Agriculture and Agri-Food Canada, Research Centre, Lethbridge, AB, Canada T1J 4B1
A healthy riparian ecosystem functions as both filter and a reservoir, affecting both water quality and pattern of delivery of water to downstream users. The processes which affect ecosystem function are closely related to the vegetation within the riparian zone. This ecosystem is usually very productive, that makes it desirable for agricultural production. However, agricultural activity can compromise the water resource by modifying the vegetation and through contamination with chemicals or animal waste. Riparian ecosystems can be degraded through agricultural activity but also enhanced or constructed with appropriate technology.
The great importance of riparian ecosystems to society led to the organization
of a symposium entitled 'Effects of Agriculture on the Riparian Ecosystems'
in conjunction with the 1996 Agricultural Institute of Canada annual meeting
held in Lethbridge, AB. It was organized and sponsored by representatives
of the Canadian Society of Agronomy with presenters from the prairie provinces
and Ontario. The purpose of the symposium was to facilitate the exchange
of information among researchers, land managers, and the public on managing
agricultural impacts to protect the water resource. From the four presentations
given, three were eventually accepted after peer review. Two papers deal
with livestock grazing within contrasting environments - one on pasture
in Ontario and the other on Alberta rangeland, and the third paper deals
with constructed wetlands.
Crop Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1
The potential for impact by grazing livestock on unprotected watercourses may vary with climate, with landscape level fators including the landform within which the pasture is located, with the biophysical characteristics of the watercourse itself, and with pasture and grazing management practices. Policies seeking to implement cost-effective measure to protect downstream water quality need to acknowledge large- as well as small-scale processes which can moderate of exacerbate potential sources of pollution. Applied and scholarly evidence suggest that unrestricted livestock access accounts for a relatively modest share of watercourse pollution in humid temperate regions, as compared with such watershed-specific factors as leaking septic tanks and confinement feeding systems.
A wide variety of evidence suggests that the degree of compatability of grazing livestock with a healthy riparian ecosystem should be viewed as an hypothesis that is testable on a site-specific basis. Greater understanding of the factors causal to livestock behavior in, and impact on, watercourses may help to better focus preventative and remediation efforts by both producers and policymakers.
Key words: Riparian ecosystem, beef cattle, pasture fertility, soil and water conservation
1Regional Head, Fisheries Management Division, Alberta Environmental Protection, Lethbridge, T1J 4C7; 2Regional Range Manager, Public Lands Branch, Alberta Agriculture, Food and Rural Development, Lethbridge, T1J 4C7
Our paper provides an ecological perspective on the interrelationship between livestock grazing and riparian areas through a review of topical literature. We also describe the Alberta Riparian Habitat Management Project (also known as 'Cows and Fish'), and draw upon our experience to provide a perspective on future riparian management actions. Those actions should begin with an understanding that prairie landscapes evolved with herbivores, in a grazing regime timed and controlled by season and climatic fluctuations where grazing by native grazers was followed by variable rest periods. Prevailing range management principles represent an attempt to imitate the natural system and describe ecologically based grazing systems. Traditionally, range management guidelines have focused on grazing practices and impacts in upland, terrestrial rangelands, with a lack of attention devoted to riparian areas.
Three decades of riparian investigation has quantified the effect unmanaged livestock grazing can have on range productivity and watershed function. We contend that suitable grazing strategies for riparian areas will be developed first by understanding the function of riparian systems and then by applying range management principles to develop riparian grazing strategies. A key step towards determining the fit of livestock grazing is an understanding of the formation of riparian systems and their ecological function. We describe riparian structure, function and process, to provide linkages between livestock grazing, riparian vegetation health and stream channel dynamics. We summarize the effects of unmanaged livestock grazing on riparian habitats and fish and wildlife populations. The general conclusion is that unmanaged grazing results in overuse and degradation of riparian areas. The literature provides several options for the development of riparian grazing strategies. We provide an overview of strategies suitable for riparian areas in Southern Alberta which should maintain ecological function and sustained use.
Water Research Corp., 11 Innovation Blvd., Saskatoon, SK, Canada S7N 3H5 hans.Peterson@sk.sympatico.ca
Constructed wetlands are emerging as a serious challenge to conventional wastewater treatment because of lower construction and operating costs, less requirement for trained personnel, more flexibility, and lower susceptibility to variations in waste loading rates. Water quality improvements can be achieved by removal of plant nutrients, such as N and P, organics (natural and man-made) as well as inorganic contaminants. Wetland treatment is now advocated by regulatory agencies and has been determined as the technology of choice by municipalities and industries required to meet stringent discharge regulations. These same regulations have not usually been imposed on the agricultural community, but deteriorating water sources will likely change this regulatory anomaly. Use of this technology in treating agricultural wastewater is still in its infancy with few, although rapidly expanding, applications. This paper aims to highlight different aspects of wetland treatment by exploring its use for the treatment of agricultural run-off as well as wastewater from the agri-food industry. It is concluded that natural wetlands will be quite limited in absorbing agricultural wastewater while constructed wetlands can be designed for optimum pollutant removal.
Key words: Constructed wetlands, wastewater
treatment, agriculture, food processing,
nutrient removal, nitrogen, phosphorus, organics
1Département de Phytologie, Université Laval, Québec, Canada G1K 7P4; 2Soils and Crops Research and Development Centre, Agriculture and Agri-Food Canada, Sainte-Foy, Canada G1V 2J3
An interspecific wheat × triticale hybridization program was initiated with the scope of widening and improving the winter wheat gene pool. However, progress was hampered by severe necrosis that caused the death of F1 hybrids from crosses between the most winterhardy wheat and triticale cultivars. This paper describes hybrid necrosis as the main barrier to gene transfer between winter wheat cultivars Borden, Augusta and Ruby, and hexaploid winter triticales OAC Wintri and K9--6. Crosses with tester lines revealed that the three winter wheats were carriers of the necrotic Ne2 allele. High temperature (30°C) treatment until heading stage permitted to only partially circumvent the problem. A study of cross direction effects at the backcross level showed that the conventional method (F1 × wheat) was more efficient for plant recovery, but plants produced by the alternative backcross system (wheat × F1) were more self-fertile. Within the most winterhardy germplasm, hybrid necrosis is a major problem for transferring genes between winter wheat and triticale.The use of non-necrotic winter wheat lines such as MC11N, a local winter wheat selection, may have a special value as a bridge to circumvent the necrosis problem.
Key words: hybrid necrosis, Ne genes, wheat × triticale hybrids, cross direction.
1Grain Research Laboratory, Canadian Grain Commission, 1404-303 Main Street, Winnipeg, Manitoba, Canada R3C 3G8; 2Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, Ottawa, Ontario, Canada K1A 0C6; 3PEI Grain Elevators Corporation, P. O. Box 250, Kensington, Prince Edward Island, Canada C0B 1M0; 4Alberta Pool, P. O. Box 2700, Calgary, Alberta, Canada T2P 2P5; 5Research Station, Agriculture and Agri-Food Canada, P. O. Box 3000 Main, Lethbridge, Alberta, Canada T1J 4B1; 6Research Centre, Agriculture and Agri-Food Canada, Charlottetown, Prince Edward Island, Canada C1A 7M8.
Kernel colour is an important marketing trait for both malting and feed barleys. Therefore a study was initiated to investigate the kernel colour of 75 Canadian barley (Hordeum vulgare L.) cultivars at three locations (Charlottetown, Ottawa, and Bentley) across Canada in 1991 and 1992. Kernel colour was measured by an Instrumar Colormet Spectrocolorimeter. Kernel colour was found to be brighter at the two locations in eastern Canada (Charlottetown and Ottawa) than at the location in western Canada (Bentley). Two-row cultivars on average were more discoloured than six-row cultivars; eastern two-row were more discoloured than western two-row. Covered barleys were less discoloured than hulless barleys in five of the six environments, but covered barleys at Bentley in 1992 were more discoloured than hulless barleys. Kernel discolouration appeared to be associated with susceptibility to net blotch for six-row cultivars. More studies are needed on kernel discolouration of barley.
Key words: barley, Hordeum vulgare, kernel colour
1Plant Science Department, Nova Scotia Agricultural College, Truro, Nova Scotia, Canada B2N 5E3, rmartin@cox.nsac.ns.ca; 2Math and Physics Department, Nova Scotia Agricultural College, Truro, Nova Scotia, Canada B2N 5E3, t.astatkie@nsac.ns.ca; 3Animal Science Department, Nova Scotia Agricultural College, Truor, Nova Scotia, Canada B2N 5E3, jcooper@imail.nsac.ns.ca
Soybean intercropped with corn can produce a high quality silage but pods of early maturing soybean varieties usually shatter when harvested, thus reducing the silage protein potential. In 1991 and 1992, an experiment was conducted in Truro, Nova Scotia and Sussex, New Brunswick to determine whether later soybean varieties can provide sufficient biomass and protein in intercrops and escape pod losses at harvest. Early, early high protein, medium, late and very late maturing varieties of soybean were grown as monocrops and intercrops with corn. Eight response variables were measured: soybean shoot biomass yield, intercrop shoot biomass yield, soybean shoot protein concentration, intercrop shoot protein concentration, soybean shoot protein yield, intercrop shoot protein yield, soybean seed biomass yield and soybean seed protein concentration. The two later soybean varieties yielded higher than the two early varieties, contributing to higher protein yields in the later varieties than in the early varieties, under both monocropping and intercropping. In contrast to the corn monocrop, intercrops with all soybean varieties produced higher protein concentrations. Under intercropping, only late variety produced significantly higher protein yields that the corn monocrop, however none of the varieties resulted in significantly lower biomass yields than the corn monocrop. With the late soybean variety, land equivalent ratios of the intercrop shoot biomass yield and the intercrop shoot protein yield revealed yield advantages of intercrops over monocrops of 21% and 10% respectively. The late variety resulted in an increased intercrop shoot protein concentrations without reducing the intercrop shoot biomass yield, because it was still green enough to be harvested with minimal pod shattering.
Key words: Soybean variety, corn-soybean intercrop, biomass, silage protein
1National Institute of Agricultural Research, P.O. Box 589. Settat, Morocco; 2Department of Soil and Crop Science, Colorado State University, Fort Collins, CO. 80523, USA; 3Faculté des Sciences Mohammedia Ben M'sik, Université Hassan II, Casablanca, Morocco
One of the common features of the Mediterranean climate in North Africa is the uncertainty of rainfall immediately after wheat (Triticum durum Desf) emerges. Relatively little work has been done to compare the drought resistance of spring durum wheat cultivars under early-season drought stress. There is a limited insight into the physiological basis of spring durum wheat drought resistance in rainfed Mediterranean regions. Field experiments were conducted in 1995 and 1996 growing seasons, and a greenhouse experiment was conducted in 1996 to examine differences in some physiological characters among six spring durum wheat cultivars in response to different durations of early-season drought, and rewatering; and to determine the relationships of these characters to drought resistance. Six spring durum wheat cultivars were evaluated under four water regimes. Water regime treatments were: a well-irrigated treatment; and three water deficit treatments imposed during the period from emergence through either the onset of tillering, mid-tillering or the end of tillering. Cultivars differed widely in their response to early season water stress. Under drought stress conditions, grain yield, above-ground dry matter yield, water use efficiency for the grain (WUEg) and for the total dry matter (WUEdm) were strongly positively associated with net CO 2 uptake:transpiration ratio (A/E), and osmoregulation capacity. It is concluded that drought-induced changes in A, A/E, stomatal resistance, and osmotic adjustment are possible key control points in determining the drought-resistance of a cultivar. Furthermore, there is a substantial degree of intraspecific variation for the above mentioned physiological attributes to explore as a selection tool. Selection for high osmoregulation capacity and high A/E ratio would seem to be a justifiable means of improving total dry matter and grain yield under conditions of early-season water stress.
Key Words: Wheat, Triticum durum Desf., Physiological attributes, Early-season drought.
1Agriculture and Agri-Food Canada, Research Centre, 6000 C & E Trail, Lacombe, Alberta, Canada T4L 1W1; 2Canadian Grain Commission, Grain Research Laboratory, 1404-303 Main Street, Winnipeg, Manitoba, Canada R3C 3G8
Several reports have indicated that oat beta-glucans may play an important role in reducing the incidence of degenerative diseases in humans. However, very little information has been published on the inheritance of beta-glucan concentration in oat. The development of new cultivars with improved beta-glucan concentration would be simplified if the mode of inheritance is understood. Three experiments, each using two paternal lines and their F1, F2, F3, BC1F2 and BC2F2 generations, were carried out to determine the inheritance of beta-glucan concentration. The results indicated that beta-glucan concentration was controlled by a minimum of 2 or 3 factor pairs with a predominantly additive type of gene action. In the majority of the generations, beta-glucan concentration was found to be positively correlated with protein content and negatively correlated with oil content. It was not correlated with grain yield, number of panicles/plant, or number of kernels per panicle. The broad-sense heritability of beta-glucan concentration ranged from 0.45 to 0.58 in the F3 generations, suggesting that it may be relatively easy to develop new oat cultivars with high- or low-beta-glucan concentration.
Key words: Avena sativa, oat, beta-glucan concentration, inheritance
Agriculture & Agri-Food Canada, Research Centre, P.O. Box 1000 A, Brandon, Manitoba, Canada R7A 5Y3
A three year study was conducted to assess the effect of tillage management on relative yield performance of selected cultivars of barley.The experiment was located on two differing textures of orthic black Chernozemic soils over three years. Relative yields differed significantly between cultivars within tillage systems, and between tillage systems, sites and years.All interactions were also highly significant.This suggests that barley variety performance trials should be conducted under the same tillage management system across sites and years and that significant interactions should be identified and mitigated, wherever possible. Failure to do so could lead to misidentification of high yield-performance cultivars and subsequent loss of economic opportunities to producers.
Key words: Barley, tillage, interactions, yield response
Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth, Dyfed SY23 3EB, UK
Pasture research in the UK has increasingly been aimed at understanding the mechanisms which underlie pasture plant responses to different managements. The need to develop agricultural systems which are both sustainable and economically viable has strengthened interest in reliable animal production from pasture and has emphasized the need to understand how white clover can best be maintained in the grazed sward. Breeders are focusing on meeting the nutritional requirements of the grazing animal and are enjoying increasing success in incorporating new genetic material from plant collections into varieties of grass and clover which are better able to withstand environmental stresses. Economic and environmental considerations have stimulated interest in gaining further insights into the nature of (and the reasons for) the species changes which follow reductions in fertilizer inputs and stocking rates. The possibility of harnessing the preferences of different grazing animals to influence vegetational change is being explored. Soil microbiology and nutrient availability in soils (and their influence on future productive capacity) are also influenced by reduced inputs and are subjects attracting increased interest. This paper discusses current understanding of these topics in the UK and identifies some specific problems which require further study.
Key words: clover, grass, grazing, pasture composition, plant breeding
1Semiarid Prairie Agricultural Research Centre, Agriculture and Agri-Food Canada, P.O. Box 1030, Swift Current, Saskatchewan, Canada S9H 3X2; 2525 2nd Ave NE, Swift Current, Saskatchewan, Canada S9H 2E5
Previous research in the semiarid prairie at Swift Current, Saskatchewan, indicated that optimum row spacing for forage production was 60 or 90 cm for crested wheatgrass (Agropyron cristatum (L.) Gaertner) and Russian wildrye grass (Psathyrostachys juncea (Fisch.) Nevski). However, recent research suggested that harvest method affects forage yield estimates from row spacing experiments. An experiment with three row spacings of mixtures of alfalfa (Medicago sativa L.) with crested wheatgrass and Russian wildrye grass was harvested mechanically and by hand.Yield differences between methods of harvesting were affected by row spacing; larger differences were observed at 15 cm than at 60 cm spacing, particularly for Russian wildrye grass. The highest hand-harvested forage yield estimates were observed in the narrowest row spacing. In a second experiment, plant density was evaluated for the same grasses using square grid spacings of 30, 45, 60, 75 and 90 cm apart. Decreasing plant density was associated with decreased hand-harvested forage yield in both species. In a third experiment, 60 and 90 cm row spacing resulted in more seed heads and lower leaf content than 30 cm row spacing. Leaf digestibility increased slightly with increased row spacing. These results suggest that 30 cm row spacing should be recommended to producers for sustainable pastures in the semiarid prairie region.
Key words: Forage yield, forage quality, leaf:stem ratio, plot technique
1AgResearch Grasslands, Private Bag 11008, Palmerston North, New Zealand; 2Agriculture and Agri-Food Canada, P.O. Box 1210, Charlottetown, Prince Edward Island, Canada
A series of experiments on white clover (Trifolium repens) was conducted to (1) field test white clover frost tolerant selections in a region subjected to freezing stress, and (2) evaluate and characterize, both in the field and in an artificial frosting environment, a number of white clover ecotypes from eastern Canada.
Within the lines produced from genotypes selected for frost tolerance, there was considerable variation in the field for tolerance to winter freezing based on both vigour and winter survival. However, some of the selections were very tolerant of the conditions with more than 90% survival after two Canadian winters. The ecotypes collected from eastern Canada were essentially acyanogenic with a small to medium leaf size. Their winter survival in the field was also variable ranging from 0 to 95% in one trial and 0 to 85% in another. However, survival of ecotypes was correlated between two field trials (r=+0.45, P<0.05). Artificial frosting damage was correlated with second year spring vigour (r=0.69, P<0.001), but not consistently with winter survival.
Ecotypes collected from cold regions were variable for both field and artificial frosting tolerance, but included germplasm that could be used in breeding programs seeking improved frost tolerance. Selection in artificial frosting environments can produce germplasm that is tolerant of winter freezing stress in the field.
Key words: White clover, frost tolerance,
winter hardiness, Trifolium repens, selection, ecotypes
1Research Centre, Agriculture and
Agri-Food Canada, P.O. Box 3000, Lethbridge, Alberta,
Canada T1J 4B1; 2Department
of Agricultural Food and Nutrition Science, University of Alberta, Edmonton,
Alberta, Canada T6G 2P5
Rough fescue grasslands are readily damaged by heavy grazing pressure in the summer but tolerate grazing in winter. The grasslands have physical and nutritive properties that make them suitable for winter grazing by cattle thereby reducing the cost of winter feeding while preserving the integrity of the grasslands. However, their forage value declines during winter through the degradation of biomass yield and quality. This study took place at the Agriculture and Agri-Food Canada, Range Research Substation located on the Porcupine Hills in southwest Alberta. The objectives of this study were to determine the dynamics of litter biomass for important forage species over winter, to examine the role of leaf position in the plant on biomass loss from leaves, and to determine the associated changes in crude protein, phosphorus, and acid detergent fibre of the leaves, and carbon and nitrogen. Leaves of Parry oat grass (Danthonia parryi Scribn.), Idaho fescue (F. idahoensis Elmer), and rough fescue (F. campestris Rydb.) were sampled at monthly intervals from August to March over 3 years to determine weight and chemical composition. Decomposition of these species, together with smooth aster (Aster laevis L.), was also tested for decomposition in the litter mass using nylon bags. Degradation of standing litter was most rapid in late summer and tended to decline toward stability by December. Biomass losses in leaves from August to March were similar (P < 0.05) among grass species. Over-winter losses in the litter mass tended to be greatest for smooth aster. Changes in the mineral and fibre concentrations of the herbage were typical of the trends expected for the period, that included late senescence and weathering, and followed closely the losses of biomass for the period. Forage decomposition is an important ecological process in mineral cycling and affects the quantity and quality of forage available for delayed grazing.
Key words: Standing litter, buried litter, biomass, forage quality, winter, Parry oat grass, Idaho fescue, rough fescue, smooth aster
1Research Centre, Agriculture and Agri-Food Canada, P. O. Box 3000, Lethbridge, Alberta, Canada T1J 4B1; 2Department of Crop Science and 3Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1
Physical properties of forages may provide a simple method of predicting animal voluntary feed intake. Physical measurements, such as shearing force, may indicate the resistance of the forage to particle breakdown during mastication. The objective of this study was to determine the effects of seeding rate on the physical characteristics and cell wall chemical constituents of alfalfa (Medicago sativa L.) stems, and to relate these characteristics to shearing strength. Stems of eight alfalfa cultivars (120, Legend, Multiking 1, OAC Minto, Saranac, Vernal, Vertus, WL320) seeded at 6, 12 and 24 kg ha--1 were harvested in the first and second production years and divided into three 16-cm segments: top, middle and bottom, and the force required to shear each segment was measured using a modified Ottawa Texture Measuring System. For both years, shearing force, segment weight and stem diameter measurements generally decreased as seeding rate increased when measured at the middle and bottom shearing segments on the stem, but this was not observed for the top shearing segment. Effect of seeding rate on differences in segment weight and stem diameter among cultivars was variable among years and stem segments. Concentrations of cell wall constituents in stems were not influenced by seeding rate, and these influenced shearing force to a lesser extent than physical characteristics. Shearing force was directly related to the diameter and weight of the stem. Because of the associations between shearing force and diameter and weight, physical characteristics of the stem may influence forage breakdown during mastication independently, and to a greater extent than cell wall chemical constituents.
Key words: Alfalfa, seeding rate, shearing force, cell wall chemical constituents, diameter, weight
1Research Centre, Agriculture and Agri-Food Canada, Pacific Agri-Food Research Centre, Summerland, British Columbia, V0H 1Z0 and 2Range Research Unit, Agriculture and Agri-Food Canada, 3015 Ord Rd., Kamloops, British Columbia, Canada, V2B 8A9
Freeze thaw scarification has been observed to increase the germination rate of alfalfa (Medicago sativa L.) seed containing a large proportion of hard (water impermeable) seed in a 7- d laboratory germination test; however a comparable increase in plant density is not always seen in the field. To investigate this discrepancy, a field experiment with untreated and scarified seed was carried out using cultivars with high (Apica: 35%, Barrier: 32%) and low (Apollo II: 1%, WL316: 0.3%) percentages of hard seed. Plants were counted at the 3-trifoliate leaf and 10% bloom stages in 1992, the planting year, and at 10% bloom in 1993. In the field, effects of scarification were seen only at the 10% bloom stage in 1992, increasing the plant densities of high hard seed cultivars by 17% while decreasing those of low hard seed cultivars by 10%. Two laboratory experiments were also done to determine the effect of temperature, lighting (light, shade, dark) and media (on blotter, in soil) on the germination of hard seed. Germination was highest at alternating 35/5°C and higher at 28/14°C than at constant 20°C. At 20/-10°C most germinated seed died. Differences among germination media and lighting treatments were small. Scarification may possibly have some negative effect on the quick germinating fraction of the seed in the field but the net effect for cultivars with a high hard seed content appears positive. Some seed identified as hard in a 7-d test at constant 20°C likely germinate and contribute to an alfalfa stand in the field when soil temperatures are higher. Thus the discrepancy previously observed between the laboratory and field results may possibly be accounted for in part by a negative effect of scarification and also by differences in temperature.
Key words: Medicago, germination, seed coat, temperature
Research Centre, Agriculture and Agri-Food Canada, Brandon, Manitoba R7A 5Y3
There is a lack of information on the interaction of harvest management, grass species and N-fertilizer interaction on forage quality and nitrogen use efficiency of dryland grasses. In a three year field trial, harvest management (2 cut, hay management vs. a 3-4 cut simulated pasture management system) and nitrogen fertilizer (0, 40, 80, 120, 160 kg N ha--1) were examined for their effects on protein yield (PY), protein content (PC), nitrogen use efficiency (NUE), nitrogen recovery (NR) and soil test nitrate-nitrogen (STN) under crested wheatgrass (Agropyron cristatum (L.) Gaertn.; CWG), meadow bromegrass (Bromus biebersteinii Roem & Schult.; MBR) and smooth bromegrass (Bromus inermis L.; SBR) swards. Generally, grasses managed under a two-cut hay system had lower (P<0.05) PC than grasses managed under a 3-4 cut simulated pasture system (and occasionally higher NR and NUE) but harvest management did not consistently affect PY. There were few consistent differences between grass species for PY, PC, NUE and NR with relative ranking and significance changing between site-years. Generally, MBR responded to N-fertilizer in a similar manner to previously studied dryland grasses such as CWG or SBR. N-fertilization increased PY and PC but did not consistently affect NUE, NR and STN.
Key words: Protein yield, protein content, nitrogen recovery, nitrogen use efficiency, hay, pasture
Department of Plant Science, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2
Castor summer rape (Brassica napus L.) is a high-erucic acid rapeseed cultivar with canola-quality meal. Castor has an average 4% yield advantange over Mercury rapeseed and is 4 g kg--1 higher in seed oil than Mercury. Castor is adapted to the southern B. napus growing regions of western Canada.
Key words: Rape (summer), high-erucic acid-low glucosinolate, cultivar description
Agriculture and Agri-Food Canada, Semiarid Prairie Agricultural Research Centre, Swift Current, Saskatchewan, Canada S9H 3X2
AC Crystal is a red-seeded spring wheat (Triticum aestivum L.). In combining high grain yield and resistance to prevalent races of common bunt in a semidwarf, photoperiod insensitive background it is similar to AC Taber. It has improvements relative to AC Taber: resistance to prevalent races of loose smut, except race T9, and stronger gluten properties. AC Crystal has improved resistance to leaf spots compared to Neepawa, AC Karma, and AC Foremost. It is eligible for grades of the Canada Prairie Spring (red) wheat class.
Key words: triticum aestivum L., cultivar description, loose smut resistance, common bunt resistance, high yield, red spring wheat
Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, Ottawa Ontario, Canada K1A 0C6
Medallion is a 2500 Crop Heat Unit soybean [Glycine max (L.) Merr.] cultivar with good yield potential.
Key words: Soybean, cultivar description
Eastern Cereal and Oilseed Research Centre,
Agriculture and Agri-Food Canada
Ottawa, Ontario, Canada K1A 0C6
AC Colombe is a 2300 Crop Heat Unit soybean [Glycine max (L.) Merr.] cultivar developed for natto soyfood production.
Key words: Soybean, cultivar description,
natto
Department of Horticulture, Michigan State University, East Lansing, MI, USA 48824
Levels of allozymic diversity were examined in native Michigan populations of diploid, Vaccinium myrtilloides, and the tetraploids, V. angustifolium and V. corymbosum. Plants from three populations of each species were included in the analysis. Levels of heterozygosity and the number of alleles were averaged over seven polymorphic isozyme loci within both populations and species. As has been found in other studies that compared closely related diploid and tetraploid species, the level of heterozygosity and number of alleles per locus were noticeably lower in the diploid V. myrtilloides (21.7%; 2.9) than in the tetraploids, V. angustifolium (57.1%; 3.4) and V. corymbosum (75.6%; 3.6). The average level of heterozygosity was almost 20% higher in V. corymbosum than V. angustifolium. These two tetraploid species may face distinct selective pressures or have differences in outcrossing rates.
Key words: Vaccinium myrtilloides, Vaccinium corymbosum, Vaccinium angustifolium, autotetraploidy
Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, Summerland, B.C., Canada V0H 1Z0
The dwarfing apple rootstock Ottawa 3 (O.3) produces trees slightly too large for high density plantings on fertile soils, but it is more cold hardy and better anchored than Malling 9. Our objective was to reduce the vigour of trees on O.3 by budding scions higher or planting the trees more shallowly. 'Summerland McIntosh' was budded at 15 cm onto O.3 and planted such that 6 to 14 cm of the rootstock shank was aboveground. Planting depth did not affect tree size, yield or yield efficiency. Increasing budding height from 5 to 25 cm increased vigour control, yield efficiency and the production of root suckers on O.3. Higher budding may be an effective way to reduce the vigour of trees on O.3 in areas where the greater root suckering is not a fireblight hazard.
Key words: Malus domestica Borkh., dwarfing rootstock
1Departamento de Agronomia, Universidade
Brasilia, C.P. 04477 Brasilia D.F. 70919.
2Departamento de Fitotecnia, Universidade
Federal de Viçosa, Viçosa MG 36571-000
3Laboratório de Genética
de Plantas CENARGEN-EMBRAPA - C.P. 02372 Brasília D.F. 70879-970;
In cassava, apomixis could fix hetereozygosity and prevent the transmission of systemic pathogens which complicate vegetative propagation of the crop. Evidence from maternal inheritance of RAPD markers and the structure of the embryonic sac in large progeny sets of two distinct genotypes have further confirmed that apomixis occurs in cassava. Here, we have built on an earlier report of apomixis in cassava in four ways (1) we estimated the rate of facultative apomixis in the range of 2% (2) we detected the occurence of apomixis in a second genotype, derived form a different interspecific cross;(3) apomictic behavior was demonstrated in an F1 individual and (4) embroynic evidence showed that the mode of apomixis is aposporic. Since apomixis was detected in an F1 interespecific hybrid suggests that genes for apomixis could be transferred directly to cultivated cassava from a wild relative.
Key words:
Department of Horticultural Science, North Carolina State University, Raleigh, NC 27695-7609
Optimum planting density and harvest stage were determined for once-over harvest of little-leaf and normal-leaf cucumbers. Three harvest stages (10%, 25%, and 50% oversize fruit) and four plant densities (37,000, 75,000, 150,000, and 300,000 plants/ha) were evaluated on little-leaf cucumber ('H-19') and normal-leaf cucumber ('Sumter' and 'Regal'). Plant density did not affect skin color, seedcell size, and seed size in the cultivars evaluated. However, lighter skin color, larger seedcell, and larger seed size were detected at the later harvest stages in 'H-19'. Harvest stage did not influence fruit skin color in 'Regal' and 'Sumter', but seedcell size and seed size increased quadratically with harvest stage. 'H-19' produced the highest yield (tonne/ha) and dollar value ($/ha) followed by 'Regal' and 'Sumter'. Considering fruit quality and dollar value, the 10% harvest stage at 330,000 plants/ha was the optimum stage and density for once-over harvest of 'H-19' under North Carolina growing conditions. Higher yield occurred at the later harvest stages, but poorer fruit quality (increased seed and seedcell size, and a lighter skin color) was associated with those stages. Fruit quality and dollar value of 'Regal' was best at the 10% harvest stage at approximately 240,000 plants/ha, while 200,000 plants/ha was best for 'Sumter'.
Key words: Cucumis sativus, plant type, spacing, crop ideotype, vegetable production
1University of Guelph, Horticultural Research Institute of Ontario, Horticultural Experiment Station, Simcoe, Ontario, Canada N3Y 4N5; 2Agriculture and Agri-Food Canada, Vineland Station, Ontario, Canada L0R 2E0.
A six-year (1987-1992) experiment continuous on the same site evaluated potential problems for yield, nematodes and diseases with tomatoes (Lycopersicon esculentum Mill.) grown in a strip-till system. Treatments consisted of conventional tillage (CT) and strip tillage (ST), rye (Secale cereale L.), wheat (Triticum aestivum L.) and perennial ryegrass (Lolium perenne L.) cover crops and a two year rye-tomato rotation. Results of the first 5 years indicated a decrease in tomato yield over time for both tillage treatments and cover crops. However, yield rebounded overall for treatments in 1992 with highest yield in the rye-tomato rotation. We suspect this was a result of high populations of root-knot nematodes which collapsed over the winter of 1991/1992. Tomato yields were lower following wheat and perennial ryegrass than rye. In only one year out of six, strip-tillage reduced yield compared to conventional tillage. Bacterial speck/spot symptoms on foliage, although minor, were significantly greater in ST than in CT plots during the last 3 years. No major trends in incidence and severity of bacterial and fungal diseases and of disorders of fruit were evident during the 5 year period and neither fruit yield nor quality were significantly affected by these factors. Root-knot nematodes (Meloidogyne hapla Chitwood) were numerically less in the rye-tomato rotation than in other treatments; both root-knot and root lesion nematodes (Pratylenchus penetrans (Cobb)) tended to be less numerous under CT than under ST. Strip-tillage is feasible for machine harvest processing tomatoes. However, we are concerned about the tendency of tomatoes grown under reduced tillage to have lower yields compared to conventional tillage. More work is required on the interactions of cultivars, cover crops and nematodes in soil conservation systems.
Key words: Lycopersicon esculentum, bacterial speck/spot, foliar diseases, root-knot nematodes, Meloidogyne hapla, root lesion nematodes, Pratylenchus penetrans, tillage, yield.
1USDA, ARS, SP Range Research Station, 2000 18th Street, Woodward, OK 73801, USA; 2Department of Crop Science and Plant Ecology, 3Department of Horticulture Science, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK, CANADA S7N 5A8
Resistance to leaf rust (Puccinia recondita f. sp. tritici Rob. ex Desm.) is common in Triticum monococcum L. For example, the 49 accessions in the University of Saskatchewan collection all gave a fleck reaction to leaf rust race CBB. To obtain some indication of whether they all carried the same gene, a set of diallel crosses was made among five of the accessions and three extra crosses were made between two additional accessions and two in the diallel set. The 13 F2 populations involving a total of seven accessions were tested with LR CBB and no segregation for susceptible seedlings occurred.Thus, the seven T. monococcum accessions all carried at least one gene in common.To determine the number of genes involved in leaf rust resistance, four crosses were made between a highly resistant accession, TM157 (IT 0;), and four moderately resistant ones (IT 2-).The F2 populations segregated for two independent dominant genes, one conditioning a fleck reaction and one a type 2 reaction. All seven highly resistant accessions must carry the first gene. Two of the T. monococcum accessions were resistant to stem rust (P. graminis f. sp. tritici Eriks. & Henn.) SR TMH. They proved to carry single genes for resistance, Sr22 in TM65 and Sr35 in TM157.
Key words: Wheat, leaf rust, stem rust, inheritance
Agriculture and Agri-Food Canada, Greenhouse and Processing Crops Research Centre, Harrow, Ontario, N0R1G0; Research Centre, 440 University Avenue, P.O. Box 1210, Charlottetown, Prince Edward Island, C1A7M8
The yield response of spring barley (Hordeum vulgare L. Cv "Morrison") to a range of densities of wild radish (Raphanus raphanistrum L.), wild oat (Avena fatua L.), hemp-nettle (Galeopsis tetrahit L.), and corn spurry (Spergula arvensis L.) was investigated in field experiments on Prince Edward Island from 1991 through 1994. Barley yield was modelled as a function of both barley and weed density. In the absence of weed competition, barley seed yield, number of main shoots, number of heads, and thousand kernel weight varied significantly over the four years of the study. Increasing densities of wild radish and wild oat reduced the number of barley heads primarily by interfering with tillering, but wild oat also reduced barley thousand kernel weight. Hemp-nettle and corn-spurry at densities up to 200 plants m-2 had little effect on barley yield, except in a year of low barley yield potential. Estimated economic thresholds for wild radish, wild oat, hemp-nettle and corn spurry at a barley population of 250 plants m--2, were 37, 45, 122 and 297 plants m--2, respectively, assuming a weed-free yield of 4 t ha--1, a crop price of $100 t--1, and weed control costs of $30 ha--1.
Key Words: Avena fatua, Galeopsis tetrahit, Hordeum vulgare, Raphanus raphanistrum, Spergula arvensis, yield loss, weed interference, economic threshold
Crop Science Dept., Univ. of Guelph, Guelph, Ontario, Canada N1G 2W1
White bean producers often perceive that increased herbicide inputs are required with the adoption of conservation tillage. Acceptance of conservation tillage systems for this crop would increase if effective weed management practices were assured. In 1991 and 1992, various weed management strategies were evaluated in white bean (Phaseolus vulgaris L.) grown with three tillage systems at two sites in southern Ontario. Experiments were newly-established each year following corn harvested for grain. Primary tillage treatments were fall moldboard plowing, fall chisel plowing, and first year no-till. Combinations of mechanical weeding, metobromuron [3-(4-bromophenyl)-1-methoxy-1-methylurea] herbicide broadcasted at two rates, and a band application of the herbicide were investigated in each tillage system. Timely rotary hoeing reduced weed numbers in moldboard plow and chisel plow treatments, but was not effective in no-till. Weeds were adequately controlled in all tillage systems with mechanical treatments following a herbicide either broadcasted at a reduced rate or banded over the crop row. Metobromuron broadcasted at the full recommended rate alone controlled weeds in no-till; in contrast, the degree of weed control was poor without mechanical cultivation in both moldboard and chisel plow systems. Integrating mechanical and chemical control methods was more beneficial in tilled systems. Overall weed populations were lower in first-year no-till than moldboard plow or chisel plow tillage systems. White bean producers who adopt conservation tillage under conditions similar to those investigated can be assured of effective weed management alternatives as well as bean yields equivalent to conventional tillage.
Key Words: Conservation tillage, weed management, rotary hoe, inter-row cultivation, Phaseolus vulgaris