Halberg, N. 2012. Assessment of the environmental sustainability of organic farming: Definitions, indicators and the major challenges. Can. J. Plant Sci. 92: 981-996. The debate over agricultural sustainability continues due to the challenges of reducing externalities of intensive farming methods and preserving vital natural capital, but many definitions of sustainability are too wide to allow for a prioritized assessment. This paper uses a more narrow definition of agricultural sustainability focusing on the functional integrity of a system to highlight specific aspects of vital importance for the long-term resilience and reproducibility of agricultural systems. Key areas of resource sufficiency are also identified. Based on a review of scientific literature the relative sustainability of organic agriculture is assessed with a focus on environmental impact and resource use in Europe and North America. While there are many examples of organic agriculture with improved performance in terms of soil fertility and preservation of biodiversity, in other aspects - such as resource use per kilogram product - the difference to conventional farming is less important. The paper presents a framework for selection of indicators based on the principles of organic agriculture which may be used to monitor and improve the performance of organic agriculture with respect to functional integrity and resource sufficiency. The differences between comparable organic farms may be used for improving farm practices through a benchmarking process.

Burlakoti, R. R., Lynch, D., Halde, C., Beach, T., Dahal, S. and Debnath, S. C. 2012. Organic agriculture project in Nepal: An international twinning partnership program initiative. Can. J. Plant Sci. 92: 997-1003. Agriculture is the major occupation in Nepal, contributing 32% of total gross domestic product (GDP) and 75% of the country's exports. The traditional way of farming using low inputs (inorganic fertilizers and pesticides) provides opportunities to adopt organic farming for diversified crops, with potential domestic markets and export markets in Japan and Europe. With a goal of improving the livelihood of rural ethnic marginalized farmers of the mid-western hill of Nepal, an international development project was started through a joint effort of the Agricultural Institute of Canada (AIC), Sustainable Agriculture Development Program (SADP) Nepal, the Canadian Society of Agronomy (CSA) and the Canadian Society for Horticultural Science (CSHS). The project, entitled “Research and support to organic agriculture in Tanahu district of Nepal”, commenced in April 2010. Canadian team members visited Nepal in December 2009 and 2010. To date, the project has successfully strengthened the organizational capacity of the lead organization (SADP, Nepal), conducted a baseline assessment study in the project area, assessed the potential domestic market for organic product, promoted organic farming among the ethnic marginal farmer groups (Kumal and Darai), and identified and established a strong collaborative project link with the agricultural university and scientific societies of Nepal. A proposed further 5-yr (2011 to 2016) project aims to change the traditional subsistent farming to commercial organic farming in the target area and aims to improve the livelihood of the farmers through better income generation from organic farming. The project will include scientific research on organic farming led by the Agriculture and Forestry University, Nepal, in collaboration with other scientific societies of Nepal. The CSA and CSHS will provide technical input, advice for the project, and monitor and supervise the project progress.

Knight, J. D. 2012. Frequency of field pea in rotations impacts biological nitrogen fixation. Can. J. Plant Sci. 92: 1005-1011. Economic, environmental and energy concerns about the use of nitrogen (N) fertilizers in crop production have prompted the examination of increasing the frequency of pulses in crop rotations to capitalize on biological nitrogen fixation (BNF). Plots from a field experiment established in 1998 at the Agriculture and Agri-Food Canada Research Farm at Scott, SK, were sampled in 2008, 2009 and 2010. Rotations that included pea every year (continuous pea), every second year (pea-wheat), every third year (pea-canola-wheat) and every fourth year (canola-wheat-pea-wheat) were evaluated for BNF using the enriched ¹⁵N isotope dilution technique. Nitrogen from BNF in the seed and straw, total above-ground N, seed and straw yield and soil available N and P were evaluated. In 2 of 3 yr, the highest BNF occurred in the two most diverse rotations. Continuous cropping of pea resulted in drastically low BNF in 2008 and 2009. Nitrogen derived from atmosphere in the continuous pea was 15% compared with an average of approximately 55% across all other rotations in these 2 yr. The reduction in BNF was not due to lower productivity in the continuous pea rotation, nor from higher initial soil inorganic N levels inhibiting BNF. In the third year of the study (2010), the more than double the normal precipitation received during the growing season stimulated BNF in pea in the continuous pea rotation. Determining whether the rotation effects on BNF are due to N mineralization of the previous years' crop residues requires further investigation.

Clements, D. R. and DiTommaso, A. 2012. Predicting weed invasion in Canada under climate change: Evaluating evolutionary potential. Can. J. Plant Sci. 92: 1013-1020. Many weed species have already advanced northward from the United States into Canada, and their number threatens to increase with warming trends under climate change. For many weed species, this range expansion can be attributed to evolutionary adaptation by northern populations occurring in areas experiencing warmer climates and longer growing seasons in recent decades. In this paper, we examine the potential for invasive plant species to be selected for one or more of 10 character traits: (1) high growth rate, (2) wide climatic or environmental tolerance, (3) short generation time, (4) prolific or consistent reproduction, (5) small seed size, (6) effective dispersal, (7) uniparental reproduction capacity, (8) no specialized germination requirements, (9) high competitive ability, and (10) effective defenses against natural enemies. If any one of these traits is selected for in an invasive species, it would provide the affected species with the potential for a more expansive invasion range than anticipated by models that assume a static genotype. Four weed species of interest exhibiting potential northward range expansion within North America were evaluated: an obligatory outcrossing annual dicot, Himalayan balsam (Impatiens glandilifera Royle), a mostly selfing annual dicot, velvetleaf (Abutilon theophrasti Medic.), a perennial dicot that reproduces via rhizomes but forms fertile hybrids, Japanese knotweed [Fallopia japonica (Houtt.) Ronse Decr.], and a primarily selfing perennial grass, johnsongrass [Sorghum halapense (L.) Pers.]. Evidence for potential evolutionary responses to climate change was observed among particular traits for each of the four species, despite population genetic differences. The population genetics of invasive plants are difficult to model, as is climate change itself, but consideration of weed evolution to whatever degree possible should lead to improved predictive power of such models.

Neri, D., Baruzzi, G., Massetani, F. and Faedi, W. 2012. Strawberry production in forced and protected culture in Europe as a response to climate change. Can. J. Plant Sci. 92: 1021-1036. In Europe, the production of strawberry for fresh market in forced and protected conditions is increasing. These techniques were initially aimed at enhancing the earliness of June-bearing short day varieties. Nowadays, the objective is to have year-round fruit availability, forcing and preserving strawberry crops against adverse weather conditions. The new high-quality low-chilling varieties widely expanded winter-spring strawberry production in the Mediterranean climate with autumn planting, while the diffusion of day-neutral ever-bearing varieties increased spring-summer yields in more continental climates, avoiding the extremely cold winter with spring planting. Finally, the use of tray-plants significantly increased late summer-fall strawberry production with summer programmed planting. The present review analyzes the recent evolution of strawberry cultivars and cultivation systems under plastic tunnels and in greenhouses. The physiological effects on plant architecture and propagation are discussed. In conclusion, we can affirm that strawberry growers are facing climate change with innovations in cultivated varieties and cultural techniques, and by the integration of the different production areas, with their specific optimum yield seasons, to continuously fulfill the demands of the European market.

Ghazvini, H., Hiebert, C. W., Zegeye, T. and Fetch, T. 2012. Inheritance of stem rust resistance derived fromAegilops triuncialisin wheat line Tr129. Can. J. Plant Sci. 92: 1037-1041. Stem rust, caused by Puccinia graminis f. sp. tritici (Pgt), is a devastating disease of wheat that can cause serious grain yield reduction. The emergence of Pgt race TTKSK (Ug99) and new variants in Africa is considered a threat to wheat production worldwide. Among the primary gene pool of wheat, only a few stem rust resistance (Sr) genes confer resistance to TTKSK. Wild relatives of common wheat are an important source of disease resistance. A preliminary study indicated that the common wheat line Tr129, which contains one or more Aegilops triuncialis translocations, is resistant to race TTKSK. The goal of this study was to elucidate the inheritance of resistance to Pgt in line Tr129 and investigate the novelty of the gene(s) conferring resistance. A population was generated by crossing RL6071 with Tr129 and F₂ and F₃ progeny were inoculated with Pgt race MCCF at the first leaf stage. Segregation of F₂ plants fit a 15:1 ratio ( =1.48, P=0.22) indicating two dominant genes in Tr129 conditioned stem rust resistance to race MCCF. Segregation of F₃ families also fit a 7:8:1 ratio (= 3.28, P=0.19) confirming the presence of two dominant genes. This is first report of stem rust resistance transferred to wheat from Ae. triuncialis.

Schellenberg, M. P., Biligetu, B., McLeod, G. J. and Wang, Z. 2012. Phenotypic variation of side-oats grama grass [Bouteloua curtipendula (Michx.) Torr.] collections from the Canadian prairie. Can. J. Plant Sci. 92: 1043-1048. Native prairie grasses are adapted to local climates and have the potential for development as forage grass cultivars for semiarid environments. Side-oats grama grass [Bouteloua curtipendula (Michx.) Torr.] is a drought-tolerant grass with desirable forage characteristics, and is distributed across the Canadian prairies and throughout the Great Plains. Understanding ecotypic variability of this species is a prerequisite for developing populations suitable for drier regions of western Canada. A randomized complete block field plot was established using nine seed collections from Manitoba and Saskatchewan in 2006 near Swift Current (lat. 50°25′N, long. 107°44′W), Canada. Seed yield, tiller number, plant height, foliage diameter, and days to flower of individual plants were measured for each collection in the summers of 2007 and 2010. The Sidney and Wolseley collections had taller plants with greater basal diameter. Plants from these two collections also had higher tiller number, and required fewer days to reach flowering stage. However, there was no clear ranking of these variables among other collections. Averaged flowering date was Aug. 15 for Alexander, Sidney, and Wolseley collections, Aug. 21 for Wellwood, Glenboro, and Pratt collections, and Aug. 26 for Minto and Coulter collections, respectively. Taller plants with greater tiller number for the Sidney and Wolseley collections showed a potential for further cultivar development.

Baig, M. M. Q., Hafiz, I. A., Abbasi, N. A., Yaseen, M., Akram, Z. and Donnelly, D. J. 2012. Reduced-statureRosaspecies through in vitro mutagenesis. Can. J. Plant Sci. 92: 1049-1055. Plant height is one of the main attributes affecting general appeal and beauty of roses (Rosa spp.). Among the highly scented rose species, R. gruss an teplitz, R. centifolia, and R. borboniana, have great potential horticultural and commercial value. However, their large plant size detracts from recent trends towards selection of smaller plants for emerging markets and high-density plantations. This study aimed to produce reduced-stature plants through in vitro mutagenesis using gamma irradiation (Co₆₀). Shoot tips cut from micropropagated shoots were exposed up to 120 Gy. Irradiated shoot tips were micropropagated for one culture cycle. Surviving shoots were rooted in vitro then acclimatized for 2 mo in a greenhouse. The shoot tip LD₅₀ after gamma irradiation was species-dependent and 33-54 Gy. In this dose range, survival during in vitro rooting and acclimatization was also affected; this was 64 to 24% and 34 to 14% of control values, respectively. Acclimatized transplants were 17 to 56% smaller with 16 to 51% less leaf area compared with the controls. In order to ascertain stability putative reduced-stature roses will be monitored for vegetative and floral characteristics over the next few years. This study adds to the ongoing efforts to obtain reduced-stature rose plants for horticultural purposes.

Yadav, I. S. and Singh, N. P. 2012. An effective protocol for improved regeneration capacity of Kabuli chickpeas. Can. J. Plant Sci. 92: 1057-1064. An efficient protocol for in vitro regeneration is essential for genetic manipulation and micro-propagation of important plant species. A direct shoot regeneration system has been optimized for Desi chickpeas, but an effective regeneration protocol is still needed for Kabuli chickpeas. An efficient regeneration protocol for Kabuli chickpeas was developed, using whole embryonic axes, an embryonic axes slice and cotyledonary node explants from two genotypes L550 and JGK-1. Depending upon chickpea genotype, type of explant and culture medium, percentage of shoot producing explants (frequency) and the number of shoots per explant (efficiency) varied from 10 to 83% and from 1 to 58, respectively. The shoot regeneration capacity (SRC=frequency×efficiency), which is an indicator of the effectiveness of the protocol, varied from 47 to 2508 shoots per 100 explants cultured. On average, SRC of L550 was 1.8 times higher than JGK-1. Murashige and Skoog's (MS) medium B5 vitamins supplemented with 8.0 µM benzyl amino purine (BAP) 0.5 µM a- naphthalene acetic acid (NAA) and 0.1 M sucrose plus embryonic axes was found to be the most effective culture medium and type of explants, respectively. Half strength MS medium 2% sucrose supplemented with 4 µM NAA, 3µ M IAA or 4µM IAA produced a high rooting percentage in both chickpea genotypes. The regeneration process starting from explant preparation to establishment of a complete plant in soil took 105-110 d. This optimized regeneration method holds promise for facilitating the insertion of interested genes through genetic transformation for improvement of Kabuli chickpeas.

Debnath, S. C., Vyas, P., Goyali, J. C. and Igamberdiev, A. U. 2012. Morphological and molecular analyses in micropropagated berry plants acclimatized under ex vitro condition. Can. J. Plant Sci. 92: 1065-1073. Berry crops include, but are not limited to, the members of the genera Fragaria (strawberry; Rosaceae), Rubus (brambles: raspberry and blackberry; Rosaceae), Vaccinium (blueberry, cranberry and lingonberry; Ericaceae) and Ribes (currant and gooseberry; Grossulariaceae). While berry fruits have long enjoyed huge popularity among consumers, tremendous progress in plant tissue culture, resulting in great advances in micropropagation, has occurred. The in vitro morphogenesis seems to be highly dependent on plant growth regulators and media used for culture, which is again genotype specific. Although automation of micropropagation in bioreactors has been advanced as a possible way of reducing the cost of propagation, optimal plant production depends on better understanding of physiological and biochemical responses of plants to the signals of the culture microenvironment and an optimization of specific physical and chemical culture conditions to control the morphogenesis of berry plants in liquid culture systems. Increased branching, vigorous vegetative growth and change in biochemical components are often noted in micropropagated plants acclimatized under ex vitro condition. Clonal fidelity can be a serious problem and strategies have been developed to reduce the variation to manageable levels. Molecular markers have been introduced in tissue culture research and can potentially be used in various facets of pertinent studies with berry crops. This paper describes in depth the progress of various aspects of berry propagation in vitro, the characterization of micropropagated berry plants for morphological characters, and the employment of molecular markers in these plants for the assessment of genetic fidelity, uniformity, stability and trueness-to-type among donor plants and tissue culture regenerants.

Ahmad, S., Singh, M., Lamb-Palmer, N. D., Lefsrud, M. and Singh, J. 2012. Assessment of genetic diversity in 35Pisum sativumaccessions using microsatellite markers. Can. J. Plant Sci. 92: 1075-1081. Field pea is an important Canadian pulse crop and therefore developing high-performing cultivars is critical for Canadian pea growers. Information about genetic diversity is a key component for the creation of novel and desirable germplasm to develop elite pea breeding lines. The objective of the present study is to assess genetic diversity in 35 diverse Pisum accessions using 15 polymorphic microsatellites located on different pea chromosomes. Microsatellites were found to be polymorphic, amplifying a total of 41 alleles and were able to differentiate all 35 Pisum genotypes. These markers were scored by their polymorphic information content (PIC), ranging from 0.055 (AA206) to 0.660 (AB72) with an average of 0.460, and by their discriminating power (D), which varied from 0.057 (AA206) to 0.679 (AB 72) with an average of 0.475. Genetic similarity values ranged from 0.074 (between Maple pea NZ and Line 45760) to 0.875 (between Galena and Dakota) with an average of 0.336. Unweighted pair group method with arithmetic averages (UPGMA) cluster analysis grouped the 35 pea accessions into two major clusters and eight sub-clusters. The majority of Canadian and European genotypes were grouped separately, suggesting both these groups are from genetically distinct gene pools. The genetically diverse groups identified in this study can be used to derive parental lines for pea breeding.

Andronic, L. 2012. Viruses as triggers of DNA rearrangements in host plants. Can. J. Plant Sci. 92: 1083-1091. Assessment of microsporogenesis in tomato (Lycopersicon esculentum, cultivars Fachel, Nistru and Prizior) infected with tomato aspermy virus or potato virus X and barley (Hordeum vulgare L., cultivars Galactic, Sonor, Unirea) infected with barley stripe mosaic virus showed deviations in the conjugation of homologous chromosomes and segregation of genetic material, expressed in the disruption of chromatin cohesion between homologous chromosomes. The evidence of meiotic division in targeted genotypes indicates the effect of viral infection on chiasmata number and position, promoting the redistribution of chiasmata. On the basis of cytological study, significant changes and the induction of additional exchanges offset by asynapsis were established in early diakinesis. Different parameters, determined at particular stages of meiosis, such as chromosome aberration and the mean percentage of abnormal pollen mother cells, served as cytogenetic evaluation of microsporogenesis in virus-infected tomato or barley cultivars. The study of meiotic stability in anaphase and telophase I and II revealed a significant increase in different types of abnormalities: elimination or/and lagging chromosomes, formation of chromosome and chromatid bridges with or without fragments. Reviewed examples provide data regarding genetic rearrangements in host plants as a response to viral infection.

Morrison, M. J., Frégeau-Reid, J. A. and Cober, E. R. 2012. Genotype and environment influence gamma aminobutyric acid concentration in short-season soybean. Can. J. Plant Sci. 92: 1093-1100. Gamma aminobutyric acid (GABA) is a four-carbon, non-structural protein found ubiquitously in life forms on the planet. In plants, it is produced in the cytosol in response to stresses, via the α-decarboxylation of glutamate by the enzyme glutamate decarboxylase. In studies, foods made from soybean (Glycine max L. Merr), with high GABA concentration, have reduced high blood pressure. Our objective was to determine if there were genotypic differences for GABA concentration among a series of short-season soybean cultivars. A historical series of 16 cultivars released from 1934 to 2000 was grown in a randomized complete block design with four replications across 3 yr at the Central Experimental Farm in Ottawa, Canada. Seed was harvested for yield and a sample taken to determine seed weight, protein, oil, L-glutamate (L-Glu) and GABA concentrations. There were significant differences among cultivars for all parameters and significant differences among years for all parameters except L-Glu. GABA was positively correlated with protein concentration, L-Glu and seed yield. There was a threefold difference in GABA concentration between the highest and lowest cultivars, but no clear relationships to weather parameters were identified. GABA concentration was determined to be moderately heritable (44%) indicating that new cultivars with higher concentrations could readily be developed. Soybean cultivars with higher GABA concentration, as part of the diet, may provide a means to reduce or prevent hypertension.

Li, H., Tsao, R. and Deng, Z. 2012. Factors affecting the antioxidant potential and health benefits of plant foods. Can. J. Plant Sci. 92: 1101-1111. Phytochemicals, such as carotenoids, phenolics and glucosinolates, in plants and plant-based foods are able to reduce the incidence of non-communicable diseases such as cardiovascular diseases, diabetes, stroke and different types of cancer due to their antioxidant potential. A brief summary of the in vitro and in vivo evidence and how post-harvest storage and processing conditions can affect the health benefits is presented in this review. Genetic, environmental conditions and physiological factors may modify the composition and amounts of these compounds present in plants, thus affecting the in vitro antioxidant activities. Such changes in combination with degradations after digestion can significantly affect the bioaccessibility and bioavailability of phytochemicals. The main objective of this review is to provide updated information on the effects of various factors such as genetics, environment, post-harvest storage and processing on the bioactive components, and knowledge of these factors can lead to multidisciplinary strategies to maximise the bioavailability and health potential of foods.

Yu, L. J. and Rupasinghe, H. P. V. 2012. Effect of acidification on quality and shelf-life of carrot juice. Can. J. Plant Sci. 92: 1113-1120. This study compared the effects of different acidification methods for processing carrot juice: blanching of carrot with 20 and 40 g L^-1 of citric acid, 20 and 40 g L^-1 of lactic acid and blending carrot juice with cranberry juice in 80:20 and 70:30 ratios. The quality was measured in terms of changes in pH, titratable acidity (TA), total soluble solids (TSS), turbidity, antioxidant capacity, beta-carotene content and total aerobic colony count (TAC) during a 21-d storage at 4°C. Water blanched carrot juice was selected as the control. During storage, the pH, TA, TSS and turbidity values were much more stable for all acidified juices than for water blanched juice. The highest value and stability of antioxidant capacity measured by ferric reducing antioxidant power (FRAP) belonged to a carrot-cranberry juice blend in a 70:30 ratio. The highest beta-carotene value belonged to 40 g L^-1 lactic acid blanched juices. Carrot-cranberry juice blend in an 80:20 ratio gave the maximum stability for beta-carotene. All acidification methods prolonged the shelf-life of carrot juice in terms of TAC. Blanching with 40 g L^-1 of lactic acid or citric acid provided 3-4 log reduction TAC and was among the most effective methods for extending the shelf-life of carrot juice.

Debnath, S. C., Siow, Y. L., Petkau, J., An, D. and Bykova, N. V. 2012. Molecular markers and antioxidant activity in berry crops: Genetic diversity analysis. Can. J. Plant Sci. 92: 1121-1133. An improved understanding of important roles of dietary fruits in maintaining human health has led to a dramatic increase of global berry crop production. Berry fruits contain relatively high levels of vitamin C, cellulose and pectin, and produce anthocyanins, which have important therapeutic values, including antitumor, antiulcer, antioxidant and anti-inflammatory activities. There is a need to develop reliable methods to identify berry germplasm and assess genetic diversity/relatedness for dietary properties in berry genotypes for practical breeding purposes through genotype selection in a breeding program for cultivar development, and proprietary-rights protection. The introduction of molecular biology techniques, such as DNA-based markers, allows direct comparison of different genetic materials independent of environmental influences. Significant progress has been made in diversity analysis of wild cranberry, lowbush blueberry, lingonberry and cloudberry germplasm, and in strawberry and raspberry cultivars and advanced breeding lines developed in Canada. Inter simple sequence repeat (ISSR) markers detected an adequate degree of polymorphism to differentiate among berry genotypes, making this technology valuable for cultivar identification and for the more efficient choice of parents in the current berry improvement programs. Although multiple factors affect antioxidant activity, a wide range of genetic diversity has been reported in wild and cultivated berry crops. Diversity analysis based on molecular markers did not agree with those from antioxidant activity. The paper also discusses the issues that still need to be addressed to utilize the full potential of molecular techniques including expressed sequence tag-polymerase chain reaction (EST-PCR) analysis to develop improved environment-friendly berry cultivars suited to the changing needs of growers and consumers.

Percival, D., Kaur, J., Hainstock, L. J. and Privé, J.-P. 2012. Seasonal changes in photochemistry, light use efficiency and net photosynthetic rates of wild blueberry (Vaccinium angustifolium Ait.). Can. J. Plant Sci. 92: 1135-1143. The seasonal variation of carotenoid concentration, chlorophyll a and b levels, dark- (Fv/Fm) and light-adapted (Fv'/Fm') variable to maximal chlorophyll fluorescence (an indication of the quantum efficiency of PSII photochemistry) and net photosynthesis of the wild blueberry (Vaccinium angustifolium Ait.) was examined in the vegetative and cropping phases of production. Chlorophyll levels ranged from 2.0 to 12 µg cm^-2 and from 0.042 to 1.4 µg cm^-2 for chlorophyll a and b, respectively, were significantly lower in the cropping phase of production, and were also lower in the latter stages of the growing season. Similarly, carotenoid concentrations ranged from 0.67 to 4.1 µg cm^-2 and were lower in the cropping phase of production. However, carotenoid concentration and dark- and light-adapted variable to maximal chlorophyll fluorescence (Fv/Fm and Fv'/Fm') decreased marketably at the mid-point of the growing season, presumably as a result of photoinhibition. Net photosynthetic values of upright stems ranged from 2.1 to 7.6 µmol m^-2 s^-1, were substantially higher in the vegetative phase of production and also decreased significantly in the latter part of the growing season. Results from this investigation indicate that the wild blueberry has a relatively low photosynthetic rate, which may be prone to photoinhibition and limited carbohydrate supply (i.e., source) when compared with other temperate fruit crops.

Kaur, J., Percival, D., Hainstock, L. J. and Privé, J.-P. 2012. Seasonal growth dynamics and carbon allocation of the wild blueberry plant (Vaccinium angustifoliumAit.). Can. J. Plant Sci. 92: 1145-1154. Field studies were conducted at the Wild Blueberry Research Station, Debert, NS, to examine the carbon allocation dynamics within the wild blueberry (Vaccinium angustifolium Ait.). This was achieved with biweekly measurements of dry weight, soluble sugar and starch levels of the rhizomes, roots, stems/leaves and berries of plants in the vegetative (i.e., sprout phase) and cropping phases of production. Non-structural carbohydrate levels were determined using high-performance liquid chromatography (HPLC). Growth parameters included phenology, stem height, dry weights of the above-ground vegetation (stems and leaves), berries, rhizomes and roots. Interestingly, root growth was observed prior to upright shoot emergence and dry weight for rhizome remained higher compared with stems and leaves. The rhizomes acted as a carbohydrate source during stem and root growth. The developing berry crop appeared to be a strong sink for photo-assimilates, as berries were found to import sucrose and convert it to fructose and glucose during maturation, and HPLC studies further confirmed the increasing levels of fructose and glucose. Given the phenology of the wild blueberry, the results exemplify the importance of the rhizomes as a strong carbohydrate source, especially in the early stages of a growing season when the carbohydrate production is limited.

Maqbool, R., Percival, D. C., Adl, M. S., Zaman, Q. U. and Buszard, D. 2012. In situ estimation of foliar nitrogen in wild blueberry using reflectance spectra. Can. J. Plant Sci. 92: 1155-1161. Remote sensing techniques have the potential to serve as an important nutrient management tool in wild blueberry. The potential of visible (VIS), near infrared (NIR) and shortwave infrared (SWIR) spectroscopy was evaluated during 2006 (sprout/vegetative phase of production) to estimate foliar nitrogen (N). Canopy reflectance measurements were taken from two nutrient management experimental sites located in Nova Scotia (NS) and New Brunswick (NB). Partial least squares regression (PLSR) estimated foliar N, giving the coefficients of determination (R²) values ranging from 0.69 to 0.85, and root mean square errors of cross validation (RMSECV) from 0.16% (±8.29% of mean) to 0.24% (±12.43% of mean) for different spectral ranges used in this study. The green peak region located in the VIS region best estimated foliar N. The tested spectral ranges differed in their predictive ability, but generally followed the biochemical basis. Variable importance in projection scores (VIP), regression vector coefficients and PLSR loading weights (LWs) plots highlight the importance of wavebands (∼550 nm, ∼610 nm, 1510 nm, ∼1690 nm, ∼1730 nm, ∼1980 nm and ∼2030 nm) for in situ foliar N estimations. Thus, it was concluded that reflectance spectra may be used to estimate and ultimately map foliar N in wild blueberry production. The results illustrated the ability of multivariate techniques, such as PLSR to explore hyperspectral data and estimate leaf tissue nutrient content.

Thilakarathna, R. M. M. S., Papadopoulos, Y. A., Rodd, A. V., Gunawardena_, A. N., Fillmore, S. A. E. and Prithiviraj, B. 2012. Characterizing nitrogen transfer from red clover populations to companion bluegrass under field conditions. Can. J. Plant Sci. 92: 1163-1173. The ability of two red clover (Trifolium pratense L.) cultivars, AC Christie (diploid) and Tempus (tetraploid), to transfer fixed nitrogen (N) to companion bluegrass (Poa pratensis L.) was evaluated under field conditions. Plant samples were harvested three times during the 2009 growing season and N transfer from the red clover cultivars to bluegrass was determined using the natural abundance method for first harvest and ¹⁵N dilution techniques for second and third harvests. Soil and soil water samples were used to evaluate cultivar effects on soil N conditions. Both red clover cultivars derived more than 90% of their N from biological N fixation. The proportion of bluegrass N derived from interplant N transfer was 7, 11, and 26% for the first, second, and third harvests, respectively. Soil KCl extractable nitrate increased along the three cuts for Tempus in the 0 to 15-cm soil zone. Soil-water nitrate content increased periodically for AC Christie and remained constant for Tempus throughout the growing season. This result indicates that the two cultivars have distinctly different N cycling patterns.

Hwang, S. F., Cao, T., Xiao, Q., Ahmed, H. U., Manolii, V. P., Turnbull, G. D., Gossen, B. D., Peng, G. and Strelkov, S. E. 2012. Effects of fungicide, seeding date and seedling age on clubroot severity, seedling emergence and yield of canola. Can. J. Plant Sci. 92: 1175-1186. The infestation of seeds by Plasmodiophora brassicae can result in the transmission of clubroot disease in canola. Five fungicides, including Dynasty 100 FS (azoxystrobin), Helix Xtra (thiamethoxam difenoconazole metataxyl fludioxonil), Nebijin^TM 5SC (flusulfamide), Prosper FX (clothianidin carbathiin trifloxystrobin metalaxyl), and Vitavax RS (carbathiin thiram), were evaluated under greenhouse conditions using artificially infested canola seeds for their efficacy in eliminating seed-borne inoculum. All of the fungicides significantly reduced clubroot relative to the non-treated control, but Nebijin^TM 5SC and Dynasty 100 FS were the most effective. However, in field trials with Cruiser 5 FS (thiamethoxam), Helix Xtra, Dynasty, Prosper and Sedaxane (pyrazole anilide) applied alone or as a mixture, none of the treatments reduced clubroot severity or improved seedling emergence or yield compared with the insecticidal control (Cruiser 5 FS) in the susceptible cultivar. Clubroot severity was lower in early-seeded canola compared with the late-seeded crops in 2 site-years. The younger seedlings had greater disease severity and reduced plant height and yield than did older seedlings in both resistant and susceptible canola cultivars. We conclude that a combination of approaches including seed treatments and manipulation of seeding dates in conjunction with deployment of resistant cultivars is necessary for the sustainable management of clubroot in canola.

Bélanger, G., Savoie, P., Parent, G., Claessens, A., Bertrand, A., Tremblay, G. F., Massé, D., Gilbert, Y. and Babineau, D. 2012. Switchgrass silage for methane production as affected by date of harvest. Can. J. Plant Sci. 92: 1187-1197. Switchgrass (Panicum virgatum L.) is a warm-season grass recognized as a potential biomass crop for energy production in North America, but little information exists on the effect of harvest date on forage and silage characteristics of switchgrass grown in eastern Canada. Our objectives were to determine how harvest date affects several forage and silage characteristics of switchgrass and to relate these to specific methane yield from anaerobically digested switchgrass silage. Switchgrass, seeded in 2002 and 2006, was harvested and ensiled as a one-cut system on three dates in 2007: late July, early September, and early October. The regrowth from the late July harvest was also harvested in early October as a two-cut system. Silage quality parameters [pH, and concentrations of N, N-NH₃, total amino acids (TAA), and volatile fatty acids (VFA)] indicated adequate fermentation of all silage samples. In a one-cut system, delaying harvest from late July to early September increased forage dry matter (DM) yield from 9.0 to 11.5 Mg ha^-1, forage soluble carbohydrate (SC) concentration from 51 to 85 g kg^-1 DM, and silage SC concentration from 13 to 25 g kg^-1 DM; delaying harvest from late July to early October decreased forage in vitro true digestibility (IVTD) from 720 to 582 g kg^-1 DM, forage in vitro digestibility of the neutral detergent fibre (dNDF) from 590 to 409 g kg^-1 DM, and silage acetate concentration from 7.7 to 2.6 g kg^-1 DM. The regrowth had higher IVTD and dNDF, lower acid detergent fibre concentration, and higher silage lactate and acetate concentrations than a single harvest taken in early September or early October. The two-cut system and the single harvest in early September produced the highest seasonal forage DM yields (11.5 and 11.9 Mg ha^-1). High specific methane yield was (i) correlated with low forage fibre concentration and high DM digestibility and (ii) more correlated to silage concentrations of lactate and acetate than to silage SC concentration.

Papadopoulos, Y. A., McElroy, M. S., Fillmore, S. A. E., McRae, K. B., Duyinsveld, J. L. and Fredeen, A. H. 2012. Sward complexity and grass species composition affects the performance of grass-white clover pasture mixtures. Can. J. Plant Sci. 92: 1199-1205. The productivity of managed permanent pastures is closely associated with the species composition of seeded mixtures. Ecological theory suggests that increasing plant species' diversity will result in higher productivity, resilience, and resistance to invasive species. To better understand the relationship between sward species composition and pasture productivity, mixtures of four common pasture grass species, timothy (Phleum pratense L.), Kentucky bluegrass (Poa pratensis L.), reed canarygrass (Phalaris arundinacea L.), and meadow fescue (Festuca pratensis L.), were seeded in 2004 in binary (two-grass), tertiary (three-grass), and quaternary (four-grass) combinations with white clover (Trifolium repens L.). Plots were rotationally grazed for 5 yr, with yield determined in the first post-establishment year (2005) and in 3 subsequent production years (2007, 2008, and 2009). Mean dry matter yield (DMY) increased appreciably from post-establishment (3801 kg ha^-1) to the production years (6613 kg ha^-1). Contrasts revealed significantly higher DMY production in quaternary mixtures versus less complex plots in production years. Repeated measure analysis found significant quadratic trends in DMY for plots containing bluegrass and timothy, showing different patterns of growth between the respective mixtures. Principal component analysis (PCA) of averaged yields over the production years revealed a strong association between seeded grass growth and DMY. This relationship between DMY and seeded grass growth was strongest in swards containing a combination of timothy and bluegrass. In general, the growth of unseeded grasses and forbs increased in mixtures with large proportions of timothy and reed canarygrass. In spite of the fact that mixtures containing timothy and bluegrass were shown to produce high DMY, it appears the aggressiveness of bluegrass suppressed the yield potential of timothy. White clover yields and unseeded grasses/forbs were both significantly lower in mixtures containing bluegrass. Also, the PCA revealed a favourable compatibility between meadow fescue and white clover growth, while bluegrass appears to suppress meadow fescue growth. Results show that species complexity increases sward productivity over the long term, and that the presence of two grass species, in particular (timothy and bluegrass), has considerable influence on DMY.

MacDonald, J. E., Hacking, J., Weng, Y. and Norrie, J. 2012. Root growth of containerized lodgepole pine seedlings in response to Ascophyllum nodosum extract application during nursery culture. Can. J. Plant Sci. 92: 1207-1212. Vigorous root growth immediately after spring planting is crucial to ensure a well-developed root system before the occurrence of drought events associated with climate change. The objective of this study was to enhance spring root growth of containerized lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) seedlings. Seedling culture began in April. In September, seedlings were root drenched with an extract of the brown marine alga Ascophyllum nodosum (L.) Le Jolis in finisher fertilizer at rates of 1:750, 1:500, and 1:250. Finisher fertilizer alone served as control. Applications were made three or six times. Seedling culture continued until lifting in December, and then seedlings were freezer stored. Frequency of application had no effect on root growth, whereas rate of application had a significant effect. Compared with control, the 1:750, 1:500, and 1:250 rates significantly reduced total length of the root system in mid October. After overwintering and growing under favorable environmental conditions for 21 d, the 1:500 rate significantly increased the total number of white roots, as well as the number of both short and long white roots. These results suggest that application of Ascophyllum nodosum extract may be a valuable nursery practice to increase spring root growth, thereby enhancing drought resistance.

Ma, B. L., Biswas, D. K., Zhou, Q. P. and Ren, C. Z. 2012. Comparisons among cultivars of wheat, hulled and hulless oats: Effects of N fertilization on growth and yield. Can. J. Plant Sci. 92: 1213-1222. There is limited comparative research on the responses of crop growth and yield to N fertilization in hulless (Avena nuda) and hulled (Avena sativa) oats. A field study was conducted for 3 yr at Ottawa, ON, to assess the growth and grain yield of current wheat (Triticum aestivum), hulled and hulless oat cultivars with three N fertility levels. Averaged across the 3 yr, both the mid and high (75 and 150 kg N ha^-1) N treatments demonstrated statistically similar, but higher, leaf area index (LAI) and total dry matter (TDM) than the 0 N treatment, regardless of crop types. At final harvest, with increasing N supply, both hulled oat Gosling and wheat cultivar AC Brio had similar and higher TDM than the hulless oat VAO-2 in 2006, whereas both oat cultivars produced much lower (P<0.01) grain yield than wheat in 2008, primarily due to early lodging of the oat cultivars. Overall, the wheat cultivar AC Brio produced the greatest grain yield with the highest harvest index (HI), followed by hulled Gosling; the hulless oat had the lowest grain yield and the lowest HI. Compared with the wheat cultivar, the lower grain yield of both hulled and hulless oats was attributed to a lower (P<0.05) HI and more severe crop lodging (especially when lodging occurred early), coupled with a higher LAI at flowering. Our results suggest that enhancing HI and resistance to crop lodging are the primary targets for both the hulled and hulless oat cultivar improvement in eastern Canada.

Sanderson, K. R. and Fillmore, S. A. E. 2012. Slow-release nitrogen fertilizer in carrot production on Prince Edward Island. Can. J. Plant Sci. 92: 1223-1228. The impact of nitrogen management using slow-release fertilizers has not been examined for carrot (Daucus carota L.) production in Atlantic Canada. To assess the effects of such products, we evaluated five slow-release fertilizers over a 3-yr period. Treatments consisted of sulphur coated urea (SCU) (42-0-0), isobutylidene diurea (IBDU) (31-0-0), Nutralene^® (methylene urea) (40-0-0), Sirflor^® (urea formaldehyde) (38-0-0), UFLEXX™ (urea, dicyandiamide, N-(n-butyl) thiophosphoric triamide) (46-0-0) compared with industry standard (ammonium nitrate) (34-0-0). All slow-release fertilizer treatments supplied N at 50 kg N ha^-1 pre-plant. Slow-release fertilizer treatments were compared with the industry standard of 50 kg N ha^-1 pre-plant plus 50 kg N ha^-1 as a top dress. UFLEXX™ increased biological and marketable yield by 7.5 and 18.7%, respectively, compared with the industry standard. Sirflor^® produced the lowest yield. GreenSeeker^® NDVI reading and LECO N were correlated at the mid-season sample. GreenSeeker^® technology has potential as an in-field crop health assessment tool, however, further research is required to develop GreenSeeker^® algorithms appropriate for carrot production in Prince Edward Island.