Canola Cultivars Research Articles

Seed weight in canola as a function of assimilate supply and source-sink ratio during seed filling period

Understanding variation in SW (seed weigh) is of major importance in understanding SY (seed yield) variation. The objective of this study was to determine factors such as SN (seed number) per unit area, SFD (seed filling duration) and SFR (seed filling rate) and temperature, LAI (leaf area index), LAD (leaf area duration), above-ground dry matter, CGR (crop growth rate), leaf dry matter remobilization and efficiency and SSR (source-sink ratio) around SFP (seed filling period), affecting SW in canola (Brassica napus L.). The experiment was conducted at Agricultural Research Station of Gonbad, Iran, during 2005-7. Two cultivars of spring type canola (Hyola401 and RGS003) as subplots were grown at 5 sowing dates (SDs) as main plots, spaced approximately 30 days apart, to obtain a wide range of environmental conditions during SFP. The experiment was arranged in two conditions, i.e. supplemental irrigation (SI) and rainfed (RF). SW was influenced by the growing season rainfall and temperature. The availability of the crop to produce and to remobilize photosynthetic assimilates to developing seeds was a good determinant factor for SW. SW increased with increase in LAI, above-ground dry matter production and remobilization and SSR around SFP, leading to an increased SY, suggested that SW primarily depends on the resource availability. The relationships of SW with SFR and SFD and above-ground dry matter, LAI, leaf dry matter remobilization and efficiency and SSR around SFP, over environmental conditions, sowing dates and cultivars, showed these variables to be generally applicable in canola SW determination.

Efficacy of integrated fertilizer management to improve agronomic and physiological traits of canola cultivars

The effects of integrated chemical and organic fertilizers on quantitative, qualitative and physiological traits of two canola cultivars were studied in East Azerbaijan Research Center for Agriculture and Natural Resources, Iran, during 2011 and 2012 growing seasons. The first factor comprised six levels of fertilizers including organic, chemical, and their combination and the second factor was two canola cultivars. Fertilizer treatments had significant effect on all studied traits except for proline, oil percentage, oleic acid, linolenic acid, seed sulfur, and potassium content in the first year, and leaf area, protein percentage, 1000 seed weight, seed number in silique, silique number in plants, oleic acid, and linolenic acid in the second year. Canola response to fertilizer proportions was quite different so that in the first year chemical fertilizations were better, while in the second year the effect of organic fertilizations was more pronounced. High level of organic fertilizer improved nitrate reductase activity, photosynthesis, chlorophyll content, and final seed yield in the second year. It seems that the positive effect of cattle manure would be visible at least 1 year after application. Moreover, canola cultivars differed from each other in terms of some agronomic and physiological traits during each year of the experiment.

Triacontanol modulates photosynthesis and osmoprotectants in canola (Brassica napus L.) under saline stress

An experiment was conducted to assess the effect of pre-sowing seed treatment with triacontanol (TRIA) in canola (Brassica napus L.) cultivar (RBN-3060) under saline stress. Canola seeds were soaked in three levels of TRIA (0, 0.5, and 1 mg L−1) for 12 hours. Three levels of salt stress (0, 100, and 150 mM NaCl) in full strength Hoagland's nutrient solution were applied to 56-days-old plants. Salt stress caused a significant reduction in growth, gas exchange, photochemical quenching (qP), and shoot and root K+ contents, while increased leaf glycine betaine, free proline, and shoot Na+ contents. Pre-sowing seed treatment with TRIA increased shoot fresh weight, number of seeds per plant, photosynthetic rate, transpiration rate, ratio of chlorophyll a/b, qP, electron transport rate, shoot and root K+ contents, and free proline and glycine betaine contents of canola plants at various TRIA levels under nonsaline or saline conditions.

Development of High-throughput Molecular Markers for Blackleg (Leptosphaeria maculans) Resistance Genes in Brassica napus for Gene Stacking

Quinta' and 'Glacier' are two important winter type canola cultivars from Europe. 'Quinta' has two independent blackleg resistance gene loci, Rlm1 and Rlm4; 'Glacier' has two other genes, Rlm2 and Rlm3. This study focuses on mapping the resistance genes Rlm1 and Rlm3 using high throughput SRAP (sequence related amplified polymorphism) markers and SNPs. The F2 and F3 populations were constructed with crosses of 'Westar' × 'Quinta' and 'Westar' × 'Glacier'. The populations were screened with the corresponding isolates. The phenotype segregation in the populations supported that a single dominant resistance gene controls the resistance in 'Quinta' and Glacier separately. The closest SRAP marker was identified for the resistance gene in 'Quinta' by using 256 pairs of primers and screening 2,500 polymorphic loci. B342 is 1.5 cM to Rlm1 and 6.8 cM to Rlm3. SNP80870 developed from the N7 orthologous region in Arabidopsis was 3 cM to Rlm3. A population for stacking the three resistance genes (Rlm1, Rlm3 and LepR3) was constructed. Marker screening and disease inoculation were both used for the selection of lines with the three resistance genes.

Crop and livestock production for dual-purpose winter canola (Brassica napus) in the high-rainfall zone of south-eastern Australia

Dual-purpose use of canola (Brassica napus) for forage in winter before seed production is a practice recently developed in southern Australia. The feasibility for dual-purpose spring canola (B. napus annua) in the medium-rainfall zone (450–650mm) has been demonstrated commercially, with significant adoption. Testing of later-maturing, dual-purpose winter canola (B. napus biennis) in long-season, high-rainfall areas (>650mm) has been restricted to mechanical defoliation or crash grazing. We conducted a series of six field experiments to evaluate the crop and livestock productivity of dual-purpose winter canola, involving a variety of stocking rates, grazing regimens and different cultivars at Canberra, ACT, and Young, NSW, in south-eastern Australia in 2007 and 2008. European winter canola cultivars sown between 21 March and 21 April provided 800–1100 dry sheep equivalent (DSE) grazing days/ha in Canberra and 1550–2600 DSE grazing days/ha in Young with little impact on subsequent yield (range 2.6–5.8t/ha), provided the sheep were removed from crops prior to bud elongation. Grazing occurred between 18 June and 1 September in Canberra and between 16 June and 14 August in Young and generally had no effect on harvest index or oil content. High stocking rates for short duration (126DSE/ha for 7 days) reduced sheep live-weight gains and meat production by ∼50% (110g/day; 92kg/ha) compared with stocking rates of low (22DSE/ha for 47 days) or moderate (43DSE/ha for 22 days) stocking rates (mean 220g/day; 182kg/ha) despite similar overall grazing pressure (882–1034 DSE grazing days/ha). The flexibility in sowing date and grazing times afforded by the vernalisation characteristics of winter canola make it an ideal, flexible option in high-rainfall mixed-farming systems. Winter canola could complement or even replace the traditional later-sown spring cultivars (for dual-purpose and/or grain-only production) in areas with high rainfall (>650mm) where early sowing opportunities (March) and cooler spring temperatures can maximise yield. Our results demonstrate significant potential for high livestock production and high grain and oil yield from dual-purpose winter canola in high-rainfall environments.

Effect of nitrogen rate on seed yield, protein and oil content of two canola (Brassica napus L.) cultivars

A field experiment was conducted at Rice Research Station, Tonekabon, Iran, to determine the effect of N rate on seed yield, protein and oil content of two canola (Brassica napus L.) cultivars. Two canola cultivars (‘Hayola-308’ and ‘RGS-003’) and five N rates (0, 50, 100, 150, and 200 kg ha­-1), organized into a randomized complete block design with a factorial treatment arrangement and three blocks, were applied to plot areas. Results showed that N rate effect was significant (P < 0.01) for seed yield, protein content and yield, and oil yield but not for oil content. On the other hand, cultivar had only significant (P < 0.01) effect on seed protein and oil content. Moreover, the interaction between N rate and cultivar was significant at P < 0.01 for seed, protein and oil yield, illustrating that cultivars showed different responses to N rates for these traits. In general, the quadratic equation provided a good description of the relationship between seed, protein and oil yield and nitrogen rate. For ‘Hayola-308’, seed, protein and oil yield increased significantly as N application rate increased from 0 to 150 kg ha-1, but thereafter remained constant. In contrast, for ‘RGS-003’, seed, protein and oil yield increased significantly as N application rate increased from 0 to 200 kg ha-1. Therefore, at the highest N application rate (200 kg ha-1), ‘RGS-003’ produced greater seed, protein and oil yield than ‘Hayola-308’. Averaged across N application rate, the seed protein content of RGS-003 was significantly (P < 0.01) higher than that of ‘Hayola-308’, while the opposite result was observed for seed oil content. This study demonstrated the differential response of two canola cultivars to N rate in terms of seed, protein and oil yield.

Response of herbicide-tolerant canola (Brassica napus L.) cultivars to four row spacings and three seeding rates in a no-till production system

Kutcher, H. R., Turkington, T. K., Clayton, G. W. and Harker, K. N. 2013. Response of herbicide-tolerant canola ( Brassica napus L.) cultivars to four row spacings and three seeding rates in a no-till production system. Can. J. Plant Sci. 93: 1229–1236. Appropriate management practices are important to reduce input costs and to optimize yield and crop quality. The objective of this study was to determine the optimum row spacing (23, 31, 46 and 61 cm) and seeding rate (3.2, 6.4 and 9.6 kg ha−1, or 87, 173 and 260 seeds planted m−2) for two herbicide-tolerant canola (Brassica napus L.) cultivars (an open-pollinated and a hybrid) under a no-till production system. Plant density and yield varied with row spacing, with the effect being linear in both cases. Plant density decreased with wider row spacing, from 112 plants m−2 at the 23-cm row spacing to 83 plants m−2 at the 61-cm row spacing. Yield decreased with wider row spacing, from 2397 kg ha−1 at the 23-cm row spacing to 2138 kg ha−1 at the 61-cm row spacing. Results from this study indicate that herbicide-tolerant cultivars of canola grown in no-till production systems under conditions of adequate soil fertility, effective weed management, minimal disease pressure, and good flea beetle control, produced the highest plant densities and yields at row spacing of 24–31 cm, that seeding rates in the range of 3.2–9.6 kg ha−1 had no effects on yield, and that a hybrid cultivar performed better than open-pollinated cultivars in terms of plant density, earliness and duration of flowering, and seed size. The study helps to better define the response of plant density and seed yield in herbicide-tolerant canola cultivars to changes in row spacing and seeding rate. In particular, the results of this study suggest that plant density may not be a reliable predictor of canola yield, although row spacing is an important consideration.

Population fluctuations of cabbage aphid, Brevicoryne brassicae (L.) (Hom.: Aphididae) and its natural parasitism rate on different canola cultivars

The cabbage aphid, Brevicoryne brassicae is one of the most destructive pests in Cruciferaceae or Brassicaceae plant family around the world. According to this pest rapid resistance to insecticide, using the resistant cultivars should be evaluated. In the present study, the different canola cultivars resistance against the cabbage aphid and the population fluctuations in canola fields and also the natural parasitism are evaluated in Shahre-rey region. To evaluate the population fluctuations and its natural parasitism on the RGS003, SLMOO46, Karag2, Licord, Sarigol, Opera, Ocapi and Talaei canola cultivars were cultivated in four replications using the complete randomised block design. The population fluctuations studies showed that the pest is active during the canola growth period in studied region, but the peak of population and damage is found in 6 May month. The results showed that natural parasitism percentage of cabbage aphid on different canola cultivars has not significant difference, but the parasitism amount in different sampling dates was significantly different, so that the natural parasitism maximum observed in date 29 April. These results showed that the different canola cultivars have significant effects on cabbage aphid and parasitoids activity amount. Using the present results, the recognised cultivars in integrated pest management programmes can be used to grow the laboratory aphids as the parasitoids hosts.

Evaluation of Camelina sativa (L.) Crantz meal as an alternative protein source in ruminant rations

Camelina sativa (CS) is an oilseed crop used for biofuel production. By-products from oil extraction are high in protein and can be used in ruminant rations; more information about their nutritive value is required also considering the antinutrional factor content of the by-products. The aim of this study was to evaluate the nutritive value of CS meal genotypes in comparison with canola. Ten CS genotypes and one canola cultivar were evaluated. Meals were obtained from seeds after solvent oil extraction. CS average crude protein (CP) content (g kg⁻¹ dry matter) was 457. Numerical differences in lysine and sulfur amino acid content were observed among CS genotypes. Glucosinolate (mmol kg⁻¹) content was higher for CS (23.1) than canola (7.2). Sinapine content (g kg⁻¹) was lower for CS (2.79) than for canola (4.32). Differences were observed among CS genotypes for rumen undegraded protein (RUP). Average RUP (g kg⁻¹ CP) was 316 for CS and 275 for canola. CS meal has potential for use in ruminant rations as a high-quality protein source. In vivo studies are needed to compare CS with other protein sources used in cattle rations. Implementation of breeding programs for improved meal quality is recommend.

Genetic diversity among some canola cultivars as revealed by RAPD, SSR and AFLP analyses.

To assess the genetic diversity among four canola cultivars (namely, Serw-3, Serw-4, Misser L-16 and Semu 249), random amplified polymorphic DNA (RAPD), simple sequence repeat polymorphism (SSR) and amplified fragment length polymorphism (AFLP) analyses were performed. The data indicated that all of the three molecular markers gave different levels of polymorphism. A total of 118, 31 and 338 markers that show 61, 67.7 and 81 % polymorphism percentages were resulted from the RAPD, SSR and AFLP analyses, respectively. Based on the data obtained the three markers can be used to differentiate between the four canola cultivars. The genotype-specific markers were determined, 18 out of the 72 polymorphic RAPD markers generated were found to be genotype-specific (25 %). The highest number of RAPD specific markers was scored for Semu 249 (15 markers), while Serw-4 scored two markers. On the other hand, Serw-3 scored one marker. The cultivar Semu 249 scored the highest number of unique AFLP markers, giving 57 unique markers, followed by Misser L-16 which was characterized by 40 unique AFLP markers, then Serw-3 giving 31 unique markers. While Serw-4 was characterized by the lowest number producing 14 unique positive markers. The dendrogram built on the basis of combined data from RAPD, SSR and AFLP analysis represents the genetic distances among the four canola cultivars. Understanding the genetic variability among the current canola cultivars opens up a possibility for developing a molecular genetic map that will lead to the application of marker-assisted selection tools in genetic improvement of canola.

Relevance of reproductive correlates in response of diamondback moth (Lepidoptera: Plutellidae) to plant quality

To study the relationships between leaf nitrogen and the reproductive potential of diamondback moth, all reproductive parameters of this pest raised on two canola cultivars were evaluated. A standardized regression coefficient (<em>β</em>) was used as an index for nitrogen-reproduction relationship strength. The only difference between net fecundity rate and net fertility rate is <em>h<sub>x</sub></em>’s effect, but the difference in their standardized regression coefficients was not significant [<em>β</em>=+0.934 (R<sup>2</sup>=0.87, F<sub>1,4</sub>=27.34, P=0.006) and <em>β</em>=+0.922 (R<sup>2</sup>=0.85, F<sub>1,4</sub>=22.825, P=0.009)]. Accordingly, gross fecundity rate and gross fertility rate differ only in <em>h<sub>x</sub></em>’s effect, but the difference in standardized regression coefficients again was not significant [<em>β</em>=0.895 (R<sup>2</sup>=0.8, F<sub>1,4</sub>=16.159, P=0.016)-0.890 (R<sup>2</sup>=0.79, F<sub>1,4</sub>=15.266, P=0.017)=0.005]. As gross fecundity rate differs from net fecundity rate only in midpoint survivorship (<em>L<sub>x</sub></em>)’s effect, it is understood that survivorship could affect the plant nitrogen–fecundity relation considerably (standardized coefficients difference=0.044) and could be a critical parameter in insectplant interactions. But, the terms of reproductive parameters, <em>i.e. L<sub>x</sub> </em>and <em>h<sub>x</sub></em>, showed the same effect on the strength of nitrogen-fecundity regression statistically, even though <em>L<sub>x</sub></em> has been selected frequently by many researchers as an important fitness correlate. Measuring the hatch rate could be recommended in trophic interactions studies due to its being easier to apply, more robust, and quicker to accomplish than measurement of survivorship; however, it is important as an indicator in combination with brood size for determining the initial population size of an insect herbivore.

First Report of Leptosphaeria biglobosa as a Stem Canker Pathogen of Brassicas in New Zealand.

Phoma black leg or stem canker, caused by Leptosphaeria maculans or L. biglobosa, is an important disease of brassicas, causing significant crop losses in areas such as Europe, Australia, and North America (1). Samples collected in 2011 from canola and forage brassica (swede, kale, and turnip) crops in the main New Zealand growing regions (Southland, Central Otago, Canterbury, Hawkes Bay, and Manawatu) to identify the causal agent(s) of the characteristic stem cankers, found many isolates of L. maculans, which has been reported previously in New Zealand (2), and three isolates identified by colony characteristics as L. biglobosa. Of the latter, two isolates were from canola (Brassica napus) stem cankers from Darfield and Lincoln, Canterbury, and one was from a kale (B. oleracea) stem canker from Lincoln. An isolate (ICMP10665) of similar morphology, from the International Collection of Microorganisms from Plants (ICMP), obtained from a basal rot lesion on a cauliflower (B. oleracea var. botrytis) plant in Levin, New Zealand in 1979, was also evaluated. The initial, incorrect identification of the latter isolate as L. maculans predates the reclassification of L. maculans group B isolates as a new species, L. biglobosa (1). These four isolates produced fluffy white mycelium and a yellow pigment on potato dextrose agar (PDA) after 5 days' growth, and abundant black-brown, globose pycnidia containing cylindrical hyaline conidia after 7 days. In contrast, L. maculans isolates had slower growth and no pigment production (4). Amplification of genomic DNA using species-specific primers LmacR, LmacF, and LbigF (1) generated a PCR product of 444 bp that is typical of L. biglobosa isolates. Sequencing of the PCR product from each of the four isolates showed they were 100% identical to a sequence of L. biglobosa 'brassicae' in GenBank (JF740198). To confirm the species identity of the isolates, the rDNA, actin, and β-tubulin gene regions were amplified (1,3). Sequences for the rDNA (568 bp), actin (941 bp), and β-tubulin (410 bp) gene regions were 99% identical to sequences of the same regions of isolates in GenBank for L. biglobosa 'brassicae' (AY48997, AY748949.1, and AY748997.1, respectively). The four L. biglobosa isolates were tested for pathogenicity on a canola cultivar commonly grown in New Zealand (Flash). Cotyledons of 10-day-old seedlings (n = 12 seedlings/isolate or control treatment) grown in a potting mix in pots were pricked with a sewing needle, and each wound inoculated with 10 μl of the appropriate conidial suspension (106 conidia/ml) or 10 μl sterilized distilled water for the control treatment. Leaf lesions that developed on the inoculated cotyledons were characteristic of those caused by L. biglobosa, i.e., small and dark with a distinct margin. No pycnidia were produced on the lesions. No lesions developed on the cotyledons of the non-inoculated control plants. The causal agents were confirmed as L. biglobosa by the colony morphology of isolates that grew from surface-sterilized, inoculated leaf lesions plated on PDA amended with 100 μg/ml ampicillin. The fungus was not isolated from control leaf tissue. To our knowledge, this is the first report of L. biglobosa as a pathogen of canola and kale in New Zealand. This finding shows that both causal agents of black leg are present in New Zealand's brassica cropping areas.

Seven fish oil substitutes over a rainbow trout grow-out cycle: II) Effects on final eating quality and a tentative estimation of feed-related production costs

The effects of seven alternative oils on final product quality and production cost were assessed in rainbow trout (Oncorhynchus mykiss). The tested oils were as follows: monola (a high oleic acid canola cultivar; MO), canola (rapeseed; CO), poultry by-product (chicken fat; PbPO), palm (PO), sunflower (SFO), high oleic acid sunflower (HOSFO) and soybean (SBO). Tested oils were included at a 75% substitution level of fish oil and were compared with a control diet containing 100% fish oil (FO). Fillets of trout fed FO contained a 2.8-fold higher amount of EPA + DHA in comparison with fish fed the alternative oils, whilst the n-6/n-3 ratios varied from 0.2 in FO to 3.67 in SFO. Fillet pigmentation was highly affected by the different dietary treatments, as was the refrigerated product shelf-life. Fillets of trout fed FO recorded significantly higher lipid peroxidation at days 6 and 9 of refrigeration compared with the other treatments. The fillet flavour volatile compounds were significantly affected by the treatments, but no differences were detected by the panellists in the sensorial analysis. A discrepancy between production costs at ‘feed mill’ or ‘on-farm’ was recorded, suggesting that FO replacement may result in no real economic benefit.

Sclerotinia sclerotiorum Populations Infecting Canola from China and the United States Are Genetically and Phenotypically Distinct

Genetic and phenotypic diversity and population differentiation of Sclerotinia sclerotiorum isolates infecting canola from China and the United States were investigated. Genetic diversity was assessed with eight microsatellite markers and mycelial compatibility groups (MCGs). Phenotypic diversity was assessed with sensitivity to three fungicides, production of oxalate and sclerotia, growth rate, and virulence on two canola cultivars. No shared MCGs or multilocus haplotypes were detected between the two populations, and populations differed significantly (P < 0.001). Recombination was detected in both populations but was greater in the Chinese population. A polymerase chain reaction detection assay showed that ~60% of the isolates were inversion-plus at the mating type locus. The two populations differed significantly (P < 0.05) for all of the phenotypic traits except for sensitivity to fungicide fluazinam and virulence. Isolates in the Chinese population were unique in several aspects. Despite the phenotypic differentiation, heritabilities of the phenotypic traits were similar for both populations. Significant correlations were found among five phenotypic traits. Cross resistance to benomyl and iprodione was detected. Virulence was not significantly correlated with any other phenotypic trait and had the least heritability. However, both populations were equally virulent on either a susceptible or a moderately resistant canola cultivars.

Sulphur application improves the growth, seed yield and oil quality of canola

Sulphur (S) nutrition is very important for harvesting potential seed and oil yield of rapeseed. This study evaluated response of foliage applied thiourea on the performance of two canola cultivars Shiralee and Dunkeld. Sulphur was applied to soil (40 kg ha−1) or foliage (500 and 1,000 mg L−1) at rosette, bud initiation and flowering stages using elemental S or thiourea as source, respectively; no S application was taken as control. Among all the treatments, soil application of S improved the crop growth, yield and oil quality in both cultivars and was followed by foliar application of thiourea at 1,000 mg L−1 compared with no application. Soil applied S and foliar thiourea (1,000 mg L−1) delayed the flowering and maturity. Soil and foliar applied S significantly improved leaf area index, crop growth rate, net assimilation rate and chlorophyll contents. Plant height, number of branches, siliqua per plant, seed number per siliqua, 1,000-seed weight, biological and seed yield were also increased by soil applied S and foliage applied thiourea (1,000 mg L−1). Nonetheless, improvement in harvest index, seed oil, protein and glucosinolate contents was only observed from foliage applied thiourea (1,000 mg L−1). Response of cv. Shiralee to sulphur application was better than cv. Dunkeld. In conclusion, foliar applied thiourea (1,000 mg L−1) can have potential to improve growth, yield and oil quality in canola and can be economically viable and attractive alternative source.

Cytology of infection, development and expression of resistance to Plasmodiophora brassicae in canola

AbstractThe timing and expression of resistance to four isolates of Plasmodiophora brassicae, collected from research sites where pathotypes 2, 3, 5 and 6 (Williams' system) had been dominant when characterised in 2006, were assessed in four new commercial cultivars of canola (Brassica napus) with resistance to clubroot. Each of the resistant cultivars was highly resistant to all four of the isolates, and there was no difference in their response to infection. Root hair infection occurred at high levels, but pathogen development occurred more slowly than in a susceptible cultivar (control). Secondary infection and development in cortical cells was severely inhibited in each of the resistant cultivars; only a few bi‐nucleated plasmodia were observed at 12 days after inoculation (DAI), and plasmodia were rarely observed at 18 and 24 DAI. In contrast, development in the susceptible cultivar had progressed to resting spores by 24 DAI. A dense ring of accumulated reactive oxygen species (ROS) was observed in the endodermis, pericycle and vascular cambium of non‐inoculated controls and inoculated plants of the resistant cultivars. However, the ROS ring disappeared rapidly in infected plants of the susceptible cultivar. Plasmodia invaded the stele of susceptible roots by preferentially colonising the xylem parenchyma cells. Expansion and enlargement of lignified xylem cells was observed by 35 DAI. The absence of any specific points of ROS accumulation or lignification of epidermal or cortical cells in the resistant cultivars indicates that a hypersensitive response is not the main mechanism of resistance in these lines. The uniform response of these resistant cultivars to the four isolates of P. brassicae indicates that the resistance in each cultivar may be conditioned by a gene(s) from a single source that confers broad resistance, because most sources of resistance to P. brassicae are pathotype specific.

Review: Breeding spring canola (Brassica napusL.) by the use of exotic germplasm

Rahman, H. 2013. Review: Breeding spring canola ( Brassica napus L.) by the use of exotic germplasm. Can. J. Plant Sci. 93: 363–373. The need of broadening genetic diversity in spring canola (Brassica napus) breeding programs seems to be the general consensus among canola breeders and researchers. Diversity analysis by the use of molecular markers has identified several B. napus gene pools as well as allied Brassica species that are genetically distinct from spring canola B. napus; and these gene pools can be used for the improvement of this crop. Use of genetically diverse and un-adapted B. napus germplasm in the breeding of spring canola can be challenging, as introduction of several unwanted traits/alleles from exotic germplasm into spring canola occurs, and this would require repeated cycles of breeding for improvement. Similarly, use of allied species can be even more challenging due to the difficulties associated with interspecific hybrid production, sterility of hybrids, linkage drag, and the introduction of unwanted alleles. However, this can be compensated in the long-term perspective for the improvement of this crop. Some research efforts have been made in recent years to broaden allelic diversity in spring canola for the improvement of seed yield and other traits in open-pollinated and hybrid cultivars with promising results. Seed yield is a complex trait which is controlled by several gene loci with multiple alleles at these loci as well as interactions between loci and different alleles. This makes the identification of right allelic combinations an extremely challenging task. However, canola breeders have been able to make steady improvements in this crop in past decades based on the amount of allelic diversity present in existing breeding material. Introduction of favourable new alleles in breeding programs would allow breeders to create superior allelic combinations, enhancing the diversity in current breeding materials to further improve the crop. With the availability of the Brassica genome sequence, knowledge of sequence variation in specific genes and cost-effective high-throughput genotyping, it is expected that molecular plant breeding will play an important role in the breeding of canola cultivars. Discovery of favourable allele combinations in a short span of time is likely to be facilitated through the application of modern breeding tools.

Blackleg disease of canola mitigated by resistant cultivars and four-year crop rotations in western Canada

In western Canada, canola is traditionally grown in rotation once every 4 years to restrict losses due to pests. Recently, growers have begun to produce canola more intensively due to market opportunities and cultivar improvements. This study was initiated to investigate the consequences of more intensive production of canola in rotations, integrated with currently available disease management practices, including blackleg resistant cultivars and fungicides. A 4 replicate split-plot experiment was established at Scott and Melfort, Saskatchewan with canola rotation treatments ranging from yearly to every second, third or fourth season in combination with pea, wheat and flax using a blackleg resistant and a blackleg susceptible cultivar. Sub-plots were fungicide treatments for blackleg and sclerotinia stem rot diseases. Blackleg incidence and severity was increased in rotations comprising more than one canola crop every four years, regardless of cultivar, although the blackleg resistant cultivar was much less affected than the blackleg susceptible cultivar. The yield of the blackleg resistant canola cultivar was similar among rotations that included canola every 2, 3 and 4 years. Fungicide application was of limited value to maintain canola yield. The results suggest that canola cultivars with strong blackleg resistance can be grown more intensively than once every 4 years with limited yield reduction. However, the increased severity of infection and amount of infested residue produced as canola rotations are intensified, which occurs even with resistant cultivars, increases the risk of inoculum carry-over, resistance breakdown and yield loss. Therefore, it would be prudent for western Canadian canola growers to adhere to less intensive inclusion of canola in rotations, such as one canola crop in 4 years, as an effective blackleg management strategy.

Competitive ability of canola cultivars (Brassica napus L.) against their natural weed populations

To determine the competitive ability of canola cultivars against natural weed populations, a field experiment was conducted in northern Iran, Mazandaran province, during 2010–2011 growing season. The experiment was arranged as a factorial randomized complete block design with three replications. Factors were four canola cultivars (Hayola-420, Hayola-308, RGS-003 and PF) and two weed management regimes (weed-free condition and weedy condition). Averaged across weed management regimes, grain yield of RGS-003 was significantly higher than that of other canola cultivars. Weed interference significantly reduced canola grain yield and yield components, regardless of canola cultivar. The reduction in grain yield by weed competition was 15.5% for Hayola-308, 11.1% for RGS-003, 9.8% for PF and 6.6% for Hayola-420. This indicates that canola cultivar had different ability to withstand competition, which Hayola-420 had the highest (43.39) ability to withstand competition, followed by PF (40.28), RGS-003 (38.94) and Hayola-308 (34.54). The rank order of competitive ability of the canola cultivars was RGS-003 = Hayola-420 > PF = Hayola-308. Canola grain yield was positively (P < 0.01) correlated with silique number on main stem, grain number in silique of main stem, silique number on side branches, 1000 grain weight, and canola biomass, but negatively (P < 0.01) correlated with weed biomass, and not correlated with grain number in silique of side branches, plant height and harvest index. In conclusion, these results confirmed that there was a significant difference among canola cultivars for competitive ability against weeds.

Monola oil versus canola oil as a fish oil replacer in rainbow trout feeds: Effects on growth, fatty acid metabolism and final eating quality

Monola oil, a high oleic acid canola cultivar, and canola oil were evaluated as replacers of fish oil at three levels of inclusion (60%, 75% and 90%) in rainbow trout diets. After a 27-week grow-out cycle, the diet-induced effects on growth, fatty acid metabolism and final eating quality were assessed. Overall, no effects were noted for growth, feed utilisation or fish biometry, and the fatty acid composition of fish fillets mirrored that of the diets. Dietary treatments affected fillet lipid oxidation (free malondialdehyde), pigmentation and flavour volatile compounds, but only minor effects on sensorial attributes were detected. Ultimately, both oils were demonstrated to possess, to differing extents, suitable qualities to adequately replace fish oil from the perspective of fish performance and final product quality. However, further research is required to alleviate on-going issues associated with the loss of health promoting attributes (n-3 long chain polyunsaturated fatty acids) of final farmed products.