Yadav, A. K., Singh, S., Dhyani, D. and Ahuja, P. S. 2011. A review on the improvement of Stevia [Stevia rebaudiana (Bertoni)]. Can. J. Plant Sci. 91: 1-27. Stevia rebaudiana (Bertoni) is a herbaceous perennial plant (2n=22) of genus Stevia Cav., which consists of approximately 230 species of herbaceous, shrub and sub-shrub plants. Leaves of stevia produce diterpene glycosides (stevioside and rebaudiosides), non-nutritive, non-toxic, high-potency sweeteners and may substitute sucrose as well as other synthetic sweetners, being 300 times sweeter than sucrose. In addition to its sweetening property, it has medicinal values and uses. Stevia is self-incompatible plant and the pollination behaviour is entomophilous. Rebaudioside-A is of particular interest among the glycosides produced in the leaves of stevia because of the most desirable flavour profile, while, stevioside is responsible for aftertaste bitterness. Development of new varieties of S. rebaudiana with a higher content of rebaudioside-A and a reduced content of stevioside is the primary aim of plant breeders concerned with the improvement and utilization of this source of natural sweeteners. The proportions of rebaudioside-A and -C are controlled by a single additive gene known to be co-segregating suggesting synthesis by the same enzyme. Stevioside and rebaudioside-A are negatively correlated, while rebaudioside-A and -C are positively correlated. Conventional plant breeding approaches such as selection and intercrossing among various desirable genotypes is the best method for improving quality traits in a highly cross-pollinated crop like stevia. Various plant types with larger amounts of specific glycoside have already been patented, such as RSIT 94-1306, RSIT 94-75, RSIT 95-166-1 through selection and intercrossing. Composites and synthetics can be used to capture part of the available heterosis because of the high degree of natural out-crossing and the absence of an efficient system of pollination control. Synthetics and composites like “AC Black Bird“ and “PTA-444“ have already been developed. Polyploidy results in better adaptability of individuals and increased organ and cell sizes. Tetraploids have larger leaf size, thickness and have potential use in increasing biomass and yield in comparison with diploid strains. Characters of interest with low variability in the population may be improved through mutation breeding. Use of biotechnological approaches, such as tissue culture for the mass propagation of elite genotypes, anther culture for development of pure homozygous doubled haploid and molecular marker technology for identification of marker loci linked to rebaudioside-A trait, can create new opportunities for plant breeders. Understanding the mechanism and pathway of biosynthesis of steviol glycosides can help to improve the glycoside profile by up-regulation and down-regulation of genes.

Pageau, D. and Lajeunesse, J. 2011. Effect of seeding date on oilseed flax grown in a cool climate. Can. J. Plant Sci. 91: 29-35. In Quebec, the growing season is relatively short and most crops are sown early in the spring. However, flax (Linum usitatissimum L.) production is recent in Quebec and the effect of time of seeding on flax productivity has not yet been studied. The objective of this project was to determine the effect of four different sowing dates on the productivity of oilseed flax grown in a cool climate in Quebec. Four planting dates (mid-May to mid-June) were evaluated for 4 yr (2004, 2006, 2007 and 2008) with four cultivars (AC Emerson, AC McDuff, CDC Bethune and Lightning). During 2 yr, delays in seeding reduced grain yields. Moreover, in 2006 and 2007, flax seeded at the last planting date (mid-June) did not reach maturity. Compared with the earliest seeding date, a 2-wk delay in sowing reduced grain yields by 34 to 42% in 2006 and by 25 to 51% in 2007. Late sowing also reduced the oil content and 1000-grain weight of flax. These results indicate that oilseed flax should be sown early (11-18 May) in regions where the climate is cool.

Cogliatti, M., Bongiorno, F., Dalla Valle, H. and Rogers, W. J. 2011. Canaryseed (Phalaris canariensis L.) accessions from nineteen countries show useful genetic variation for agronomic traits. Can. J. Plant Sci. 91: 37-48. Fifty-seven accessions of canaryseed (47 populations and 10 cultivars) from 19 countries were evaluated for agronomic traits in four field trials sown over 3 yr in the province of Buenos Aires, Argentina. Genetic variation was found for all traits scored: grain yield and its components (grain weight, grain number per square meter, grain number per head and head number per square meter), harvest index, percent lodging, and phenological characters (emergence to heading, emergence to harvest maturity and heading to harvest maturity). Although genotype×environment interaction was observed for all traits, the additive differences between accessions were sufficient to enable promising breeding materials to be identified. Accessions superior in performance to the local Argentinean population, which in general gave values close to the overall mean of the accessions evaluated, were identified. For example, a population of Moroccan origin gave good yield associated with elevated values of the highly heritable character grain weight, rather than with the more commonly observed grain number per square meter. This population was also of relatively short stature and resistant to lodging, and, although it performed best when sown within the normal sowing date, tolerated late sowing fairly well. Other accessions were also observed with high grain weight, a useful characteristic in itself, since large grains are desirable from a quality point of view. Regarding phenology, the accessions showed a range of 160 degree days (8 calendar days in our conditions) in maturity, which, while not large in magnitude, may be of some utility in crop rotation management. Some accessions were well adapted to late sowing. Grain yield in general was strongly correlated with grain number per square meter. Principal components analysis (PCA) carried out for all characteristics provided indications of accessions combining useful characteristics and identified three components that explained approximately 70% of the phenotypic variation. Furthermore, a second PCA plus regression showed that approximately 60% of the variation in grain yield could be explained by a component associated with harvest index and grain number per square meter. Pointers were provided to possible future breeding targets.

Hossain, S., Panozzo, J. F., Pittock, C. and Ford, R. 2011. Quantitative trait loci analysis of seed coat color components for selective breeding in chickpea (Cicer arietinumL.). Can. J. Plant Sci. 91: 49-55. Chickpea (Cicer arietinum L.) is an annual grain legume, grown worldwide for human consumption with the potential to attract premium prices in markets such as India, Bangladesh and southern Asia. The ability to accurately select for seed coat color, an important export quality trait, would greatly benefit chickpea breeding programs. In order to determine the major genomic loci governing the color trait, the color components of CIE L* (luminance), CIE a* (red/green color) and CIE b* (blue/yellow color), C* (chroma or saturation of the color) and h° (hue or purity of the color) were mapped, and associated molecular markers were identified. A linkage map was constructed with 80 SSR markers distributed over 10 linkage groups at an average marker density of 2.8 cM. Two major quantitative trait loci (QTL), which accounted for up to 36 and 49% of the genetic variance and several smaller genetic effects were determined to govern the color components. These were consistent across two differing environments. Once validated, the markers that are close to and flanking these QTL and significantly associated with the minor gene effects will be useful in future color selective breeding programs.

Li, C.-Y., Li, W.-H., Lee, B., Laroche, A., Cao, L.-P. and Lu, Z.-X. 2011. Morphological characterization of triticale starch granules during endosperm development and seed germination. Can. J. Plant Sci. 91: 57-67. The morphology of starch granules and its changes during endosperm development and seed germination in triticale has been investigated under scanning electron microscopy (SEM). Starch granules were rapidly accumulating in triticale endosperm after 6 d postanthesis (DPA). The double-disk structure of starch granules was detected in endosperms from 6 DPA until 27 DPA in triticale and its parental crops, wheat and rye. The equatorial grooves of triticale starch granules were more susceptible to enzymatic hydrolysis than the broad or flat surfaces. Triticale starch was slowly degraded within 4 or 5 d post germination (DPG) and most starch granules were almost completely hydrolyzed after 9 DPG. Morphological changes of starch granules observed under SEM during the in vitro enzymatic hydrolysis were consistent with patterns identified during the germination process. As a hybrid of wheat and rye, triticale inherits many morphological characteristics of starch synthesis and storage in the seed endosperm. However, triticale also possesses unique features of granule shape, size, distribution, and enzyme susceptibility. These results will make it possible to effectively utilize triticale starch in the starch-based production.

Buckley, K. E., Mohr, R. M. and Therrien, M. C. 2011. Agronomic performance of barley cultivars in response to varying rates of swine slurry. Can. J. Plant Sci. 91: 69-79. Selection of crop variety may address concerns of potential adverse effects of preplant manure slurry application on crop yield and quality due to nutrient availability and lack of precision in application rate. An experiment was conducted in two field locations in southern Manitoba to assess the impact of slurry rate on growth, yield and quality of three barley (Hordeum vulgare L.) cultivars (Harrington, Rosser, Stander). Treatments included three rates of swine slurry, an unfertilized check and an inorganic fertilizer treatment at the recommended N rate based on preseeding soil nutrient tests. While the current study demonstrated no significant difference in the grain yield response of barley cultivars to rates of slurry application, higher rates of swine slurry may have a negative effect on milling quality (percentage of plump kernels) depending on cultivar, but had little effect on other quality parameters such as test weight and 1000-kernel weight. The absence of cultivar×slurry interaction for grain and biomass yield at each field location in each year indicated that all cultivars responded similarly to increasing rates of manure slurry for these traits. Grain protein concentration for all cultivars was unaffected by slurry amendment except at the highest application rate.

Lu, X-p., Yun, J-f., Gao, C-p. and Acharya, S. 2011. Quantitative trait loci analysis of economically important traits in Sorghum bicolor×S. sudanense hybrid. Can. J. Plant Sci. 91: 81-90. Many agronomic traits of Sorghum bicolor×S. sudanense hybrid are quantitatively inherited, and the gene mapping of these traits has important research and practical consequences. In this study, genetic mapping and quantitative trait loci (QTL) analyses were conducted using 248 F_2:3 plants of a cross between sorghum 314A (female parent) and Sudan grass 2002GZ-1 (male parent). A total of 178 markers (170 amplified fragment length polymorphism and 8 random amplified polymorphic DNA) were employed to construct a linkage map with 10 linkage groups covering 836 cM of the genome. The two parents expressed polymorphism for 10 agronomic characters (plant height, stem diameter, leaf number, leaf length, leaf width, spike length, tiller number, ratio of stem and leaf weight, fresh plant weight and dry plant weight). When analyzed for possible QTLs a total of 98 QTLs were identified in two test sites, out of which 26 QTLs overlapped in both sites. The average number of QTLs per character was found to be 2.6 and the distributions of these QTLs were found to be uneven across linkage groups. This, and the fact that molecular marker densities were not proportional with QTL frequencies, indicates that the detectable QTLs correlated with the agronomic traits and the genetic map can be useful for improvement in relevant characters in Sorghum bicolor×S. sudanense hybrids.

Lafrenière, C. and Drapeau, R. 2011. Seeding patterns and companion grasses affect total forage yield and components of binary red clover-grass mixtures. Can. J. Plant Sci. 91: 91-97. Red clover (Trifolium pratense L.) is the most popular seeded legume for forage production in northern Quebec and Ontario because of the poorly drained soils that prevail in these regions. The objective of this experiment was to determine which seeding patterns [mixed within a row (MR), single alternate rows (1 1), or double alternate rows (2 2)] and which companion grasses (smooth bromegrass, Bromus inermis L.; tall fescue, Festuca arundinacea Schreb.; orchardgrass, Dactylis glomerata L.; or timothy, Phleum pratense L.), in association with red clover, were best for sustaining the total forage yield of a red clover-grass mixture and how these factors affect red clover and grass components. Test plots were established at Kapuskasing, ON, and Normandin, QC. At each site, two independent seedings were performed and harvested over 3 yr following the seeding year. Total dry matter (DM) yield and contribution of red clover grasses and weeds to total forage yield were measured. The MR pattern gave higher yield over both alternate seeding patterns by nearly 0.5 Mg DM ha^-1 at the Normandin site and 1.0 Mg DM ha^-1 at the Kapuskasing site. Neither the seeding pattern nor the companion grass species improved significantly the contribution of red clover to total forage yield beyond the second production year even though there were differences between sites. Environmental conditions, principally high precipitation in the fall, and maturity stage at harvest resulted in major differences between sites. Results from this experiment showed that tall fescue and orchardgrass could be good alternatives to timothy or bromegrass in association with red clover given that plots were still productive in the third production year and invasion by weeds was lower.

Acharya, S. N., Acharya, K., Paul, S. and Basu S. K. 2011. Antioxidant and antileukemic properties of selected fenugreek (Trigonella foenum-graecum L.) genotypes grown in western Canada. Can. J. Plant Sci. 91: 99-105. Fenugreek (Trigonella foenum-graecum L.) is an annual forage legume known to have a number of important medicinal properties such as being anti-diabetic and hyperchloesterolaemic among others. In this study we have investigated the anti-oxidant and antileukemic properties of five fenugreek genotypes (L3068, L3375, Tristar, PI143504 and Amber) grown in western Canada for their potential use as nutraceuticals. Our preliminary experiments conducted in two different laboratories showed that the seeds grown in western Canada have anti-oxidant and antileukemic properties and the genotypes differ in the two traits studied. All the genotypes were found to be good scavengers for hydroxyl and free radicals. Among all the varieties, L3068 showed a higher EC₅₀ value i.e., lower inhibitory activity for lipid peroxidation than the standard catechin. Although all five extracts showed significant antioxidant activity, the crude extract of Tristar was the most effective. Out of the five cultivars of fenugreek, Amber and L3375 showed a robust antileukemic activity followed by Tristar. Hence we conclude that Tristar has the best potential among all the genotypes tested to be used as a future nutraceutical crop when grown in western Canada.

Aguado-Santacruz, G. A., Betancourt-Guerra, D. A., Siquerios-Cendón, T., Arévalo-Gallegos, S., Rivera-Chavira, B. E., Nevarez-Moorillon, G. V., Moreno-Gómez, B. and Rascón-Cruz, Q. 2011. Comparison of the structure and organization of therrnaoperons of Bouteloua gracilisandZea mays. Can. J. Plant Sci. 91: 107-116. We studied the genomic structure of Bouteloua gracilis chloroplast DNA (cpDNA) and compared it with the sequenced ribosomal RNA spacer region from other cereals. This will allow us to understand chloroplast topology and the recombination ability of cpDNA. The development of potential tools for biotechnology applied to cereals can be focused through the study of cpDNA in family related grasses, such as B. gracilis. cpDNA was prepared from green B. gracilis and Zea mays plants using a modified NaCl method. A 2332 bp intergenic spacer (IGS) region (rrna16S-trnI-trnA-rrna23S) from B. gracilis was sequenced, which showed great similarity (at least 92%) to IGS region from Z. mays, Oryza sativa and Saccharum officinarum. A physical map constructed by Southern hybridization using petA, psbA, psbD, ndhA, rbcL, 16S and 23S rDNA digoxigenin-labelled probes showed low organizational resemblance to maize cpDNA. Moreover, when compared to a similar fragment of Z. mays, a 239 bp intron deletion was found in the trnI gene in the B. gracilis cpDNA. Restriction and hybridization analyses suggested that the B. gracilis cpDNA has a molecular weight of 130 Kb. We expect that the findings reported in this work can be a baseline for increasing our knowledge in chloroplast organization in grasses and for the development of molecular tools.

Bueckert, R. A. 2011. Simulated hail damage and yield reduction in lentil. Can. J. Plant Sci. 91: 117-124. The severity of crop damage by hail is frequently estimated using equations derived from controlled experiments, but this approach has not been extended to the indeterminate pulse crop lentil (Lens culinaris L.). The objective was to simulate hail damage on two lentil cultivars, and estimate yield reduction for use in the Crop Insurance Industry. Hail damage was simulated by controlled canopy crushing on two cultivars, CDC Blaze and CDC Sedley at 4 location-years in Saskatchewan in 2006 and 2007. Plots received simulated damage as the untreated control (0%), 30, 60 or 90% canopy height reduction by crushing at each of four growth stages: vegetative, early flowering, pod-filling, and physiological maturity. As damage intensity increased from 0 to 90%, yield decreased in both cultivars. Most yield reduction (>65%) was seen when damage occurred in reproductive growth. Yield reduction for lentil damaged in vegetative growth was described by linear models, and the reproductive stages by quadratic models. The equations will help improve hail damage assessment in lentil on the Northern Great Plains.

Goyal A., Beres, B. L., Randhawa, H. S., Navabi, A., Salmon, D. F. and Eudes, F. 2011. Yield stability analysis of broadly adaptive triticale germplasm in southern and central Alberta, Canada for industrial end-use suitability. Can. J. Plant Sci. 91: 125-135. Triticale (×Triticosecale Wittmack) is a cereal crop with high grain yield and biomass potential, which are traits desired in biorefinery processes that currently utilize wheat (Triticum aestivum). This study was conducted to evaluate the performance of introduced germplasm for its adaptability to selected Canadian prairie agroecosystems, and to benchmark both introduced and registered triticale lines against hard red spring wheat. To investigate the genotype×environment interaction effects on the performance of triticale genotypes, 30 genotypes (27 triticale; 3 hard red spring wheat) were grown in three environments for 3 yr (2005-2007) in southern and central Alberta, Canada. Variance due to genotypes, years, locations, and their interactions were studied by employing several stability analysis models. Site Regression Model (SREG) and GGE biplot analysis were conducted to rank the relative yield performance of cultivars and to identify stable genotypes. Triticale consistently produced higher grain and biomass than hard red spring wheat, but some lines were high in pentosan content, produced low test weight, and possessed unacceptable growing degree day requirements. However, several of the introduction lines displayed superior trait performance and high stability. Five advanced to “C” level registration testing with one subsequently recommended for registration. The results provide evidence that some of the global triticale germplasm are well-suited to the production environments of the Canadian prairies, and that triticale has potential to be the ideal cereal platform for future technological and biorefinery end-use applications.

Olson, M., Bandara, M., Bing, D. J., Kruger, A., Henriquez, B. and Bremer, E. 2011. Evaluation of mungbean accessions for the southern Canadian prairies. Can. J. Plant Sci. 91: 137-141. Mungbean [Vigna radiata (L.) Wilczek] accessions were screened under field conditions to determine their suitability for commercial production in regions similar to those used for dry bean production on the Canadian prairies. Field studies were conducted in 2007 and 2008 at two locations in southern Alberta and in 2007 at one location in southern Manitoba. Two mungbean lines produced a minimum of 400 kg seed ha^-1 at 4 of 5 site-years, even with as little as 2240 crop heat units (CHU). The best-yielding accession produced an average seed yield of 750 kg ha^-1. Although seed yields were low relative to dry bean (1920 to 3100 kg ha^-1), substantial increases could likely be obtained through improvements in cultural practice and cultivar development.

Stoklosa, A., Nandanavanam, R., Puczel, U. and Upadhyaya, M. K. 2011. Influence of isoxaflutole on colonization of corn (Zea mays L.) roots with arbuscular mycorrhizal fungus Glomus intraradices. Can. J. Plant Sci. 91: 143-145. In a greenhouse pot culture study, corn plants were grown in sterilized soil containing mycorrhizal fungus Glomus intraradices and different concentrations of Converge Pro® herbicide (19.8, 39.6, 79.2, and 158.4 µg a.i. isoxaflutole L^-1 soil). Mycorrhizal colonization of corn roots was observed to be 10 to 20% at 6 wk (exp. I) and 50 to 60% at 8 wk (exps. II and III) of plant growth. Isoxaflutole did not inhibit mycorrhizal colonization in any of the three experiments. These results show that the use of isoxaflutole does not affect corn plants by influencing mycorrhizal colonization for up to 8 wk of growth.

Debnath, S. C. 2011. Bioreactors and molecular analysis in berry crop micropropagation - A review. Can. J. Plant Sci. 91: 147-157. While berry fruits have long enjoyed huge popularity among consumers, tremendous progress in plant tissue culture, resulting in great advances in micropropagation, has occurred. Of particular significance has been the evolution of the technology permitting multiplication of berry plants in bioreactors containing liquid media. Although automation of micropropagation in bioreactors has been advanced as a possible way of reducing propagation cost, optimal plant production depends upon better understanding of physiological and biochemical responses of plant to the signals of culture microenvironment and an optimization of specific physical and chemical culture conditions to control the morphogenesis of berry plants in liquid culture systems. Clonal fidelity can be a serious problem, and molecular strategies have been developed in order to reduce the variation to manageable levels. Molecular markers have been introduced to tissue culture research and can potentially be used in various facets of pertinent studies with berry crops. The paper focuses on bioreactor systems combined with semi-solid media used for in vitro culture of berry crops, cultivation of micropropagules and employment of molecular markers in micropropagated plants for the assessment of genetic fidelity, uniformity, stability and trueness-to-type among donor plants and tissue culture regenerants. The pertinent literature is reviewed and the relative merits and shortcomings of the various molecular markers applied are presented with an emphasis on the nature of tissue culture-induced variation.

Yu, U., Zhao, Y.-Q., Zhao, B., Ren, S. and Guo, Y.-D. 2011. Influencing factors and structural characterization of hyperhydricity of in vitro regeneration in Brassica oleracea var. italica. Can. J. Plant Sci. 91: 159-165. This study examines factors that affect the occurrence of hyperhydric tissue in in vitro cultures of Brassica oleracea variety italica. The anatomy of normal and hyperhydric leaves of plantlets regenerated from the hypocotyls was compared using scanning electron microscopy and transmission electron microscopy. In hyperhydric leaves palisade tissue was absent and the spongy mesophyll displayed large, unorganized intercellular spaces. Hyperhydric leaves had abnormal stomata with deformed guard cells. Significant ultrastructural differences were observed between chloroplasts in normal and hyperhydric leaves. The effects of zeatin, indoleacetic acid, silver nitrate and sucrose on the formation of hyperhydric shoots were studied. Zeatin was the most important factor, followed by sucrose concentration, AgNO₃ and indoleacetic acid. The process of hyperhydricity was found to be reversed by increasing the agar concentration and eliminating NH₄NO₃ from the macro-elements in the MS medium. This is the first report of hyperhydricity in Brassica oleracea, and our study gives a better understanding of the factors that influence hyperhydricity during in vitro regeneration in Brassica crops.

Edwards, D., Ehret, D. and Jolliffe, P. 2011. Temporal variations of starch and mass in greenhouse tomato leaves under CO₂enrichment. Can. J. Plant Sci. 91: 167-177. A plant-based method of guiding CO₂ dosing may improve the effectiveness of CO₂ enrichment in commercial greenhouse tomato (Lycopersicon esculentum Mill) production. The temporal dynamics of two plant response indicators, leaf starch and leaf mass per unit area (LMA) were investigated in commercial and research greenhouses throughout day/night periods, as well as after the onset of CO₂ enrichment. Both leaf starch and LMA tended to follow the diurnal profile of light but with 3 to 4 h of lag. The magnitude of the response, especially for starch, was affected by leaf position, CO₂ enrichment and light. The highest starch contents were measured between 1400 and 1600 and the lowest levels occurred in the morning between sunrise and 1100. In many cases plants carried over substantial starch in upper leaves from one day to the next, indicating a carbon-surplus state. In the onset experiment leaf starch and LMA increased with 4 d of exposure to CO₂ enrichment for mid and upper canopy leaves and continued to increase to the end of the monitoring period (7 d). Leaf starch contents and LMA are indicators of plant carbon status that show potential for guiding CO₂ dosing.

Kappel, F., MacDonald, R. A., Brownlee, R. T. and McKenzie, D.-L. 2011 SPC103 (Sentennial™) sweet cherry. Can. J. Plant Sci. 91: 179-181. SPC103 (Sentennial™) is a sweet cherry (Prunus avium L.) that has been released by the Pacific Agri-Food Research Centre (PARC-Summerland), Agriculture and Agri-Food Canada at Summerland, BC, as part of the ongoing sweet cherry breeding program that began in 1936. Sentennial™ is the latest maturing cultivar released from PARC-Summerland and has very good fruit size and firmness. It was released to growers for advanced commercial testing in 2006. The name Sentennial™ was chosen in honour of the District of Summerland's centennial year in 2006 and it was spelled with an “S” to maintain the tradition of starting most cherry cultivar names from the Summerland breeding program with an “S”.

Hwang, S. F., Ahmed, H. U., Strelkov, S. E., Gossen, B. D., Turnbull, G. D., Peng, G. and Howard, R. J. 2011. Seedling age and inoculum density affect clubroot severity and seed yield in canola. Can. J. Plant Sci. 91: 183-190. Clubroot, caused by Plasmodiophora brassicae, is a serious threat to canola (Brassica napus,B. rapa) production in western Canada because of its long-lived resting spores, high spore production potential, and negative impact on seed yield when inoculum pressure is high. The effect of inoculum density was studied by diluting heavily infested field soil with pathogen-free soil-less potting mix at seven increments, ranging from completely pathogen-free to 100% infested soil, and also by incorporating resting spores into the soil-less mix at concentrations of 1×10⁵ to 1×10⁸ spores cm^-3, along with a non-inoculated control. Seed of the susceptible canola cultivar 34 SS 65 was planted in soil of each treatment, grown to maturity, and rated for plant height, seed yield, and clubroot severity (0-3 scale) at harvest. Clubroot severity increased and plant height and seed yield decreased with increasing inoculum density. To assess the effect of seedling age on reaction to clubroot, resting spores of P. brassicae were inoculated onto roots of 1-, 2-, 3- and 4-wk-old seedlings of 34 SS 65. In addition, seed (i.e., 0-wk-old seedlings) was sown into infested soil. Inoculation of young seedlings resulted in higher clubroot severity, shorter plants and lower yield than inoculation of older seedlings. These results indicate that seed treatment fungicides with a long residual period (4 wk or more) may be useful for the management of clubroot.

Zuo, S., Yin, Y., Zhang, L., Zhang, Y., Chen, Z., Gu, S., Zhu, L. and Pan, X. 2011. Effect and breeding potential of qSB-11^LE, a sheath blight resistance QTL from a susceptible rice cultivar. Can. J. Plant Sci. 91: 191-198. Sheath blight (SB) caused by Rhizoctonia solani is one of the most important diseases of rice worldwide. The QTL qSB-11^LE, located on chromosome 11 of an SB-susceptible Oryza japonica rice cultivar Lemont, was identified in previous studies. In this study, its effect on SB resistance and its potential in breeding programs were evaluated using a set of near-isogenic lines (NILs) that exhibit three different genotypes at the qSB-11^LE locus and seven backcross populations. Results of field disease evaluation under artificial inoculation showed that the inheritance of resistance of qSB-11^LE to SB is controlled by additive gene action and that the genes have a dosage effect on SB resistance. In greenhouse evaluations, the resistance effect of qSB-11^LE was expressed at 11 and 14 d after inoculation at the tillering stage. Analysis of field resistance of six BC₁F₁ populations and one BC₂F₁ population, developed from the backcrosses between Lemont as the donor parent and six commercial O. indica rice cultivars as recurrent parents, indicated that qSB-11^LE could be effectively used to enhance these cultivars' SB resistance. These observations suggest that the qSB-11^LE has considerable potential in rice breeding for resistance to SB, and that its flanking molecular markers could be employed in practical breeding programs for marker-assisted selection.

Feng, J., Hwang, R., Chang, K. F., Conner, R. L., Hwang, S. F., Strelkov, S. E., Gossen, B. D., McLaren, D. L. and Xue, A. G. 2011. Identification of microsatellite markers linked to quantitative trait loci controlling resistance to Fusarium root rot in field pea. Can. J. Plant Sci. 91: 199-204. Fusarium root rot, caused by Fusarium solani (Mart.) Sacc. f. sp. pisi (F. R. Jones) W. C. Snyder & H. N. Hans, is the most common root disease of field pea (Pisum sativum L.) in western Canada. In this study, a recombinant inbred line (RIL) population (n=71) of field pea, derived from crosses between a resistant cultivar Carman, and a susceptible cultivar Reward, was evaluated to identify quantitative trait loci (QTL) controlling resistance to Fusarium root rot. The parental genotypes and RILs were evaluated for resistance to root rot following inoculation with F. solani in field experiments during 2007 and 2008. The frequency distribution of disease severities among the RILs was continuous. Transgressive segregation for resistance was observed among the RILs, with five lines more resistant than Carman, but no lines were more susceptible than Reward. To identify DNA markers linked with the resistance, 213 microsatellite markers were screened with genomic DNA from the two parental cultivars. Only 14 markers were polymorphic between the two parents and were used to genotype each of the RILs. Quantitative trait loci analysis based on the mean disease severity data from 2007 and 2008 identified a QTL that explained 39.0% of the phenotypic variance in the RIL population. This QTL is flanked by markers AA416 and AB60 on linkage group VII. The microsatellite markers that are closely linked to this QTL may be useful for marker assisted selection to develop cultivars with superior Fusarium root rot resistance.

Darbyshire, S. J., Francis, A., Crompton, C. W. and Swanton, C. J. 2011. The Biology of Canadian Weeds. 145. Muhlenbergia frondosa (Poir.) Fernald. Can. J. Plant Sci. 91: 205-219. Muhlenbergia frondosa is a perennial grass native to eastern North America, which naturally inhabits moist to wet forest margins and openings, freshwater littoral habitats, and grasslands. In Canada, its spread as a weed appears to have coincided with changes in cultivation practices during the past few decades. Infestations in such crops as maize and soya bean have been reported mainly from southern Ontario and Quebec, and the Midwest and northeastern areas of the United States, where it reduces yields and can be difficult to control. It is shade tolerant and able to compete under the closed canopy of crops. Although this weed can be controlled by herbicides, its ability to spread by regrowth from rhizomes, and its abundant seed production, cause ongoing problems in arable fields, particularly in conservation-tillage systems. As a warm-season C₄ grass, growth begins relatively late in the season (early June in Canada), after most intensive weed control measures have already been taken. Timing herbicide application with active growth stages (10-30 cm) is most effective and the use of herbicide-tolerant crops provides additional control opportunities after crop planting.

Qi, Z.-m., Sun Y.-n., Wu, Q., Liu, C.-y., Hu, G.-h. and Chen, Q.-s. 2011. A meta-analysis of seed protein concentration QTL in soybean. Can. J. Plant Sci. 91: 221-230. An integrated map of QTLs related to seed protein concentration in soybean has been constructed, based on the public genetic map, soymap2 as a reference map, along with a set of 107 QTLs reported in the literature over the past 20 yr. Each of these QTLs was projected onto the soymap2 by software package BioMercator v2.1. Twenty-three consensus QTLs were detected. The confidence interval at all sites ranged from 1.52 to 14.31cM, and the proportion of the phenotypic variance associated with each of them from 1.5 to 20.8%. Major chromosomal sites were identified on LG I (Gm20), four important sites were identified, involving LG A1 (Gm05), B2 (Gm14), E (Gm07) and M (Gm15). A meta-analysis approach was used to improve the precision of the location of these sites. These results facilitate gene mining and molecular assist-selection in soybean.