Nitrogen Recovery from Brassicaceae Oilseed Crops: A Function of Residue Quality

Blackshaw, R. E., Johnson, E. N., Gan, Y., May, W. E., McAndrew, D. W., Barthet, V., McDonald, T. and Wispinski, D. 2011. Alternative oilseed crops for biodiesel feedstock on the Canadian prairies. Can. J. Plant Sci. 91: 889–896. Increased demand for biodiesel feedstock has encouraged greater napus canola (Brassica napus L.) production, but there may be a need for greater production of other oilseed crops for this purpose. A multi-site field study was conducted to determine the oil yield potential of various crops relative to that of napus canola in the semi-arid, short-season environment of the Canadian prairies. Oilseed crops evaluated included rapa canola (Brassica rapa L.), juncea canola (Brassica juncea L.), Ethiopian mustard (Brassica carinata L.), oriental mustard (Brassica juncea L.), yellow mustard (Sinapis alba L.), camelina (Camelina sativa L.), flax (Linum usitatissimum L.), and soybean [Glycine max (L.) Max.]. Crop emergence and growth were generally good for all crops, but soybean did not fully mature at some locations. The number of site-years (out of a total of 9) that crops attained similar or greater yields compared to napus canola were camelina (6), oriental mustard (5), juncea canola (3), flax (3), soybean (3), rapa canola (2), yellow mustard (2), and Ethiopian mustard (1). The ranking of seed oil concentration was napus canola=rapa canola= juncea canola=flax>camelina=oriental mustard>Ethiopian mustard>yellow mustard>soybean. Considering yield and oil concentration, the alternative oilseed crops exhibiting the most potential for biodiesel feedstock were camelina, flax, rapa canola and oriental mustard. Oils of all crops were easily converted to biodiesel and quality analyses indicated that all crops would be suitable for biodiesel feedstock with the addition of antioxidants that are routinely utilized in biodiesel fuels.

Brassicaceae seed meals (BSMs) average 6% nitrogen (N) by weight and contain glucosinolates (GLSs) that produce biologically active compounds. A two-season field study was initiated to determine how Brassica juncea L., Brassica napus L., and Sinapis alba L. seed meals, each with different glucosinolate profiles, alter carrot ( Daucus carota L. subsp. sativus ) growth, microbial biomass N (MBN), and soil N mineralization. BSM applications of 1 and 2 t·ha −1 36 days before planting did not influence carrot emergence, whereas carrot emergence decreased up to 40% in S. alba treatments seeded 15 days after BSM application. Crop quality was unaffected by BSM treatments and total fresh market yields were equal to or higher than the unamended controls in both years. At 4 and 8 days after seed meal application, MBN in the high-GLS B. juncea and S. alba treatments was 48% to 67% lower than in the low-GLS B. napus treatment. Seasonal apparent net N mineralized expressed as a percentage of the total N applied in the seed meals was unaffected by glucosinolate concentration and ranged from 30% to 81% across both years. BSMs can be used to increase soil inorganic N and carrot yields, but crop phytotoxicity is possible depending on the meal and its respective glucosinolate content. GLS degradation products inhibit microbial N uptake in the short term, but longer-term N availability is not compromised.

The cabbage stem flea beetle (CSFB), Psylliodes chrysocephala L. (Coleoptera: Chrysomelidae), is one of the most important pests in European winter oilseed rape production. Adult beetles feed on young leaves whereas larvae mine within the petioles and stems. Larval infestation can cause significant crop damage. In this study, the host quality for CSFB of four oilseed rape (Brassica napus L.) cultivars and seven other brassicaceous species with different glucosinolate (GSL) profiles was assessed under controlled conditions. Larval instar weights and mortality were measured after 14 and 21 days of feeding in the petioles of test plants. To study the impact of GSL on the performance of larvae, the GSL contents in petioles from non‐infested and infested plants were analysed before, and 21 days after, the start of larval infestation. Larval performance was not significantly different between the four cultivars of oilseed rape, but differed considerably among the other brassicaceous species tested. In comparison to the weight of larvae in the standard B. napus cv. Robust, the larval weight was higher in turnip rape (Brassica rapa L. var. silvestris) and significantly reduced in white mustard (Sinapis alba L.), oil radish (Raphanus sativa L. var. oleiformis), and cabbage (Brassica oleracea L. convar. capitata var. alba). The duration of larval development increased in white mustard and oilseed radish. The GSL profiles of the petioles showed little difference between non‐infested and infested plants of oilseed rape whereas the content of aliphatic GSL increased in the infested turnip rape plants. In contrast, the aliphatic and benzenic GSL decreased in infested Indian rape (B. rapa subsp. dichotoma Roxb.). Larval weight was not correlated with the total GSL content of plants, neither before infestation nor 21 days after. Larval weight was positively correlated with progoitrin and 4‐hydroxyglucobrassicin. White mustard, which provides inferior host quality for larval development, has the potential to introduce insect resistance into high‐yielding oilseed rape cultivars in breeding programmes.

Plant establishment, yield and yield components of Brassicaceae oilseeds as potential biofuel feedstock

Variation und Vererbung von Glucosinolatgehalt und muster in Grünmasse und Samen von Raps (Brassica napus L.) und deren Zusammenhang zum Befall mit Rapsstängelschädlingen

Brassicaceae crops often produce an unexplained increase in plant-available soil N possibly related to bioactive compounds produced from glucosinolates present in the tissues. Our objective was to determine if glucosinolate-containing tissues inhibit nitrification, thereby potentially explaining this observation. Ammonium, NO(2)(-), and NO(3)(-) N were measured in soils amended with Brassicaceae ( Isatis tinctoria L., Brassica napus L., Brassica juncea L., and Sinapis alba L.) tissues containing different glucosinolate types and concentrations or Kentucky bluegrass ( Poa pratensis L.) residues with equivalent C/N ratios as the Brassicaceae samples. There was greater accumulation of NH(4)(+) N in soils amended with tissues containing high glucosinolate concentrations as compared to soils amended with tissues containing no or low glucosinolate concentrations. Nitrite N was detected only in soils amended with Brassicaceae tissues having the highest glucosinolate concentrations. The positive correlation of both NH(4)(+) and NO(2)(-) N accumulation with the glucosinolate concentration indicates the participation of glucosinolate hydrolysis products in nitrification inhibition.

Plants display a wide range of chemical defences that may differ in effectiveness against generalist and specialist insect herbivores. Host plant‐specific secondary chemicals such as glucosinolates (GS) in Brassicaceae typically reduce the performance of generalist herbivores, whereas specialists have adaptations to detoxify these compounds. The concentration of glucosinolates may also alter upon herbivory, allowing the plant to tailor its response to specifically affect the performance of the attacking herbivore. We studied the performance of three Lepidoptera species, two specialists [Pieris rapae L. (Pieridae), Plutella xylostella L. (Yponomeutidae)] and one generalist [Mamestra brassicae L. (Noctuidae)], when feeding on eight cultivars of Brassica oleracea L. and a native congener (Brassica nigra L.) and related this to the GS content. We tested the hypotheses (i) that a generalist herbivore is more affected by high GS concentrations, and (ii) that generalist feeding has a stronger effect on GS levels. Although performance of the three herbivores was different on the B. oleracea cultivars, M. brassicae and P. xylostella had a similar ranking order of performance on the eight cultivars. In most of the cultivars, the concentration of indole GS was significantly higher after feeding by P. rapae or M. brassicae than after P. xylostella feeding. As a consequence, the total concentration of GS in the cultivars showed a different ranking order for each herbivore species. The generalist M. brassicae performed equally well as the specialist P. xylostella on cultivars with high concentrations of GS. Our findings suggest that secondary metabolites other than GSs or differences in nutrient levels affect performance of the species studied.

Competitive crops or cultivars can be an important component of integrated weed management systems. A study was conducted from 2003 to 2006 at four sites across semiarid prairie ecoregions in Saskatchewan and Alberta to investigate the productivity and quality of canola (Brassica napusL.) and mustard cultivars under weed competition. Four open-pollinated canola cultivars, four hybrid canola cultivars, two canola-quality mustard and two oriental mustard cultivars [Brassica juncea (L.) Czern. & Coss.], and two yellow mustard (Sinapis alba L.) cultivars were grown under weedy and weed-free conditions. When combined across site-years, crop aboveground biomass at maturity and seed yield were reduced by weed interference, except for yellow and oriental mustard. However, seed oil and protein content of cultivars were not affected by weed competition. Among crop types, yellow and oriental mustard were best able to maintain biomass and seed yield under weed interference, followed in decreasing order of competitiveness by hybrid and open-pollinated canola, then canola-quality mustard. Key words: Brassica napus, Brassica juncea, Sinapis alba, weed competition

Oilseed rape is one of the most important oilseed crops of the world. Because of the success in quality breeding, the growing area of oilseed rape is gradually increasing. Although the seed quality is a very important breeding objective, the inheritance of the seed quality is not yet completely understood. It is often assumed, that most seed quality traits like oil, protein and glucosinolate (GSL) content are only determined by the maternal plant on which the seeds is grown and not influenced by the genotype of the pollinator. Therefore, the main objective of this study is to determine the effects of the pollen genotype on the important seed quality traits oil, protein, glucosinolate, tocopherol and sinapic acid content.Two separate experiments were conducted to meet this objective. In the first experiment ten pollen parents and two male sterile females (Falcon and Express) were used. For each pollen parent blocks with seven plots were grown containing three plots of the parent between two plots of each F1. Ten single plants of the two male sterile parents were transplanted into the center of the pollinator plots by hand before winter. The experiment was performed with two replications in a randomized complete block design at three locations (Goettingen, Einbeck, and Teendorf) in the season 2002/2003. The seed quality traits oil, protein and sinapic acid ester content were analysed by near-infrared reflectance spectroscopy (NIRS), glucosinolate and tocopherol contents were analysed by high performance liquid spectroscopy (HPLC), and the fatty acids were analysed by gas liquid chromatography (GLC).In the second experiment single F2 seeds from four crosses were analysed by NIRS for protein and glucosinolate content. In each cross four bulks were selected: high and low in protein and in glucosinolate, respectively. In the season 2002/2003 the four bulks from each cross were grown in a randomized complete block design with two replications in three locations (Goettingen, Einbeck, Teendorf). Six parental lines were also included in the experiment. The seed quality traits oil, protein and glucosinolate content were analysed by near-infrared reflectance spectroscopy (NIRS).In the first experiment, the results have revealed that highly significant correlations between pollen parents and F1s were observed for indole GSL, sinapoylglucose and total sinapic acid ester. In the analysis of variance, significant effects for pollen genotype were observed for oil, indole GSL, indole/aliphatic GSL, fatty acids, sinapoylglucose, γ-tocopherol and α/γ-tocopherol. In the second experiment the response to selection of F2 single seeds from individual plants was investigated. First reliable NIRS calibration equations for the single seeds were developed with a wide-range of oil, protein, and glucosinolate content. High correlations of R2 = 0.98, R2 = 0.99 and R2 = 0.97 were found between the reference methods and the NIRS predictions for the contents of oil, protein and glucosinolate, respectively. When comparing the seed quality between selfed and open pollinated plants of the parents, higher oil content (+2.2%), lower protein content (-2%) and lower glucosinolate content (-3.9 µmol/g) was observed in the open pollinated plants. The selection of single seeds resulted in significant responses to selection for oil, protein and glucosinolate content.Based on these results, it can be concluded that not only the fatty acid contents were influenced by the pollen genotype, but also contents of oil, sinigrin, gluconapoleiferin, 4-hydroxyglucobrassicin, indole glucosinolate, indole/aliphatic glucosinolate, sinapoylglucose, total sinapic acid esters, γ-tocopherol and α/γ-tocopherol. In some cases pollen influences were also observed for aliphatic glucosinolate, total glucosinolate, protein and sinapine contents.Therefore the pollen genotype has to be considered as disturbing factor when harvesting open pollinated plants and selection of single seeds in the segregating F2 generation is possible.

Microspore‐derived embryos (MDEs) of Brassica napus were used to study the influence of sucrose, jasmonic acid (JA), and abscisic acid (ABA) on dry weight and total glucosinolate (GSL) content as well as on specific GSLs. An improved procedure was developed to enable the detection of alkenyl and indole GSLs in single MDEs although they were cultured in medium containing 13% sucrose, where the accumulation of GSL is very low. A sucrose content of 2% and below in the culture medium of the embryos was necessary to significantly increase the total GSL content in embryos of three different rapeseed cultivars. The increase in total GSL content was caused predominantly by higher contents of the indole GSL glucobrassicin (GBC). Contents of 4‐hydroxy‐3‐indolyl glucosinolate (4OH), neoglucobrassicin (NEO), and 4‐methoxyglucobrassicin (4ME) were also increased. Alkenyl GSL content remained largely unaffected and increased significantly only in embryos cultured at the lowest tested sucrose concentration of 1%. Growing the embryos in the presence of JA did not change the alkenyl GSL content but led to a 7‐fold increase in the indole GSL content. Significant increases were found for GBC, 4OH and NEO, whereas 4ME content was not affected. The JA treatment did not affect the morphology or dry weight of the MDEs. In contrast, a treatment with ABA significantly reduced the dry weight and the indole GSL content of the embryos. In the combined JA and ABA treatment, the stimulative effect of JA on indole GSL biosynthesis could not override the inhibitory effect of ABA on growth and indole GSL biosynthesis of the embryos.

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Glucosinolate and isothiocyanate concentration in soil following incorporation of Brassica biofumigants

Rapeseed [Brassica napus (L.)], white mustard [Sinapis alba (L.)], and Indian mustard [Brassica juncea (L.) Czern. et Coss] belong to the family Brassicaceae. These crop species synthesize substantial amounts of fat, protein, and glucosinolates (GLS). Brassica species can differ in their concentrations of fat, protein, and GLS in response to S fertilization. Plant material for chemical analyses was harvested from a field experiment conducted in northeastern Poland in 2005 to 2008. The examined species of oilseed crops were fertilized or not fertilized with S applied to soil at optimal rates for each species based on S uptake and forecast seed yield. On average, S fertilization increased seed yield of oilseed crops by 8%, but it did not induce significant differences in the concentrations of fat and protein in seeds. Sulfur fertilization increased total GLS concentrations by 0.22 and 0.27 µmol g−1 dry matter (DM) in the root residues of white mustard and Indian mustard, respectively, and by 0.52 µmol g−1 DM in winter rapeseed. Total GLS concentration in winter rapeseed straw decreased by 0.18 µmol g−1 DM with S application. In white mustard straw, S fertilization increased total GLS concentration by 0.27 µmol g−1 DM. Sulfur fertilization increased total GLS concentrations in the seeds of spring rapeseed, white mustard and Indian mustard by 11.43, 41.75 and 32.05 µmol g−1 DM, respectively. Sulfur fertilization has a significant effect on the seed yield and biomass quality of oilseed crops of the family Brassicaceae.

Reduction of the AFs produced by Aspergillus parasiticus CECT 2681 in wheat tortillas by isothiocyanates (ITCs) from oriental and yellow mustard flours was evaluated in this study. Polyethylene plastic bags were introduced with wheat tortillas contaminated with A. parasiticus and treated with 0, 0.1, 0.5 or 0.1g of either oriental or yellow mustard flour added with 2ml of water. The wheat tortillas were stored at room temperature during 1month. The quantification of the AFs produced was analyzed by liquid chromatography (LC) coupled to the mass spectrometry detection in tandem (MS/MS). Gaseous allyl isothiocyanate (AITC) from oriental mustard was more effective than p-hydroxybenzyl isothiocyanate (p-HBITC) from yellow mustard to inhibit the production of AFs. More importantly, 1g of AITC was able to reduce >90% of AFs B1, B2, G1 and G2. p-HBITC is less stable and volatile than AITC, leading to a much lower AFs (average of 17.7 to 45.2%). Further studies should investigate the use of active packaging using oriental mustard flour and water to reduce the production of AFs by Aspergillus species in bakery goods.

Improving the productivity and stability of oilseed cropping systems through crop diversification