Lamb, E. G., Shirtliffe, S. J. and May, W. E. 2011. Structural equation modeling in the plant sciences: An example using yield components in oat. Can. J. Plant Sci. 91: 603-619. Structural equation modeling (SEM) is a powerful statistical approach for the analysis of complex intercorrelated data with a wide range of potential applications in the plant sciences. In this paper we introduce plant scientists to the principles and practice of SEM using as an example an agronomic field trial. We briefly review the history of SEM and path analysis and introduce the statistical concepts underlying SEM. We demonstrate the use of observed and latent variable structural equation models using a multi-site multi-year field trial examining the effects of seed size and seeding density on the plant density and yield of oat in Saskatchewan. Using SEM allowed for insights that a standard univariate analysis would not have revealed. We show that seeding density has strong effects on plant and panicle density, but has very limited effects on final yield. Plant density has a consistent non-linear effect on panicle density across location that was not affected by precipitation. In contrast, the implicit effect of precipitation on seed number appears to be the main driver for final yield. Incorporating precipitation data into the model demonstrates how mechanistic models can be developed by including in the path diagram variables that would normally treated as random factors in a mixed model analysis. Finally, we provide a guideline to assist plant scientists in determining whether SEM is an appropriate method to be used for the analysis of their data.

Yang, R.-C. and Juskiw, P. 2011. Analysis of covariance in agronomy and crop research. Can. J. Plant Sci. 91: 621-641. Analysis of covariance (ANCOVA) is a statistical technique that combines the methods of the analysis of variance (ANOVA) and regression analysis. However, ANCOVA is an advanced topic that often appears towards the end of many textbooks, and thus, it is either taught cursorily or ignored completely in many statistics classes. Additionally, many elaborated applications of ANCOVA to agronomy and crop research along with uses of the latest statistical software are rarely described in textbooks or classes. The objectives of this paper are to provide an overview on conventional ANCOVA and to introduce more advanced uses of ANCOVA under mixed models. We describe three elaborate applications including (i) the use of ANCOVA for dissecting dosage responses for different treatments, (ii) stability of treatments across multiple environments and (iii) removal of spatial variation that is not effectively controlled by blocking. These analyses illustrate that ANCOVA is either a simpler analysis or provides more information than conventional statistical methods. We provide a technical appendix (Appendix A) on principles and theory underlying mixed-model analysis of ANCOVA along with SAS programs (Appendix B) for more uses and in-depth understanding of this powerful technique in agronomy and crop research.

Yan, W., Pageau, D., Frégeau-Reid, J., Lajeunesse, J., Goulet, J., Durand, J. and Marois, D. 2011. Oat mega-environments and test-locations in Quebec. Can. J. Plant Sci. 91: 643-649. The Quebec agricultural regions have traditionally been divided into three zones. Zone 1 includes the small, southern most regions in the Montreal plain, zone 3 includes the large, discontinuous northern regions spreading from the west to the east of the province, and zone 2 includes areas between zone 1 and zone 3. Genotypic main effect (G) plus genotype-by-environment interaction (GGE) biplot analysis of the yield data from the Quebec Oat Registration and Recommendation trials during 2006-2009 revealed that the Quebec oat-growing regions can be divided into two distinct mega-environments: the small zone 1 region and the much larger zone 2 plus zone 3 regions. Due to the large genotype by mega-environment interactions, cultivar evaluation and recommendation must be conducted specifically to each mega-environment. However, a zone 3 test location, La Pocatière, consistently behaved like a zone 1 location in terms of cultivar ranking. Therefore, La Pocatière cannot be used to represent the zone 3 region, and cultivar recommendation for the regions represented by this location should be based on data from this location plus the zone 1 locations. In addition, climatic and soil data were examined in an attempt to explain this observation. The methodology adopted in this work may be of value to similar studies for other crops and in other regions.

Reid, L. M., Xiang, K., Zhu, X., Baum, B. R. and Molnar, S. J. 2011. Genetic diversity analysis of 119 Canadian maize inbred lines based on pedigree and simple sequence repeat markers. Can. J. Plant Sci. 91: 651-661. Since the early 1920s Agriculture and Agri-Food Canada (AAFC) has been developing maize varieties and inbred lines adapted to the early maize growing regions. These inbreds represent a large group of genetically diverse genotypes; however, many of the inbreds are of unknown heterotic backgrounds. The purpose of this study was to classify 119 elite maize inbred lines released from AAFC into heterotic groups using both pedigree data and simple sequence repeat (SSR) markers and also to explore the consistency among different classification analyses. Pedigree analysis placed the inbred lines into eight groups, six of which corresponded to known major heterotic groups representing Iowa Stiff Stalk Synthetic (BSSS), European flint, Lancaster, Minnesota 13, Early Butler, and Iodent; the two remaining groups consisted of germplasm derived mostly from Pioneer 3990 or Pioneer 3994 sources. Simple sequence repeat analysis of 105 loci resulted in a clustering of the inbreds into 10 groups. In comparison with the grouping based on pedigree, the SSR clustering groups had some discrepancies and groups of genetically similar germplasm, based on pedigree, could not always be confirmed with molecular markers. The results of this study will allow researchers and maize breeders to make more informed decisions on the use of these inbreds in breeding programs.

Kirk, A. P., Entz, M. H., Fox, S. L. and Tenuta, M. 2011. Mycorrhizal colonization, P uptake and yield of older and modern wheats under organic management. Can. J. Plant Sci. 91: 663-667. Arbuscular mycorrhizal fungi (AMF) are important for plant nutrient uptake, and mycorrhizal dependence varies between wheat genotypes. Cultivar selection under fertilized conditions may have reduced mycorrhizal associations in modern cultivars. This study investigated AMF colonization, tissue P and grain yield of five modern (post 1990) and five older (pre 1970) spring wheat cultivars over 4 site-years in Manitoba. Older cultivars actually had significantly lower AMF colonization and grain yield than modern cultivars, but no tissue P concentration differences were observed. The two highest yielding lines were released after 2004, and one of these (FBC Dylan) was selected for suitability in organic farming systems.

Kosinski, S. M., King, J. R., Harker, K. N., Turkington, T. K. and Spaner, D. 2011. Barley and triticale underseeded with a kura clover living mulch: Effects on weed pressure, disease incidence, silage yield, and forage quality. Can. J. Plant Sci. 91: 677-687. Our objective was to evaluate the effects of seeding barley (Hordeum vulgare L.) and triticale (×Triticosecale wittmack) into a living mulch of kura clover (Trifolium ambiguum M. Bieb.) on weed pressure, barley leaf disease levels, silage yield, and forage quality. Field studies were conducted at two locations in the Parkland region of Alberta, Canada, in 2006 and 2007. Barley and triticale were seeded, at three different soil nitrogen levels, into an established living mulch of kura clover that was either unsuppressed or chemically suppressed with glyphosate at 0.41 kg a.i. ha^-1 prior to cereal seeding. Barley and triticale sole crops were also included for comparison. The presence of the suppressed and unsuppressed kura clover living mulches significantly decreased weed pressure in 2007 and barley leaf disease incidence in 2006 and 2007. Silage DM yield of the cereal sole crops ranged from 5.18 to 7.02 Mg ha^-1, compared with yields of 4.57 to 5.21 Mg ha^-1 from the unsuppressed living mulch treatments and from 3.95 to 6.00 Mg ha^-1 from the suppressed living mulch treatments. The kura clover increased the relative feed value of the silage. Based on these results, there is the potential for a suppressed kura clover living mulch to be utilized for cereal silage production in Alberta.

Berard, N. C., Wang, Y., Wittenberg, K. M., Krause, D. O., Coulman, B. E., McAllister, T. A. and Ominski, K. H. 2011. Condensed tannin concentrations found in vegetative and mature forage legumes grown in western Canada. Can. J. Plant Sci. 91: 669-675. There has been limited effort to examine condensed tannin (CT) concentrations of forage legume species grown in western Canada. Using the butanol-HCl technique, extractable CT concentrations were measured in Trifolium hybridum L., T. ambiguum M. Bieb, T. pratense L., T. repens L., Dalea purpurea Vent., Onobrychis viciifolia Scop., Lotus corniculatus L., Medicago sativa L., and Astragalus cicer L. collected from research and variety trial plots across the Canadian prairies. Above ground plant biomass was harvested at the vegetative and mature physiological stages for two growing seasons. Dalea purpurea, a native legume, had the highest mean CT concentration of 68.6±22.6 g kg^-1 DM, with minimum and maximum values ranging from 37.9 to 92.9 g kg^-1 DM. Onobrychis viciifolia had the second highest mean CT concentration (46.0 g kg^-1 DM) with a range of 16.3 to 94.4 g kg^-1 DM. The third highest mean CT concentration of 15.1 g kg^-1 DM was found in L. corniculatus with a range of 0.0 to 25.7 g kg^-1 DM. Forage biomass had higher CT concentrations (P<0.05) when harvested at the mature stage for all species except O. viciifolia, which had higher CT concentrations in the vegetative state. The potential benefit of inclusion of these species in ruminant diets at the observed concentrations requires further exploration.

Pantel, A., Romo, J. T. and Bai, Y. 2011. Above-ground net primary production of plains rough fescue [Festuca hallii(Vasey) Piper] after a single defoliation on five landform elements. Can. J. Plant Sci. 91: 689-696. Above-ground net primary production (ANPP) was determined for plains rough fescue [Festucahallii (Vasey) Piper] following a single defoliation to 7.5 cm stubble height on five landform elements in the Northern Mixed Prairie. The landform elements included north aspect-concave slopes, north aspect-convex slopes, south aspect-concave slopes, south aspect-convex slopes, and level uplands. Above-ground net primary production was determined for 2 yr after defoliating plants in May through November. Above-ground net primary production after defoliation was not dependent on landform elements in the first (P=0.23) and second years (P=0.22) after defoliation. In the first year after June through September defoliation, ANPP was reduced 29 to 41% (P <0.01), whereas May, October, or November defoliation had no significant effect on ANPP. Above-ground net primary production did not vary significantly (P=0.61) among months of defoliation in the second year after defoliation. Less ANPP in the first year after June through September defoliation indicates the need for ≥1 yr of deferred use to allow plants to regain their production potential. Unaffected ANPP after May, October, or November defoliation suggests plains rough fescue can be grazed annually. Recuperation of ANPP after defoliation depends on the month of the year in which plains rough fescue is defoliated, but not on landform elements in the Northern Mixed Prairie.

Chen, H., Seguin, P., Jabaji, S. and Liu, W. 2011. Spatial distribution of isoflavones and isoflavone-related gene expression in high and low isoflavone soybean cultivars. Can. J. Plant Sci. 91: 697-705. Soybean contains high concentrations of isoflavones that have putative health-beneficial effects. A study was conducted to document the spatial distribution of isoflavones and the expression of 14 key genes and gene homologs encoding enzymes involved in isoflavone synthesis using quantitative reverse transcription (QRT)-PCR. Genes studied included phenylalanine ammonia lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), chalcone reductase (CHR), and isoflavone synthase (IFS). Two cultivars were used, AC Proteina and AC Orford, high- and low-isoflavone cultivars, respectively. Plants were harvested at the seed filling stage (R5) and were separated into leaf, stem, root, flower, pod, and seed parts. The present study revealed that at the R5 stage the expression of 14 key genes and gene homologs involved in isoflavone synthesis is observed in all plant parts, being, however, minimal in pods and seeds and greatest in leaves and roots. Gene expression data parallel isoflavone concentrations, which are also minimal in pods and seeds. In most cases, expression of all homologs of a given gene family was comparable in specific parts, the expression of homologs not being part-specific. Finally, gene expression differences between cultivars also paralleled differences observed in their isoflavone concentrations.

Li, Q., Tong, H., Zhang, Z., Zhao, Z. and Song, X. 2011. Inheritance and development of EST-SSR marker associated with turnip mosaic virus resistance in Chinese cabbage. Can. J. Plant Sci. 91: 707-715. Turnip mosaic virus (TuMV) is one of the major pathogens infecting Brassica crops (including Chinese cabbage), and often causes serious reductions in yield and quality. Breeding for resistant cultivars is complicated by the existence of numerous TuMV strains and isolates. The objective of this research was to determine the mode of inheritance and to develop molecular markers associated with TuMV resistance in Chinese cabbage. F₁ and F₂ populations were developed from the cross between 71-36-2 (susceptible) and 73 (resistant) lines and mechanically inoculated with TuMV-C4. Inheritance analysis by visual scoring and enzyme-linked immunosorbent assay (ELISA) indicated that resistance to TuMV-C4 in this cross was controlled by one recessive gene. A total of 132 EST-SSR primers were designed from EST sequences available in public databases. Seven primers detected polymorphism between parental genotypes. Marker HCC259 was associated with the TuMV resistance Ph-retr02. The distance between the marker and the TuMV resistance gene retr02 was 3.8 cM. This is the first co-dominant marker linked to the TuMV resistance gene with a distance less than 5.0 cM in Chinese cabbage. This marker was suitable for TuMV-C4 resistance screening in progenies from the cross between lines 73 (resistant) and susceptible line, 71-36-2. The usefulness of this marker was validated in 21 additional resistant and susceptible lines. This marker has the potential to simplify and accelerate breeding Chinese cabbage cultivars resistant to TuMV-C4.

Clasen, B. M., Moss, N. G., Chandler, M. A. and Smith, A. G. 2011. A preliminary genetic structure study of the non-native weed, common tansy (Tanacetum vulgare). Can. J. Plant Sci. 91: 717-723. Common tansy is an herbaceous perennial member of the Asteraceae and is considered a weed in North America. Common tansy was introduced deliberately for use as a funerary herb, medicine, preservative, and animal and insect repellent. It is known to escape cultivation and invade disturbed areas, spreading both sexually and asexually. This paper reports a preliminary analysis of the genetic structure of 10 invasive common tansy populations in Minnesota and Montana, USA, and Alberta, Canada. Ninety polymorphic loci were found using six inter simple sequence repeat (ISSR) primers used to amplify DNA from 40 individuals from 10 discrete populations. The diversity within and among populations was assessed using the Dice coefficient of similarity and AMOVA. The AMOVA showed that diversity within populations was generally high and that there was relatively small variation among populations. An unweighted pair-group with arithmetic mean (UPGMA) dendrogram was constructed based on the distance between populations, and demonstrated substantial and distinct clustering of a population from Ramsey County, Minnesota. A principal coordinates analysis clustered all individuals from Ramsey County distinctly from other individuals, indicating a possible limited gene flow among this population and the other populations sampled in this study. Understanding genetic diversity and the distribution of diversity within and among populations may help predict the potential for successful management of common tansy populations in North America.

Hébert, F. and Thiffault, N. 2011. The Biology of Canadian Weeds. 146.Rhododendron groenlandicum(Oeder) Kron and Judd. Can. J. Plant Sci. 91: 725-738. Rhododendron groenlandicum (Oeder) Kron and Judd, bog Labrador tea, is an evergreen shrub from the Ericacae family native to North America. Bog Labrador tea is associated with the later stages of forest successions in black spruce forest stands of the boreal ecosystems with cool climates, but responds aggressively to forest openings where it is already present. In general, bog Labrador tea is associated with nutrient-poor, acidic soils, with drainage ranging from moist to wet. Layering is the main regeneration strategy of the species; evidence suggests that this could be especially true following disturbances that open the forest canopy. Sexual reproduction maintains viability in undisturbed communities through wind or water dispersal. Rhododendron groenlandicum acclimates more rapidly relative to black spruce after perturbations through a higher rate of resource utilization when resources are available. The species is a highly competitive shrub for soil nutrients; it competes with regenerating conifers for soil nitrogen and phosphorus. It can also assimilate organic nitrogen from the soil through its mycorhizae. These characteristics may lead to the formation of ericaceous heaths that can stay unforested indefinitely. However, this species can be eradicated by herbicides (glyphosate) and heavy site scarification can limit its propagation.

Cavers, P. B., Qaderi, M. M., Threadgill, P. F. and Steel, M. G. 2011. The Biology of Canadian Weeds. 147.Onopordum acanthiumL. Can. J. Plant Sci. 91: 739-758. In Canada, Scotch thistle, Onopordum acanthium L. (Asteraceae) is primarily a weed of well-drained natural areas and ruderal habitats such as abandoned gravel pits. It is classed as a noxious weed in Ontario and the North Okanagan region of British Columbia but is common only in southern Ontario. Native to southern Europe and southwestern Asia, it has been introduced to almost 50 countries in all continents except Antarctica. In parts of the United States it is a strongly competitive species that infests small grain fields and competes with desirable forage species in rangelands. It does have desirable attributes and has many uses including being consumed as a vegetable, used as a source of honey, yielding a burnable oil, incorporated in medications for many human ailments, providing grazing for goats, sheep and cattle and being grown as a garden ornamental. Despite its limited range in Canada, several distinct biotypes, differing in morphology, phenology and important ecological attributes, such as dormancy and longevity of cypselas (fruits) in the soil, have been described from southern Ontario. In Australia, a fertile hybrid of O. acanthium and O. illyricum is a major weed and there are concerns that these two species could be progenitors of a similar hybrid in North America.

Cici, S. Z. H. and Van Acker, R. C. 2011. Relative freezing tolerance of facultative winter annual weeds. Can. J. Plant Sci. 91: 759-763. To understand why some of the facultative winter annual weeds are more abundant in spring rather than both in fall and spring, we assessed the freezing tolerance and re-growth capacity of 12 species collected across Canada. Our study allowed us to classify these species in three broad categories based on their relative tolerance to freezing temperatures. Freezing scores and biomass reproduction after freezing were generally consistent with field observations. It was shown that early emergence of weeds in spring is not, however, systematically related to superior freezing tolerance.

Privé, J-P., Russell, L. and LeBlanc, A. 2011. Impact of reflective groundcover on growth, flowering, yield and fruit quality in Gala apples in New Brunswick. Can. J. Plant Sci. 91: 765-772. A 5-yr field study was conducted in New Brunswick, Canada, to assess the impact of a reflective groundcover (Extenday^TM) on Gala (Malus×domestica Borkh.) apple trunk cross-sectional area (TCSA), flowering, yield and fruit quality. Overall, a 25% increase in the total number of fruit per tree was realized with use of the 3-m wide reflective groundcover on the orchard floor between tree rows from full-bloom until 3 wk post-harvest; this translated to 26% greater total yield per tree and 16% greater yield efficiency. No overall effects on fruit quality at harvest were associated with use of the reflective groundcover. Trees with reflective groundcover exhibited a greater yearly percentage increase in TCSA (18.5%) than those without (15.0%); neither flowering nor fruit set was affected in any year. These increases in productivity were mediated by the enhanced canopy light environment provided by the reflective groundcover. The primary economic benefit to be derived from use of the Extenday^TM reflective groundcover in apple production in the Maritime region is through the capacity to produce higher-yielding crops of fruit on larger trees (increased yield efficiency), without compromising fruit quality. This improvement in production efficiency could translate to an increase in 4.5 t ha^-1 of marketable fruit in New Brunswick.

Braun, L. C., Gillman, J. H., Hoover, E. E. and Russelle, M. P. 2011. Nitrogen fertilization for new plantings of hybrid hazelnuts in the Upper Midwest of the United States of America. Can. J. Plant Sci. 91: 773-782. Seed-propagated hybrids of Corylus avellana and C. americana are a potential crop for the Upper Midwest. Current N recommendations for hazelnuts are based on research on clonally propagated C. avellana in Oregon and may not be applicable in the Upper Midwest due to differing soils, climate, and plant genetics. We established three field plots in 2003 to test N fertilization rates on new plantings, with rates up to 33 g N plant^-1 as ammonium nitrate applied annually in the spring, starting 2 wk after transplanting. We observed a strong negative linear effect of N rate on plant survival. In the second year we added trials on same-aged plants that had not previously been fertilized and found no N effect on survival. We concluded that waiting 1 yr after transplanting before fertilizing increases plant survival, but even then N requirements during establishment years are very low for hybrid hazelnuts. Standard leaf N concentrations for C. avellana in Oregon are roughly applicable to hybrid hazelnuts, except that the threshold between deficiency and sufficiency should be raised slightly to 1.9% N. The current threshold between deficient and sufficient, 2.2%, should be regarded as a target, rather than as a threshold to be exceeded.

Cutforth, H., McConkey, B., Angadi, S. and Judiesch, D. 2011. Extra-tall stubble can increase crop yield in the semiarid Canadian prairie. Can. J. Plant Sci. 91: 783-785. Previous research in the semiarid prairie showed that crop yields increased as the height of standing stubble increased to 30 cm. Recent technology permits seeding into higher standing stubble. A 3-yr (2001-2003) study was conducted at Swift Current, SK, to determine how seeding canola, pulse, and wheat into cultivated, short (about 15 cm high), tall (about 30 cm high), and extra-tall (about 45 cm high) standing stubble affected crop yield. Crop yield and the overall average water use efficiency increased linearly as stubble height increased to 45 cm. Water use was independent of stubble height.

Mitchell Fetch, J. W., Brown, P. D., Ames, N., Chong, J., Fetch, Jr., T. G., Haber, S. M., Menzies, J. G., Tekauz, A., Townley-Smith, T. F. and Stadnyk, K. D. 2011. Summit oat. Can. J. Plant Sci. 91: 787-791. Summit is a white-hulled spring oat (Avena sativa L.) cultivar postulated to carry the crown rust resistance combination Pc38, Pc39, Pc48, and Pc68, which was effective against the prevalent pathotypes of crown rust on the Canadian prairies at the time of its release. It has very good resistance to loose and covered smut, moderately good resistance to most of the prairie stem rust races (likely due to the presence of Pg2 and Pg13) and is resistant to moderately resistant to barley yellow dwarf virus (BYDV). Summit has good kernel weight, percent plump kernels, and percent thin kernels. Summit exhibits high yielding capacity in the oat growing areas of western Canada. Summit was registered (Reg. No. 6529) in Canada 2008 November 29.

Bowley, S. R. and Hancock, D. 2011. DIVIDEND VL orchardgrass. Can. J. Plant Sci. 91: 793-795. DIVIDEND VL is a late-maturing orchardgrass (Dactylis glomerata L.) cultivar for silage and hay production in mixtures with alfalfa (Medicago sativa L.) in eastern Canada. The population was developed at the University of Guelph, Guelph, ON. DIVIDEND VL matured at a slower rate when grown in pure stand and in binary mixtures with alfalfa compared with the cultivars OKAY and Rapido. When harvested at the same date, DIVIDEND VL averaged 7% lower in biomass yield compared with OKAY, but the herbage was less advanced in its maturity.

DePauw, R. M., Knox, R. E., McCaig, T. N., Clarke, F. R. and Clarke, J. M. 2011. Muchmorehard red spring wheat. Can. J. Plant Sci. 91: 797-803. Based on 36 replicated trials over 3 yr, Muchmore, a doubled haploid hard red spring wheat (Triticum aestivum L.), averaged up to 20% more grain yield than the checks. It matured significantly later than AC Barrie, Katepwa and Lillian. Muchmore was significantly shorter than all of the checks and was significantly more resistant to lodging than Katepwa, Laura and Lillian. Muchmore had significantly higher test weight than Katepwa and Lillian, intermediate kernel weight relative to the checks, and meets the end-use quality specifications of the Canada Western Red Spring wheat market class. Muchmore expressed resistance to prevalent races of leaf rust, stem rust and common bunt, moderate resistance to loose smut, and moderate susceptibility to fusarium head blight.

Randhawa, H. S., Sadasivaiah, R. S., Graf, R. J. and Beres, B. L. 2011. Bhishaj soft white spring wheat Can. J. Plant Sci. 91: 805-810. Bhishaj is a soft white spring wheat (Triticum aestivum L.) that meets the end-use quality specifications of the Canada Western Soft White Spring class. Bhishaj is well-adapted to the wheat growing regions of southern Alberta and southern Saskatchewan. Based on data from the Western Soft White Spring Wheat Cooperative Registration Test from 1999 to 2001 and 2006 to 2009, Bhishaj exhibited high grain yield, mid-season maturity, semi-dwarf stature with moderate straw strength, and good resistance to shattering. Bhishaj expressed resistance to the prevalent races of leaf rust, stripe rust and powdery mildew, intermediate response to loose smut, susceptibility to stem rust, common bunt, and Fusarium head blight. Based on end-use quality analysis performed at the Grain Research Laboratory of the Canadian Grain Commission, Bhishaj had similar milling and baking performance as the check cultivars AC Reed and AC Phil.