Glenn Fuller

Nutrient and growth interactions in soybeans colonized with Glomus fasciculatum and Rhizobium japonicum

SummaryGlycine max (L. Merr. cv. Amsoy 71) plants were grown in a greenhouse in a sand/perlite medium low in plant-available N and P. Plants were either inoculated with a vesicular-arbuscular mycorrhizal (VAM) fungus alone, a strain ofRhizobium japonicum alone, both endophytes together or were left non-inoculated to serve as a control. All combinations received a N-and P-free nutrient solution. Nodulated plants contained 4 to 5 times the phytomass of non-inoculated controls, and plants colonized with both the VAM fungus and Rhizobium were 18% greater in dry weight than nodulated, non-VAM plants due to a positive VAM times Rhizobium interaction. Nitrogen fixation, calculated from C2H4 and H2 data, was significantly higher in the tripartite symbiosis, with 80% of the increase attributable to increased nodule mass and 20% due to increases in specific nodule activity. Colonization by the VAM fungus and the development of vesicles increased significantly following nodulation. The synergistic interactions between the microsymbionts suggests that the response of the host to dual colonization is complex and depends on a balance between the three members of the symbiosis.

Mycotrophic growth and mutualistic development of host plant and fungal endophyte in an endomycorrhizal symbiosis

SummarySoybean plants colonized by the vesicular-arbuscular mycorrhizal (VAM) fungusGlomus fasciculatum were grown in pot cultures utilizing a composite greenhouse rooting medium. Development of fungal mycelia inside and outside the host root and total fungal biomass were determined from assays of fungal chitin. Growth and phosphorus uptake by VAM plants and uncolonized controls were compared. Mycotrophic growth in VAM plants occurred during the final six weeks of the 19-week growth period, when the concentration of available soil P fell below 10 μg P/g soil. Growth enhancement was most pronounced in the reproductive organs. The data suggest a relationship between the initiation of the reproductive phase in the host and the cessation of growth in the endophyte. Source-sink relationships and P availability appear to be factors influencing interactions between the symbionts.

High-oleic safflower oil. Stability and chemical modification

High-oleic acid safflower oil has been shown to have high-temperature oxidative stability comparable with that of hydrogenated vegetable oils. This stability, added to the ease of handling at low temperatures, should make the oil attractive as a commercial cooking oil. Epoxidation of the new safflower oil led to a product similar to epoxidized olive oil but lighter in color.

Development of two endomycorrhizal symbioses on soybean and comparison with phosphorus fertilization

SummarySoybean (Glycine max L. Merr. cv. Amsoy 71) plants were grown in a greenhouse in a soil very low in plant-available P, and plants were harvested 5 times over a 21-week growth period. Soybeans were inoculated with one of two species of VAM fungi or received daily one of three nutrient solutions of different P concentrations (0.0, 0.2, or 1.0mMP). Until week 9, the dry weights, leaf areas and developmental stage of soybeans inoculated withG. fasciculatum orG. mosseae were similar to the 1.0 or 0.2mMP-treated plants, respectively. Phosphorus concentrations were significantly lower in VAM plants at weeks 6 and 9 as compared to non-VAM soybeans given 1.0mMP, suggesting P input in VAM plants was immediately used for new growth. Total P input for VAM plants was linear over 21 weeks, and the average rate of P uptake for these plants was 0.19mg P d−1. Estimated specific P uptake rates (SPUR) for the mycorrhizae (VAM roots) were twice that of the control (0.0mMP) roots. The calculated SPURs forG. fasciculatum andG. mosseae hyphae were 95 and 120μg P g−1 VAM d−1 respectively, a 4 to 5 fold increase over non-inoculated roots, indicating more attention must be paid to P assimilation by VAM fungi in P-fixing substrates.

Fatty acid biosynthesis in novel ufa mutants of Neurospora crassa

New mutants of Neurospora crassa having the ufa phenotype have been isolated. Two of these mutants, like previously identified ufa mutants, require an unsaturated fatty acid for growth and are almost completely blocked in the de novo synthesis of unsaturated fatty acids. The new mutations map to a different chromosomal location than previously characterized ufa mutations. This implies that at least one additional genetic locus controls the synthesis of unsaturated fatty acids in Neurospora.

Agricultural materials as renewable resources: nonfood and industrial applications.

Wheat is currently the most important crop in the world in terms of yield, area under cultivation and geographical distribution (all continents and climatic zones except polar regions). It has achieved immense cultural and religious significance and, as pointed out by the authors of this volume, its price and availability have influenced the rise and fall of governments. The present volume should, therefore, be of wide interest as it provides a concise but comprehensive and well balanced account of the production and utilization of wheat, from sowing of the seed to processing of the harvested grain. The contents are divided into 10 chapters which fall into four neat sections. The first chapter introduces wheat as a crop, discussing its origin and outlining the different types and their end use characteristics. It then describes the morphology and development of the crop and introduces the wide range of production systems that are used. These range from intensive systems which are most widely used in Western Europe to reduced input systems which have been introduced over the past decade, driven largely by environmental and consumer concerns. This detailed introduction is followed by three chapters focusing on the characters that determine grain utilization and quality and how they are in turn influenced by the genotype and the environment (climate and nutrition). These lead logically into three chapters dealing with aspects of agronomy including sowing and crop establishment, nutrition and fertilizer use and management of pests and diseases. The latter includes detailed discussions of major fungal pathogens (e.g. mildews, rusts, Septoria, eyespot, take-all) and insect pests (aphids, flies, beetles) and of the control of broad leaved and grass weeds, but also covers viral and bacterial diseases, nematodes, molluscs and plant growth regulators used to control height (chlormequat and ethephon). Finally, three separate chapters consider the post harvest management of the grain including drying and pest control, the utilization of the vegetative parts of the crop as forage and the utilization of the grain for the distillation of alcohol and for fractionation into starch and gluten. Throughout the volume there is a major emphasis on optimising end use quality, reflecting the current competitive climate for growers and grain exporters. The level of coverage is designed to be suitable for undergraduate and postgraduate students in agronomy and I have little doubt that it will become a standard text for many courses. However, it is extensively referenced and will almost certainly be used more widely by lecturers and active research scientists. The authors are to be congratulated in producing an exceptionally attractive and readable volume which integrates a range of science from genetics through agronomy to food science.

A new steroid from safflower

Abstract A previously unreported steroid glycoside has been isolated from safflower meal. Spectral analysis of the steroid by MS, NMR, UV and IR reveals it to be a new structure of the form 15α,20β-dihydroxy-Δ 4 -pregnen-3-one.

Novel Neurospora crassa mutants with altered synthesis of polyunsaturated fatty acids

Five new mutants of Neurospora crassa that require supplementation with unsaturated fatty acids have been isolated. The mutants, designated pfa, are impaired in the synthesis of the polyunsaturated fatty acids α-linoleic or α-linolenic acid, but are able to synthesize oleic acid. The pfa mutants are thus distinct from previously described ufa mutants, which are unable to synthesize oleic acid. The five pfa mutants map to distinct loci, and have characteristic patterns of incorporation of [14C]acetate and [14C]oleate into their fatty acids.

Some chemical processes utilizing oleic safflower oil

Oleic safflower seed (UC-1) produces an oil containing approximately 80% oleic acid and 12% linoleic acid. The oil is a source of high quality oleic acid, and fatty acids from the oil may be used without further separation in some applications where technical oleic acid is now used, since oleic safflower free fatty acids have a a higher oleic acid content than good commercial grades of oleic acid. A high purity oleic acid can be produced by urea fractionation. Ozonization of the oil followed by reductive cleavage yields pelargonaldehyde and nearly colorless aldehyde oils. Ozonization of a crude mixture of oleic safflower acids followed by oxidative cleavage provides high yields of azelaic acid and pelargonic acid. In contrast, ozonization of free fatty acids from polyunsaturated vegetable oils produces azelaic acid and mixtures of lower molecular weight carboxylic acids with smaller amounts of pelargonic acid. Furtherore, ozone consumption is lower and reaction time is shorter when oleic safflower acids are used in place of more highly unsaturated fatty acids.

Nitrogen assimilation and partitioning in two nitrogen-fixing cultivars of Phaseolus vulgaris L.

Two cultivars of Phaseolus vulgaris L., one responsive (Mexico 309) and one less-responsive (Rio Tibagi) to nodulation with Rhizobium were grown in Leonard jars in a greenhouse. Bean plants were either inoculated with a strain of Rhizobium leguminosarum bv. phaseoli (UMR-1899), a vesicular-arbuscular mycorrhizal (VAM) fungus (Glomus etunicatum) or were left non-inoculated (controls). At two harvests (21 and 28 days post-emergence), extracts containing soluble proteins and free amino acids were prepared from leaves, roots and nodules of field beans. Nodulated plants contained a significantly higher concentration of protein and amino acids in all plant parts. Nitrogen-fixing beans invested a significantly greater proportion of total N as protein-N and amino acid-N as compared to VAM or control beans. Abundant nodule-specific proteins (nodulins) were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), identified and quantified using scanning densitometry. Rio Tibagi nodules contained a significantly lower concentration of glutamine synthetase (GS) subunits than did Mexico 309 nodules. Glutamate synthase (GOGAT) and GS activities were low relative to other legumes. The transferase/synthetase ratio for GS was also low indicating that the synthetase activity was caturated and was operating at maximal level in these young N2-fixing associations. Specific nodule activity (SNA) and the level of GS were correlated (r=0.90, p<0.05) for both cultivars at both harvests. GS activity was only 8 or 24% higher than SNA in nodules of Mexico 309 or Rio Tibagi cultivars, respectively, under conditions where substrate was not limiting. This suggests that early in the functioning of this symbiosis N assimilation by GS is the rate-limiting step in N2 fixation by these two bean cultivars, each with a different symbiotic efficiency. Phaseolus breeding programs that attempt to improve N2 fixation in beans should identify germplasm that expresses elevated levels of nodule-specific GS or GOGAT, and this material should be used along with effective R. leguminosarum bv. phaseoli strains that have already been selected, to determine superior host-microsymciont associations.