Showing papers by "Agriculture and Agri-Food Canada published in 1988"

Reference values of blood parameters in beef cattle of different ages and stages of lactation.

Abstract: Reference (normal) values for 12 blood serum components were determined for 48 Shorthorn cows (2-10 years old) and their 48 calves, 357 crossbred cows (12-14 years old), 36 feedlot bulls and 36 feedlot steers. In addition, hemoglobin, hematocrit, triiodothyronine, thyroxine and cortisol levels were determined for the crossbred cows, and feedlot bulls and steers. Reference values were tabulated according to sex, age and stage of lactation. Serum concentrations of urea, total protein and bilirubin, and serum activity of aspartate aminotransferase and lactate dehydrogenase increased with age (P less than 0.05), while calcium, phosphorus and alkaline phosphatase decreased with age (P less than 0.05) from birth to the age of ten years. The Shorthorn cows had the highest levels of glucose at parturition (P less than 0.05) with decreasing levels during lactation. Creatinine concentration decreased during lactation and increased during postweaning. Both lactate dehydrogenase and aspartate aminotransferase levels increased (P less than 0.05) during lactation. Urea and uric acid were present at higher concentrations in lactating than nonlactating cows (P less than 0.05). The values reported, based on a wide age range and large number of cattle, could serve as clinical guides and a basis for further research.

Direct drilling and soil loosening for spring cereals on a fine sandy loam in Atlantic Canada

Abstract: Changes in soil structure and properties, plant growth and diseases and agronomic aspects were determined, after 3 years, on a Charlottetown fine sandy loam, an Orthic Podzol with a perhumid soil moisture regime, subjected to three tillage systems for spring cereals. The tillage systems consisted of direct drilling, soil loosening with a “paraplow” followed by direct drilling and mouldboard ploughing. Rate of plant growth and other crop measurements were not changed by the tillage systems, except for the depth of seeding. Direct drilling reduced the accumulation of N and K in the plant, and reduced grain N, compared with mouldboard ploughing. Soil loosening prior to direct drilling prevented the decline in N and K accumulation, and increased grain yield and N content, in comparison with mouldboard ploughing. Direct drilling caused changes in soil macro-aggregation and reduced the evaporation rate, and increased microbial biomass C and N, total organic C and N and extractable ions at the soil surface (0–5 cm), compared with mouldboard ploughing. In addition, earthworm numbers were increased under direct drilling. Root lesion and spiral nematodes were not influenced by tillage differences. Soil loosening prior to direct drilling alleviated the significant reductions in soil macroporosity, and prevented the increase in soil bulk density, soil strength and percentage water-filled pore space (%WFPS) associated with direct drilling alone. Although soil permeability was optimum under direct drilling alone, the relative increase in %WFPS and reduction in soil aeration were associated with a concomitant increase in common root rot.

Chemotaxis by Pseudomonas syringae pv. tomato.

Abstract: Optimal laboratory conditions for studying chemotaxis by Pseudomonas syringae pv. tomato were determined by using the Adler capillary tube assay. Although they are not an absolute requirement for chemotaxis, the presence of 0.1 mM EDTA and 1 mM MgCl(2) in the chemotaxis buffer (10 mM potassium phosphate [pH 7.2]) significantly enhanced the response to attractant. The addition of mannitol as an energy source had little effect. The optimal temperature for chemotaxis was 23 degrees C, which is 5 degrees C below the optimal growth temperature for this pathogen. The best response occurred when the bacteria were exposed to attractant for 60 min at a concentration of approximately 5 x 10 CFU/ml. P. syringae pv. tomato was strongly attracted to citric and malic acids, which are the predominant organic acids in tomato fruit. With the exception of asparagine, the major amino acids of tomatoes were weak to moderate attractants. Glucose and fructose, which account for approximately 47% of tomato dry matter, also elicited poor responses. In assays with tomato intercellular fluid and leaf surface water, the bacterial speck pathogen could not chemotactically distinguish between a resistant and a susceptible cultivar of tomato.

Factors influencing the efficacy and economic returns of aerial sprays against the wheat midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae)

Abstract: Evaluations of individually collected wheat heads and whole plants indicated that several factors may influence the efficacy of aerial sprays against the wheat midge, Sitodiplosis mosellana (Gehin). These factors related to methods of assessing midge damage, condition of wheat heads during spraying, and methods of spray application. Location- and distribution-related influences also were important.Efficacy assessments were based on reductions in midge larvae, midge-damaged kernels, and percentage kernel damage. The latter data were confounded by differences in kernel numbers within wheat heads. In head and plant samples, sprays were more effective at reducing numbers of midge larvae than reducing the incidence of midge-damaged kernels. Evaluations of individual heads overestimated the efficacy of sprays in whole plants which contained one primary and two tiller heads. Sprays provided more effective midge control and kernel protection in the primary heads, which emerged before spraying, than tiller heads, which emerged mainly after spraying. Protection was usually better in apical than basal regions of each head type. In whole plants, efficacy declined as tillering increased.Plant evaluations indicated that the high-volume (37.4 L water per hectare) chlorpyrifos spray provided the best midge control and kernel protection (95% and 87%, respectively), followed by the low-volume (18.7 L water per hectare) chlorpyrifos spray (87% and 76%, respectively), and low-volume dimethoate spray (66% and 53%, respectively). When improvements in both yield and grade were considered and calculations based on 1987/1988 wheat prices, net returns from the three aerial sprays ranged from 113 Canadian per hectare. Long-term benefits of the sprays probably were less favourable. Reduction in wheat midge after spraying would negate the benefits of an egg–larval parasite, Pirene penetrans (Kirby), which was present in low numbers.

Evaluation of insecticides for protection of wheat against damage by the wheat midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae).

Abstract: The efficacies of cypermethrin, deltamethrin, permethrin, endosulfan, methoxychlor, carbofuran, chlorpyrifos, dimethoate, and malathion were evaluated against the wheat midge, Sitodiplosis mosellana (Gehin). Methods are described for evaluating damage and protection in individually collected wheat heads and whole plants. Weighted values from whole plants provided the best indication of kernel protection and yield response.Whole plants contained three main types of wheat heads (primary heads, first tillers, and second tillers) which differed in their frequencies, kernel numbers, and developmental times. The latter indicated that the chronology of midge attack, status of midge infestations during spraying, and spray coverage also differed in the head types.Insecticides provided different levels of kernel protection within and among the various head types. The majority of primary heads emerged before spraying and harbored midge eggs at spraying. In these wheat heads, chlorpyrifos, endosulfan, and malathion provided significantly better kernel protection (60–75%) than permethrin, deltamethrin, and cypermethrin (<7%). The results suggested that the more effective kernel protectants permeated the spikelet and controlled the eggs and/or newly hatched larvae. Kernel protection in the primary heads was closely related to insecticide volatility. Conditions were different in most first tillers and second tillers which emerged after spraying. In these wheat heads, poor spray coverage and short residual activity against adult midge appeared to limit kernel protection by all insecticides.

Isolation of Aspergillus parasiticus speare and Beauveria bassiana (Bals. Vuillemin) from melanopline grasshoppers (Orthoptera: Acrididae) and demonstration of their pathogenicity in Melanoplus sanguinipes (Fabricius)

Abstract: Description de l'isolement de deux champignons pathogenes sur des criquets et evaluation de leur pathogenicite sur M. sanguinipes a l'etat nymphal, par application de quantites variables de conidies par individu par voie topique, orale ou par injection

Nitrogen fixation in bambara groundnut, Voandzeia subterranea (L.) Thouars

Abstract: To improve biological nitrogen fixation in bambara groundut (Voandzeia subterranea (L.) Thouars), the relative effectiveness of 24 cultivars was studied in the field at two experimental stations selected for their different ecological conditions. Thirty oneRhizobium strains were isolated and 12 cultivars were screened during this study. Both indigenous and introduced NiftalRhizobium strains were used during a second study on host cultivars xRhizobium strains interactions. Nodulation index and shoot dry weight were used to assess the efficiency. The widest effectiveness spectrum was observed with the indigenous strain MAO 113 and the introduced strain TAL 22.

Sylvatic trichinosis in Canada.

Abstract: Pepsin digestion of musculature from 2253 animals revealed that sylvatic trichinosis occurred in various species of mammals from the eastern to the western Arctic and extended down into the Rocky Mountain and Foothills regions of western Canada. Infections were demonstrated in Arctic fox, red fox, wolf, raccoon, coyote, lynx, bobcat and dog.

Thrips (Thysanoptera) in canola crops in Saskatchewan

Abstract: Adults of nine species of thrips were collected from canola fields: Aeolothrips fasciatus (L.), Anaphothrips obscurus (Muller), Frankliniella occidentalis (Perg.), Frankliniella tritici (Fitch), Limothrips denticornis Haliday, Odontothrips loti (Haliday), Thrips nr. fuscipennis Haliday, Thrips tabaci Lindeman, and Thrips vulgatissimus Haliday. Of these, F . tritici was the most abundant in the collections and appears to have the greatest potential to be a significant canola pest, followed by T . tabaci and T . vulgatissimus .

Effect of low temperatures on mortality of grasshopper eggs (orthoptera: acrididae)

Abstract: Mortality of grasshopper eggs on the Canadian prairies is brought about by many factors, including winter temperatures. Although several authors (Parker 1930; Pickford 1966, 1976; Riegert 1967) have reported that winter temperatures can affect the mortality of grasshopper eggs, no quantitative data have been presented. This note reports the relationship between low temperatures and grasshopper egg mortality

Identification of oat-adapted isolates of cereal Septoria in the UK using a detached leaf technique

Abstract: Isolates of Septoria spp. from cereals were tested for their relative pathogenicity to detached seedling leaves of three cereal species. Each of 23 isolates showed unequivocal adaptation to either oats, or wheat, or barley. Five oat-adapted isolates were from Prince Edward Island, Canada, where S. avenue is prevalent on oats; three were from the UK, where there are few oat crops and where adaptation to oats has not been reported. Oat-adapted isolates tended to have pycnidiospores of above-average length and could be referred to S. avenae. Wheat-adapted and most barley-adapted isolates had shorter spores and could be referred to S. nodorum. UV-fluorescent pigment was produced on oxgall agar by all wheat-adapted isolates, but only by a minority of oat-adapted and barley-adapted isolates. It is suggested that adaptation to cereal species is a more useful character than spore length for classifying isolates.

Ammonification and nitrification of N in acid soils at 26 field sites one year after liming

Abstract: The objective was to determine the effect of liming on the net ammonification and nitrification in the field of 26 acid soils during the first year after application. The soils ranged from pH 4.4 to 6.0 and were limed to a target pH of 6.7. The 26 sites were located in Alberta and northeastern British Columbia. Soils were limed in the spring, fallowed and sampled in the next spring. The content of NH4 +‐N plus NO3 ‐‐N in the 0–15 cm layer of the non‐limed treatments varied from 6 to 48 Hg/g (average of 26), while the limed treatment varied from 14 to 89 μg/g (average of 40). The increase in ammonification was negatively related to soil pH and positively related to soil total N (R=0.66**). The proportion of NH4 +‐N in the mineral‐N varied among the non‐limed samples, but it was not related to soil pH. The same was true among the limed samples. This field study suggests that for at least a year after liming both the increase of mineral‐N, and variation in nitrification, may complicate crop behavior...

Selection response and efficiency of doubled-haploid recurrent selection in a cross-fertilized species

Abstract: Computer simulation was used to compare the simulated response to doubled-haploid (DH) mass selection with the response predicted by mathematical formulae. The efficiency of DH versus diploid mass selection in a cross-fertilized species was also studied by means of theoretical consideration and computer simulation. Simulated gain was in agreement with the predicted gain in the DH population under both additive and complete dominance models. The simulated variance of response to DH mass selection was close to the predicted variance at both the 5% and 25% selection regimes under additive and complete dominance models. The efficiency of DH over diploid mass selection was shown to be dependent upon the allelic frequency, the degree of dominance, and the amount of environmental variance. In theory the efficiency can range from zero to infinity, but in reality it should be greater than one. The efficiency ranges from √2 to 2 in the absence of dominance; it can be greater than two only in the presence of dominance and a small environmental variance. The variance of response to DH mass selection can be smaller than or up to twice as large as the variance of response to diploid mass selection. Computer simulation results agreed with the predicted efficiency of DH mass selection and with the predicted variance-of-response ratio of DH mass selection to diploid mass selection.

Plant Pathogenic Mycoplasmas: Morphological and Biochemical Characteristics

Abstract: Association of wall-less prokaryotes with plants was first reported by Japanese workers in 1967 (13,23). This association has since been reported for more than 100 diseases inflicting damage to a variety of crops of agricultural importance throughout the world (29). Almost all such diseases are disseminated in nature by means of insect vectors, the leaf-hoppers (Cicadel1ids), in a persistent manner. The pathogen undergoes multiplication in both vectors and host plants (51). Most of these diseases were presumed to be caused by viruses in spite of the fact that the causal agents were never morphologically identified. Several of these organisms have not yet been cultured in cell-free medium and are termed as mycoplasma-like organisms (MLOs). These microbes are pleomorphic and wall-less, morphologically and ultrastructurally resembling non-helical mycoplasmas. These are located in the sieve tubes of plants showing symptoms such as leaf yellows, leaf dwarfing, leaf mottling, flower dwarfing, flower virescene, witches’ broom, shortening of internodes, stunting etc.

Purification and Properties of Mycoplasma-Like Organisms from Diseased Plants

Abstract: Organisms resembling Mycoplasma (Class Mollicutes), first implicated by Japanese workers as the etiological agents of some “yellows” group of plant diseases (6,10), have been shown to be associated with many diseases that inflict damage to a variety of crops of economic importance (11,12). Most of these pleomorphic microbes are non-helical and are commonly referred to as mycoplasma-1ike organism(s) (MLO) because they have not yet been characterized through cultivation in a cell-free medium. Mycoplasmal etiology of about 100 plant diseases still remains to be demonstrated because Koch’s postulates cannot be satisfied. However, a few plant pathogenic mycoplasmas have been cultured in vitro, Koch’s poltulates fulfilled, and placed in a new genus Spiroplasma because they produce helical and motile filaments (7,14,15). Rapid progress has since been made on immunological, microbiological, biochemical, biophysical, and ultrastructural characterization of these mycoplasmas, especially of S. citri -- the etiological agent of citrus stubborn disease (1,3, 5,13,29,30).