Crop Rotation Effects on Population Densities of Ectoparasitic Nematodes

The influence of rotation crop species on population densities of ectoparasitic nematode species common to soybean and corn fields of the North-Central region of the USA was studied for 5 years in 16 field blocks rotated to corn, soybeans, oats, wheat, and forage mixtures. Each block was sampled each year between mid-July and mid-August. High populations of Helicotylenchus pseudorobustus were maintained in all crops, especially corn. Tylenchorhynchus martini and Xiphinema americanum also developed with all crops, but a second year of corn depressed densities of both species. Paratylenchus projectus densities were high on soybeans and on forage consisting primarily of legumes.     

Rates of rhizodeposition and ammonium depletion in the rhizosphere of axenic oat roots

Summary A multiple split root chamber and artificial soil were developed which allowed for maintenance of axenic conditions and for the isolation of soil from specific regions of single roots. A sterile minirhizotron was used to measure patterns and rates of root extension under sterile conditions. Carbon and nitrogen distributions in the rhizosphere of sterile oat roots were measured in combination with rates of root elongation to calculate specific rates of rhizodeposition and ammonium nitrogen uptake. The highest rates of rhizodeposition C production and N depletion occurred at the root tip (first day segment). Rhizodeposited soluble and insoluble C compounds represented up to 50% of the standing root biomass C. Within 48 hours after root entry, levels of rhizosphere ammonium-N decreased by 40–50%. The results were summarized in a simple model of root growth, rhizodeposition, and NH ₄ ⁺ −H uptake. From a dissertation by the senior author submitted to the Academic Faculty of Colorado State University in partial fulfillment of the requirements for the Ph.D. degree.     

Analysis of a cDNA encoding arginine decarboxylase from oat reveals similarity to the Escherichia coli arginine decarboxylase and evidence of protein processing

Summary Arginine decarboxylase is the first enzyme in one of the two pathways of putrescine synthesis in plants. We purified arginine decarboxylase from oat leaves, obtained N-terminal amino acid sequence, and then used this information to isolate a cDNA encoding oat arginine decarboxylase. Comparison of the derived amino acid sequence with that of the arginine decarboxylase gene from Escherichia coli reveals several regions of sequence similarity which may play a role in enzyme function. The open reading frame (ORF) in the oat cDNA encodes a 66 kDa protein, but the arginine decarboxylase polypeptide that we purified has an apparent molecular weight of 24 kDa and is encoded in the carboxyl-terminal region of the ORF. A portion of the cDNA encoding this region was expressed in E. coli, and a polyclonal antibody was developed against the expressed polypeptide. The antibody detects 34 kDa and 24 kDa polypeptides on Western blots of oat leaf samples. Maturation of arginine decarboxylase in oats appears to include processing of a precursor protein.     

Organization of repeated sequences in species of the genus Avena

Summary Four repetitive sequences from Avena murphyi have been isolated and their genome organization studied in different species of the genus Avena. A tandem sequence array was found for the Avena species that contain the C genome. Three other dispersed sequences present in the A and C genomes were arranged in a genomespecific manner. The fact that no major differences in the hybridization patterns were found between species with the same basic genome is consistent with the current taxonomy of Avena species.     

The influence of lead,cadmium, and nickel on the growth of ryegrass and oats

Summary A 2⁴ factorial experiment was conducted under greenhouse conditions. Factors and levels in the experiment were soil pH at 4.5 and 6.4, and cadmium, lead, and nickel added to the soil to provide soil concentrations of 50, 250, and 50 ppm, respectively, above background levels. Two species were grown in succession in the same experimental pots. Ryegrass (Lolium hybridum Hausskn. cv. Tetrelite) was harvested three times and then one crop of oats (Avena sativa L. cv. Garry) was grown and harvested. Plant tissue concentrations of cadmium, lead, and nickel were monitored throughout the experiment.Addition of cadmium to the soil lowered the dry matter yields in all three ryegrass harvests and also reduced the yield of oat grain. The application of lead nitrate to the soil enhanced the yield of ryegrass obtained at the first harvest and also increased the yield of oat grain. Nickel, added to the soil at 50 ppm, was relatively innocuous to ryegrass and oats.The presence of added cadmium, lead, or nickel to the soil resulted in enhanced tissue concentrations of these metals in both ryegrass and oats. This effect was particularly enhanced by a soil pH of 4.5. A single exception to this observation was that lead was not detected, under any of the conditions of this experiment, in oat grain.The presence of lead in the soil enhanced cadmium concentrations in ryegrass tissues. The presence of cadmium in the soil decreased lead tissue concentrations in ryegrass and oat straw. Soil pH interacted with both nickel and lead in the second ryegrass harvest with subsequent changes in tissue cadmium concentrations. At a soil pH of 4.5, the presence of added lead or nickel to the soil significantly increased the ryegrass tissue cadmium concentration beyond that observed at a soil pH of 6.4 with or without enhanced nickel or lead concentrations.     

Structural characteristics and rheological properties of partially hydrolyzed oat β-glucan: the effects of molecular weight and hydrolysis method

Partial hydrolysates of (1→3)(1→4)-β- -glucan from oats were produced by three hydrolysis methods: acid, cellulase or lichenase. The molecular weights ranged from 31 000 to 237 000 g/mol. Six percent solutions of small molecular weight β-glucans formed elastic gels after 4 days at 4 °C whereas larger molecular weight β-glucans remained viscous liquids after 7 days. The melting temperature of the gels increased as they aged and the peak heat flow temperature, measured by differential scanning calorimetry, was 62±2 °C. Partial hydrolysates produced with cellulase, which was shown to preferentially cleave regions of the molecule with longer contiguous β-(1→4)-linked -glucopyranosyl units, tended to produce more elastic gels with stronger junction zones than partial hydrolysates produced with lichenase which cleaves the β-(1→4) glycosidic 3-o-substituted glucose links. This suggests that β-(1→3)-linked cellotriose sections of the polymer are probably the segments which form the junction zones in the gel network rather than cellulose-like segments.     

Identification of the 21 monosomic lines in Avena byzantina C. Koch cv. ‘Kanota’

Summary All of the 21 possible monosomic lines have been screened and confirmed from 33 monosomic stocks of Avena byzantina C. Koch cv. Kanota. All of them, except Mono-21 which was a progeny of monosomic Cherokee (A. sativa) repeatedly backcrossed with Kanota, were obtained in the progenies of haploid (2n = 3x), aneuploid (2n = 6X±) and autotriploid (2n = 9X) partners of twins. Identification of the monosomics was carried out by means of the double monosomic method, monosomic analysis on marker genes, leaf peroxidase isozyme analysis, karyotype analysis and nullisomic analysis. The monosomic lines were numbered from Mono-1 through to Mono-21, mainly in the order of monosome length from the longest to the shortest. Most monosomic lines were hardly distinguishable by morphological characteristics from each other or from normal disomics. In the selfed progenies of four monosomic lines, Mono-8, -9, -17 and-19, segregation of nulli-, mono- and disomics was observed, but no nullisomics were found in the other lines. In most cases the frequency of monosomics ranging from 35.5 to 97.8% was, compared to those of nulli- and disomics, highest in the selfed progeny of monosomics. The monosomic lines were easily maintained and can be used for genetic analysis because of their good seed fertility and high monosome transmission rate. They have the near isogenic background of Kanota.     

Evaluation and control of the nutritional status of cereals

Summary Based on grain yield and the chemical composition of grain and straw at maturity, a quantitative method of estimating the nutritional status of the young plant and the corresponding nutritional conditions of the growth medium was developed from results of three years' of factorial fertilizer pot experiments with oats and spring wheat.In trophogenetic methods, yield and chemical composition of older plants form the basis for the conclusion on soil fertility at sowing time with the aim to decide on future fertilizer policy.Contrary to earlier trophogenetic methods, the present method includes the nutritional status of the young plant—based on a well-defined stage of development (DMw-level) and pure-effect concentrations of nutrients—as an intermediate link in the above conclusion.The method follows the reversed direction of procedures based on the models used for diagnosis and prognosis of grain yield and chemical composition of plant parts at maturity previously outlined.The reliability of the method was proved by comparing trophogenetically determined and experimentally obtained nutrient concentrations in the young plant. The coefficients of regression and correlation were both close to 1, and the latter was highly significant.Together with the methods of diagnosis, prognosis and therapy, trophogenesis completes the framework enclosing all possibilities of using the plant analysis in evaluation and control of the nutritional status of the plant.     

Effect of farm yard manure and iron on dry matter yield and nutrients uptake by oats (Avena sativa)

A pot culture experiment was conducted on a loamy sand soil to study the effect of FYM and Fe on dry matter yield and uptake of nutrients by oats (Avena sativa) crop in green-house. Application of Fe @ 5 and 20 ppm increased dry matter yield by 5.11 and 11.55 per cent, respectively. The per cent increase in dry matter yield over control with the application of 0.5 and 1.0 percent FYM was 19.06 and 30.07, respectively. Application of FYM increased concentration and uptake of P significantly. Phosphorus uptake increased by 23.60, 54.38, 91.01 and 134.61 per cent over control with 0.5, 1.0, 2.0 and 4.0 per cent FYM, respectively. Phosphorus concentration decreased at 20 ppm Fe but uptake increased significantly at 5 ppm Fe. Concentration and uptake of Ca increased with increasing amounts of Fe and application of FYM decreased concentration of Ca but uptake increased upto 1.0 per cent FYM over control. The Mg concentration and uptake decreased significantly with increased amount of Fe. Application of FYM also decreased Mg concentration but its uptake increased upto 1.0 per cent FYM and then decreased.Iron concentration and uptake increased upto 2 per cent FYM and then decreased. Whereas concentration of Fe decreased with increased amount of applied Fe but its uptake increased nonsignificantly with increased amount of added Fe.Managenese concentration and uptake decreased significantly with increased amount of applied Fe. Managenese concentration increased upto 0.5 per cent FYM but its uptake continued increasing with increasing amounts of applied FYM.     

Effect of farm yard manure and CaCO3 on the dry matter yield and nutrient uptake by oats (Avena sativa)

A pot culture experiment was conducted in loamy sand soil to study the effect of different levels of FYM and CaCO₃ on the dry matter yield and nutrients uptake by oats. Application of different levels of CaCO₃ (0, 2, 4 and 8%) and FYM (0, 0.5, 1,2%) resulted in significant increase in dry matter yield of oats. But, a little decrease in dry matter yield was obtained at 4% FYM. The interaction of FYM×CaCO₃ was also significant on dry matter yield of oats. There was a significant decrease in the concentration and uptake of P with increased levels of applied CaCO₃. But, application of FYM resulted in a significant increase in concentration and uptake of P. A significant increase in concentration and uptake of Ca was observed with the increasing levels of CaCO₃. The concentration of Ca decreased with the increased application of FYM in the presence as well as in the absence of added CaCO₃. However, at 0.5 and 1.0 percent FYM with 4 per cent CaCO₃ a little increase in Ca concentration was recorded. The Mg concentration in oat decreased significantly with the increasing levels of CaCO₃ and FYM. The effect of CaCO₃ levels was more pronounced in the absence as well as in the presence of FYM. The Mg uptake followed a different pattern. At 0 and 2% CaCO₃ and application of FYM @ 1 per cent the Mg uptake increased but then it decreased with increasing levels of FYM and CaCO₃ both alone as well as in the presence of each other. The concentration and uptake of Mn decreased with increasing levels of applied CaCO₃. However, in the absence of CaCO₃, the application of FYM increased the concentration and uptake of M_n in oats. In the presence of CaCO₃, Mn concentration decreased at all levels of FYM application but at 8 per cent CaCO₃ there was a slight increase in Mn concentration with 0.5, 2 and 4 percent FYM. Iron concentration and uptake was also affected adversely by increasing levels of CaCO₃ but FYM application removed the harmful effect of CaCO₃ to some extent.