe typhina (Fries) Tulasne] is necessary to improve animal performance. The techniques used in developing new cultivars are not greatly different from those used previously, with one exception. Prior to the evaluation of new tall fescue lines or populations, the endophyte needs to be eliminated from the seed or the plants. Several techniques utilizing aging, heat, or chemical treatment are being used to effectively accomplish this in the seed. Methods for permanently eliminating the endophyte from plants are not available. The major new considerations in breeding endophyte-free tall fescue cultivars do not involve drastic changes in breeding methodology, but rather focus on new objectives. In the past, much effort was directed at overcoming the toxic effects of the endophyte. Now, breeders can focus their efforts on objectives such as increasing digestibility, physiological efficiency, mineral uptake, and insect and disease resistance. Losses in stress tolerance due to the elimination of the endophyte from tall fescue may also have to be addressed, especially in areas of marginal adaptation

Considerations in Breeding Endophyte-Free Tall Fescue Forage Cultivars

Breeding tall fescue (Festuca arundinacea Schreb.) cultivars that are free of the endophytic fungus Acremonium coenophialum Morgan-Jones and Gams [previously identified and referred to as Epichloe typhina (Fries) Tulasne] is necessary to improve animal performance. The techniques used in developing new cultivars are not greatly different from those used previously, with one exception. Prior to the evaluation of new tall fescue lines or populations, the endophyte needs to be eliminated from the seed or the plants. Several techniques utilizing aging, heat, or chemical treatment are being used to effectively accomplish this in the seed. Methods for permanently eliminating the endophyte from plants are not available. The major new considerations in breeding endophyte-free tall fescue cultivars do not involve drastic changes in breeding methodology, but rather focus on new objectives. In the past, much effort was directed at overcoming the toxic effects of the endophyte. Now, breeders can focus their efforts on objectives such as increasing digestibility, physiological efficiency, mineral uptake, and insect and disease resistance. Losses in stress tolerance due to the elimination of the endophyte from tall fescue may also have to be addressed, especially in areas of marginal adaptation

The fescue fungus problem

"Tall fescue has been widely accepted as a forage plant. It is particularly well adapted to the southern portion of the cornbelt where it has been planted on millions of acres of pasture lands."--First page.H.N. Wheaton and D.A. Sleper (Department of Agronomy) and Einar Palm (Department of Pathology, College of Agriculture)New 10/84/20

A survey of restriction fragment length polymorphisms in tall fescue and its relatives

Restriction fragment length polymorphisms (RFLPs) have several advantages over conventional genetic markers and as a result have received increased attention from plant breeders and geneticists. The objective of this study was to construct a tall fescue (Festuca arundinacea Schreb.) genomic library and to survey RFLPs in tall fescue and its relatives. Using plasmid pUC19 as a vector and Escherichia coli XL1-Blue cells as hosts, the first reported PstI genomic DNA library has been established from hexaploid (2n = 6x = 42) tall fescue. The genomic clones were evaluated using nine genotypes from three species of Festuca and three restriction enzymes (BamHI, EcoRI, and HindIII). One hundred and seventy-four probes gave readable results, of which 21% were repetitive and 79% single-copy. The single-copy probes revealed good polymorphism in tall fescue. Approximately 21% of the probes did not cross hybridize to any of the diploids or tetraploids or both and, therefore, represented genome-specific clone

Genetic Mapping of Soybean Cyst Nematode (Heterodera glycines) Resistance to Enhance Soybean Production in the United States [abstract]

Only abstract of poster available.Track V: BiomassSoybean cyst nematode (SCN, Heterodera glycines) is the most destructive pest of soybean in the United States, resulting in an annual extensive yield loss of approximately $1.5 billion in the United States alone. Breeding for resistance to SCN is the most effective approach to control this pest. However, most of commercial soybean varieties resistant to SCN were mainly derived from a few common resistant sources. The continuation of growing the same resistant cultivar(s) have resulted in SCN population shifts and loss of SCN resistance; thus it highlights a need of further investigation to mine new resistant genes from new resistant sources for soybean improvement. As a leading group on SCN research in the United States, the University of Missouri SCN researchers have been continuing the evaluation of exotic soybean germplasm for broad-based resistance to multi-HG types of SCN, the identification and mapping of novel quantitative trait loci (QTL)/gene(s), and the discovery of genetic markers for marker-assisted selection (MAS) programs. Using many plant introductions (PIs) with high resistance to multi-SCN HG types, we have developed genetic populations for molecular characterization and QTL mapping. These efforts led to the discovery of many novel QTL underlying the resistance to multi-SCN HG types. With sequence information using the genome-wide Illumina/Solexa sequencing technology, we have developed hundreds of genetic markers associated with the target QTL. Along with the soybean physical and genetic maps, these markers will provide a powerful genomics tool facilitating our efforts toward fine-mapping and positional cloning of candidate genes for SCN resistance. Moreover, the QTL associated genetic markers are greatly useful to incorporate novel resistant genes into new soybean varieties through the MAS approach. With SCN resistant soybean varieties, soybean yield and productivity will be increased and, in turn, enhance the seed oil production; which will significantly be an important source for the development of biofuel

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

Mutational analysis of the major soybean UreF paralogue involved in urease activation

The soybean genome duplicated ∼14 and 45 million years ago and has many paralogous genes, including those in urease activation (emplacement of Ni and CO2 in the active site). Activation requires the UreD and UreF proteins, each encoded by two paralogues. UreG, a third essential activation protein, is encoded by the single-copy Eu3, and eu3 mutants lack activity of both urease isozymes. eu2 has the same urease-negative phenotype, consistent with Eu2 being a single-copy gene, possibly encoding a Ni carrier. Unexpectedly, two eu2 alleles co-segregated with missense mutations in the chromosome 2 UreF paralogue (Ch02UreF), suggesting lack of expression/function of Ch14UreF. However, Ch02UreF and Ch14UreF transcripts accumulate at the same level. Further, it had been shown that expression of the Ch14UreF ORF complemented a fungal ureF mutant. A third, nonsense (Q2*) allelic mutant, eu2-c, exhibited 5- to 10-fold more residual urease activity than missense eu2-a or eu2-b, though eu2-c should lack all Ch02UreF protein. It is hypothesized that low-level activation by Ch14UreF is ‘spoiled’ by the altered missense Ch02UreF proteins (‘epistatic dominant-negative’). In agreement with active ‘spoiling’ by eu2-b-encoded Ch02UreF (G31D), eu2-b/eu2-c heterozygotes had less than half the urease activity of eu2-c/eu2-c siblings. Ch02UreF (G31D) could spoil activation by Chr14UreF because of higher affinity for the activation complex, or because Ch02UreF (G31D) is more abundant than Ch14UreF. Here, the latter is favoured, consistent with a reported in-frame AUG in the 5' leader of Chr14UreF transcript. Translational inhibition could represent a form of ‘functional divergence’ of duplicated genes