High Erucic Acid Research Articles

Can we “cultivate” erucic acid in southern Europe?

Over the last fifteen years, considerable progress has been made in the field of “green chemistry”, as regards both research aspects and market development. In particular, extraction of erucic acid (C22:1) from plants and its industrial applications have received increasing attention. At present, known species producing oils yielding large quantities of erucic acid belong, with few exceptions, to the Brassicaceae family. Among these, the two major sources of erucic acid in the world are HEAR (High Erucic Acid Rapeseed, Brassica napus var. oleifera) and crambe (Crambe abyssinica), both mainly cultivated in the USA. Their cultivation has also recently been considered and extended to southern Europe, supported by specific research projects. The quantity of erucic acid in Brassicaceae oils ranges greatly, from 55% in Crambe abyssinica to nearly zero in some varieties of Brassica napus var. oleifera. Even more differentiated and peculiar to each species and variety is adaptability to specific climatic and soil conditions. In this regard, the major limitation to the cultivation of some interesting Brassicaceae species, crambe in particular, is their poor tolerance to cold. Among Brassicaceae producing erucic acid, the less frequently cultivated species, such as Brassica juncea and B. carinata, if grown in areas with relatively mild winters, may give yields of seed and oil similar to those of the most productive rapeseed genotypes. Within this framework, in order to achieve high production of erucic acid, it is essential to identify the most productive genotypes, among available species, for each environment. In this report, seed and oil productions of some important Brassicaceae species for extraction of erucic acid, derived from 15 years of field trials in northern Italy, are discussed in relation to the possibility of autumn or spring sowing.

Comparison of pedigree selection and doubled haploid breeding methods for high erucic acid rapeseed cultivar development

Sixty families from pedigree selection and 60 lines from doubled haploid development per cross, for three different Brassica napus L. high erucic acid rapeseed (HEAR) crosses, were created and then compared for agronomic and seed quality performance in four environments in Manitoba in 2000 and 2001. Differences in mean performance for many traits were observed within crosses; however, these differences were not consistent among crosses. Similarly, there were differences observed in ranges for many traits within crosses but with few clear trends among crosses. Similar numbers of superior pedigree selection families and doubled haploid lines within and among crosses for individual traits and for combinations of all traits were found in this study. Financial and temporal resource requirements for these two breeding methods were found to be similar. It is concluded that both pedigree selection and doubled haploid breeding methods have their particular strengths and weaknesses but that neither is clearly superior for the development of B. napus HEAR cultivars. Key words: Brassica napus L., HEAR, breeding method comparisons

Yield of Brassica napus L. hybrids developed using resynthesized rapeseed material sown at different locations

The utilisation of resynthesized Brassica napus (RS) genotypes in commercial breeding programmes is restricted to the development of intraspecific hybrids, so-called semi-synthetic rapeseed, and backcross progenies. In order to determine the general combining ability (GCA) of different rapeseed material, nine high-erucic acid RS lines and three old spring rapeseed cultivars were used as pollinators of male sterile double-low spring rapeseed lines (MSL-system). Yield performance of the single-cross hybrids was tested in a multi-location field trial that revealed a high yield potential of semi-synthetic rapeseed hybrids based on RS lines. The use of such resynthesized rapeseed forms in developing rapeseed hybrids and their possible use in future oilseed breeding is discussed.

First Report of an Alternaria Leaf Spot Caused by Alternaria brassicae on Crambe abyssinicia in Australia.

Crambe abyssinicia Hochst. is grown sporadically worldwide for its value as a source of high erucic acid industrial oils and secondary commercial products. While there is increasing interest in cropping C. abyssinicia in Australia, for these potentials and also as a source of oil for biodiesel production, currently, there have been no commercial crops of this species. In September 2004, inspection of a small experimental field crop in Beverley, Western Australia indicated the presence of significant leaf spotting just prior to commencement of flowering. The symptoms of this disease included as many as 10 to 15 spot lesions per leaf that were generally rounded and varied between 0.5 to 11 mm in diameter. Clusters of these lesions were often associated with chlorosis of the region of leaves where they occurred. More than 95% of plants inspected showed these symptoms. When affected leaves were incubated in moist chambers, typical conidia of Alternaria brassicae (Berk.) Sacc. were observed. The description of these conidia matched that of the Commonwealth Mycological Institute for this pathogen (1) showing obclavate conidia 105 to 210 μm long and 20 to 30 μm thick, with 11 to 15 transverse septa and 0 to 3 longitudinal or oblique septa, predominantly with a pronounced beak 5 to 8 μm thick extending 0.3 to 0.5 μm of the length of the conidium. Single-spore isolations were made onto potato dextrose agar. Subcultures of these isolates were identified using a polymerase chain reaction (PCR)- based assay (2). This assay involved the use of two sets of A. brassicae-specific primers selected for conventional and real-time PCR. The colonies were confirmed to belong to A. brassicae. In a pathogenicity test to confirm Koch's postulates, single-spore isolates were inoculated onto cotyledons and leaves of 10-day-old C. abyssinicia seedlings. Symptoms on inoculated plants appeared within a period of 14 days of inoculation, matching those found on the affected plants in the field, and A brassicae was reisolated. A. brassicae causes an important worldwide disease of crucifers, for example, it can be a devastating disease of rapeseed and the other cruciferous crops in the United States and Canada. Since A. brassicae has already been reported on other species of crucifers Australia-wide, it may pose a threat to any potential Crambe spp. industry in this country.

Increased levels of erucic acid in Brassica carinata by co-suppression and antisense repression of the endogenous FAD2 gene

Erucic acid and its derivatives represent important industrial feedstock compounds, and there is an increasing demand for the production of high erucate oils in this regard. Our goal therefore, is to develop high erucic acid (HEA) Brassicaceae lines with increased proportions of erucic acid and very long-chain fatty acids (VLCFAs). We proposed that oleate availability may be a rate-limiting factor in the biosynthesis of erucic acid. We have tried to address this question by manipulating the expression of the endogenous FAD2 gene in B. carinata using co-supression and antisense approaches. Both methods resulted in transgenic lines exhibiting decreased proportions of polyunsaturated C 18 fatty acids (18:2+18:3) and concomitant and significantly increased proportions of 18:1, 22:1 and total VLCFAs. Co-suppressed FAD2 B. carinata lines exhibited 3–18% decreases in 18:2, 22–49% decreases in 18:3 and significantly increased proportions of 18:1 (36–99%), 22:1 (12–27%) and VLCFAs (6–15%). Transgenic B. carinata lines developed using an antisense FAD2 approach exhibited decreased proportions of 18:2 and 18:3 (9–39% and 33–48%, respectively) and significantly increased proportions of 18:1 (54–130%), 22:1 (5–19%) and VLCFAs (6–21%). The possibility of using these approaches to produce prototype transgenic germplasm of the Brassicaceae accumulating seed oils with improved proportions of erucic and other VLCFAs is discussed.

STRUCTURED TRIACYLGLYCEROLS CONTAINING BEHENIC ACID: PREPARATION AND PROPERTIES

ABSTRACT Low‐calorie structured lipids (SL) containing behenic and oleic acids were prepared using interesterification of olive oil with hydrogenated high erucic acid rapeseed oil and acidolysis of olive oil with behenic acid. The reactions were catalyzed by the Lipozyme RM IM enzyme. Triacylglycerols (TAGs), obtained by interesterification (TAG SLHE ), contained 20.9 and 45.3% of behenic and oleic acids, respectively, whereas those obtained by acidolysis (TAG SLB ) contained 34.6 and 49.6% of these acids, respectively. In both cases, behenic acid was mainly incorporated in the sn‐1,3 positions of the TAG molecules (∼93%). The distribution of oleic acid in the individual positions was different for each product. The content of oleic acid in the sn‐2 position of TAG was 50.2 and 80.3% for TAGSLHEand TAGSLB, respectively. The melting temperature of TAGSLHE(45.5%) was higher than that of TAGSLB(37.5%). Because of the suitable solid fat content characteristics of TAGSLBas a function of temperature, it is possible to use TAGSLBin bakery and in confectionery industries for production of margarines and blends, among others.

ENZYMATIC ISOLATION AND ENRICHMENT OF ERUCIC ACID FROM HEA SEED OILS: CURRENT STATUS

Erucic acid (EA), a fatty acid of 22-carbon chain with one isolated double bond, has broad industrial applications.Currently, erucic acid is isolated from Crucifereae plant oils through steam splitting, namely the Colgate-Emery process,followed by fractional distillation. This two-step process involves drastic conditions, low energy efficiency, and extensiveproduct degradation. Enzymatic approaches, on the other hand, have many advantages including mild operating conditionsand high selectivities. To develop a more efficient alternative process, researchers have studied enzymatic approaches for EAisolation and enrichment for about two decades. Lipases have shown three types of specificities in catalyzing high-erucic-acid(HEA) oils, namely fatty-acid-specific, region-specific, and non-specific. With lipases of certain specificities, variousprocesses of hydrolysis, esterification, interesterification, and transesterification have been studied. Research has also beenconducted on investigating the effects of process parameters, including operating temperature, lipase content, and watercontent, on the process efficiency. The enzymatic approach has shown its potential in isolating and enriching EA from differentCrucifereae seed oils. This article reviews the current status of the studies, especially the performance of different lipases andcorresponding enzymatic reactions, for EA enrichment from Crucifereae plant oils.

Temporal gene expression of 3-ketoacyl-CoA reductase is different in high and in low erucic acid Brassica napus cultivars during seed development

The membrane-bound acyl-CoA elongase complex is a key enzyme responsible for erucoyl-CoA synthesis. Among the four putative genes encoding the four moieties of this complex in Brassica napus seeds, only one has been characterized, the Bn-fae1 gene, which encodes the 3-ketoacyl-CoA synthase. The genes encoding the other enzymes (3-ketoacyl-CoA reductase, 3-hydroxyacyl-CoA dehydratase and trans-2,3-enoyl-CoA reductase) have not been identified. We cloned two 3-ketoacyl-CoA reductase cDNA isoforms, Bn-kcr1 and Bn-kcr2, from B. napus seeds. Their function was identified by heterologous complementation in yeast by restoring elongase activities. The comparison of Bn-kcr mRNA expression in different B. napus tissues showed that the genes were preferentially expressed in seeds and roots. We also investigated the regulation of gene expression in High Erucic Acid Rapeseed (HEAR) and in Low Erucic Acid Rapeseed (LEAR) cultivars during seed development. The co-expression of Bn-fae1 and Bn-kcr observed in HEAR cultivar during seed development was different in LEAR cultivar, suggesting that expression of both genes was directly or indirectly linked.

Capillary gas chromatography analysis of Ethiopian mustard to determine variability of fatty acid composition

AbstractEthiopian mustard (Brassica carinata A. Braun) is an oil crop grown in Ethiopia. However, the oil is considered low quality, as it contains long chain monounsaturated fatty acids, mainly erucic acid. High erucic acid content is beneficial for the polymer industry, whereas low erucic acid is recommended for food purposes. Both linoleic and linolenic acids are essential fatty acids; however, less than 3% linolenic acid is preferred for oil stability. The objectives of this study were to determine fatty acid composition of Ethiopian mustard to determine the range of genetic diversity for these traits. The genotypes were analysed by capillary gas chromatography (CGC). Twenty‐six fatty acids were identified. In all accessions, the predominant fatty acids were erucic, linoleic, α‐linolenic and oleic, followed by gadoleic and palmitic. To a lesser extent stearic, vaccinic, nervonic and behenic acids were found in all accessions. Significant correlations were found between palmitic acid and stearic acid (positive), between erucic acid and palmitic, stearic, vaccinic, oleic, linoleic and α‐linolenic acids (negative) and eicosenoic acid (positive). Selection and hybridization techniques can be applied to modify the oil content of Ethiopian mustard, considering the variability observed. Copyright © 2004 Society of Chemical Industry

Allelic variation in linolenic acid content of high erucic acid Ethiopian mustard and incorporation of the low linolenic acid trait into zero erucic acid germplasm

AbstractZero erucic acid germplasm of Ethiopian mustard is characterized by high levels of linolenic acid (about 21%). Two genetic sources of low linolenic acid (N2‐4961 and HF‐186, about 5%), have been developed in a high erucic acid background. The objectives of this research were to study the genetic relationship between the two low linolenic acid lines and to transfer the trait to zero erucic acid germplasm. F1 seed generations from crosses between both lines had higher average linolenic acid concentration than both parents. F2 seeds segregated for linolenic acid content following a continuous variation from 1.8 to 7.4%, exceeding the limits of the parental distribution ranges. Transgressive recombinants with very low linolenic acid concentration (0.7‐2.7%) were confirmed in the F3 seed generation. The results suggested that N2‐4961 and HF‐186 possess alleles for low linolenic acid at different loci. Transgressive low linolenic acid F3 plants were crossed with plants of a zero erucic acid line and a selection for zero erucic, low linolenic acid was conducted. As a result, a zero erucic acid F3:4 line containing 1.5 ± 0.7% linolenic acid was developed.

A rapid chromatographic method for determining the glucosinolate content in crambe seed

Abstract Crambe abyssinica is becoming a reliable source of industrial oil with good technical characteristics because of its high erucic acid content. The possibility of using the industrial defatted meal of crambe as a feed could further promote the interest in this crop, but is prevented by the high glucosinolate content (70‐150 μmol/g). Therefore the possibility of reducing this parameter by selection was evaluated and a search for a new quick analytical procedure begun. When hydrolysed by myrosinase (thioglucoside glucohydrolase EC 3.2.3.1.), at pH 6.5 or higher, epiprogoitrin, the main glucosinolate in crambe seed (>90% of total glucosinolates), gives (5R)‐5‐vinyl‐1,3‐oxazolidine‐2‐thione quantitatively. The latter can be easily estimated by high‐performance liquid chromatography. This is the background of the proposed analytical procedure that permits rapid analysis of about 100 samples per day using about 25 mg of crambe meal (five seeds) for assay. The method can also be used to select for glucosinolate content in rapeseed and, probably with some adjustment, all crops that have a 2‐hydroxy‐glucosinolate as the main glucosinolate.

Molecular mapping of seed aliphatic glucosinolates in Brassica juncea.

An RFLP genomic map with 316 loci was used to study the inheritance of aliphatic glucosinolates in Brassica juncea using doubled-haploid (DH) populations developed from a cross between RLM-514, an agronomically superior non-canola quality B. juncea (high erucic acid and high glucosinolates), and an agronomically poor canola quality B. juncea breeding line. Two QTLs (GSL-A2a and GSL-A2b) associated with 3-butenyl were consistent across years and locations, and explained 75% of the phenotypic variance in the population. Three QTLs (GSL-A2a, GSL-F, GSL-B3) affected 2-propenyl and explained 78% of the phenotypic variance in the population. For total aliphatic glucosinolates, five QTLs explained 30% to 45% of the total phenotypic variance in the population in different environments. Several QTLs (GSL-A7 and GSL-A3) were highly inconsistent in different environments. Major QTLs (GSL-A2a and GSL-A2b) associated with individual glucosinolates were non-significant for total aliphatic glucosinolates. A marker-assisted selection strategy based on QTLs associated with individual glucosinolates rather than total aliphatic glucosinolates is proposed for B. juncea.

Development of rapeseed with high erucic acid content by asymmetric somatic hybridization between Brassica napus and Crambe abyssinica.

PEG-induced asymmetric somatic hybridization between Brassica napus and Crambe abyssinica was carried out. C. abyssinica is an annual cruciferous oil crop with a high content of erucic acid in the seed oil valuable for technical purposes. UV-irradiated mesophyll protoplasts of C. abyssinica cv 'Carmen' and cv 'Galactica' were fused with hypocotyl protoplasts of different genotypes of B. napus cv 'Maplus' and breeding line '11502'. Shoot regeneration frequency varied between 6.1% and 20.8% among the different doses of UV-irradiation, ranging from 0.05 J/cm(2) to 0.30 J/cm(2). In total, 124 shoots were regenerated, of which 20 asymmetric somatic hybrids were obtained and verified by nuclear DNA content and AFLP analysis. AFLP data showed that some of the characteristic bands from C. abyssinica were present in the hybrids. Cytological analysis of these hybrids showed that 9 out of 20 asymmetric hybrids had 38 chromosomes, the others contained 40-78 chromosomes, having additional chromosomes between 2 and 40 beyond the 38 expected for B. napus. The investigation into the fertility of asymmetric somatic hybrids indicated that the fertility increased with increasing UV-doses ranging from 0.05 J/cm(2) to 0.15 J/cm(2). All of the hybrids were cultured to full maturity, and could be fertilized and set seeds after self-pollination or backcrosses with B. napus. An analysis of fatty acid composition in the seeds was conducted and found to contain significantly greater amounts of erucic acid than B. napus. This study indicates that UV-irradiation could be used as a tool to produce asymmetric somatic hybrids and to promote the fertility of the hybrids.

Inheritance of Increased Oleic Acid Concentration in High-Erucic Acid Ethiopian Mustard

In comparison with canola oil, zero-erucic acid Ethiopian mustard (Brassica carinata A. Braun) oil is characterized by a low concentration of the monounsaturated oleic acid and high concentrations of the polyunsaturated linoleic acid and linolenic acid. Because of the low oxidative stability of oils rich in polyunsaturated fatty acids, the increase of oleic acid concentration in zero-erucic acid Ethiopian mustard is needed. Increased oleic acid concentration is currently available only in high erucic acid backgrounds. The objective of the present research was to study the inheritance of increased oleic acid concentration in the high-erucic acid Ethiopian mustard mutant N2-3591. The mutant was reciprocally crossed with the high-erucic acid line C-101, with the standard composition of C18 fatty acids. Partial maternal and cytoplasmic effects for oleic acid concentration were observed in the analysis of F1 seeds and F1 plants, respectively, from reciprocal crosses. Standard oleic acid concentration in C-101 was partially dominant over increased oleic acid concentration in N2-3591. Oleic acid concentration of F2 seeds segregated following a 3:1 (standard–intermediate: increased) ratio, suggesting monogenic inheritance. This was confirmed in the BC1 to N2-3591, which segregated following a 1:1 (intermediate: increased) ratio. The separation of the standard and intermediate oleic acid classes was not possible, probably because of the partial dominance of standard over increased oleic acid concentration. The monogenic inheritance of increased oleic acid levels in the high-erucic acid N2-3591 line will facilitate the transfer of this trait to zero-erucic acid Ethiopian mustard germplasm.

Inheritance of Increased Oleic Acid Concentration in High‐Erucic Acid Ethiopian Mustard

In comparison with canola oil, zero‐erucic acid Ethiopian mustard (Brassica carinata A. Braun) oil is characterized by a low concentration of the monounsaturated oleic acid and high concentrations of the polyunsaturated linoleic acid and linolenic acid. Because of the low oxidative stability of oils rich in polyunsaturated fatty acids, the increase of oleic acid concentration in zero‐erucic acid Ethiopian mustard is needed. Increased oleic acid concentration is currently available only in high erucic acid backgrounds. The objective of the present research was to study the inheritance of increased oleic acid concentration in the high‐erucic acid Ethiopian mustard mutant N2‐3591. The mutant was reciprocally crossed with the high‐erucic acid line C‐101, with the standard composition of C18 fatty acids. Partial maternal and cytoplasmic effects for oleic acid concentration were observed in the analysis of F1 seeds and F1 plants, respectively, from reciprocal crosses. Standard oleic acid concentration in C‐101 was partially dominant over increased oleic acid concentration in N2‐3591. Oleic acid concentration of F2 seeds segregated following a 3:1 (standard–intermediate: increased) ratio, suggesting monogenic inheritance. This was confirmed in the BC1 to N2‐3591, which segregated following a 1:1 (intermediate: increased) ratio. The separation of the standard and intermediate oleic acid classes was not possible, probably because of the partial dominance of standard over increased oleic acid concentration. The monogenic inheritance of increased oleic acid levels in the high‐erucic acid N2‐3591 line will facilitate the transfer of this trait to zero‐erucic acid Ethiopian mustard germplasm.

Modification of glucosinolate and erucic acid contents in doubled haploid lines of Brassica carinata by UV treatment of isolated microspores

Ethiopian mustard (Brassica carinata Braun) is a potential oil crop for the Mediterranean area. The objective of this study was to develop an efficient system of mutagenesis using ultraviolet (UV) light irradiation of isolated microspores from Brassica carinata. From the survival curve based on embryo yield after irradiation of the microspores with UV light, the LD50 was estimated to be an exposure of 8 min. Total content of glucosinolates and fatty acid composition were analysed in the seeds of the doubled haploid homozygous plants with the purpose of selecting lines with modified glucosinolate and erucic acid contents. Three groups of doubled haploid lines exhibiting low and high glucosinolate contents, and high erucic acid content have been identified from a population of 270 doubled haploid lines. In eight lines, the content of glucosinolates was reduced from an average of 80.6 μmol g-1 seed to 37.5 μmol g-1 seed, whereas in four lines, the content of glucosinolates was increased up to 99.2 μmol g-1 seed. In six additional lines, the content of erucic acid was increased from 42.8% in the nontreated lines to 49.5% of the totalfatty acid composition in some of the mutant lines. All lines showed stablelevels of erucic acid in two generations, the M2 and M3.

Metabolic engineering of fatty acids for breeding of new oilseed crops: strategies, problems and first results

Abbreviations: ACP = acyl carrier protein. – ACS = acyl-CoA synthase. – ARA = arachidonic acid. – CLA = conjugated linoleic acid. – CPT = CDP-choline :1,2-diacylglycerol cholinephosphotransferase. – DAGAT = acyl-CoA :1,2-diacylglycerol acyltransferase. – DHA = docosahexaenoic acid. – EPA = eicosapentaenoic acid. – ER = endoplasmic reticulum. – FAE = fatty acid elongase. – FAR = acyl-CoA reductase. – GLA = γ-linolenic acid. – GPAT = acyl-CoA : glycerol-3-phosphate acyltransferase. – HEAR = high-erucic acid rapeseed. – KAS = β-ketoacyl-ACP synthase. – KCS = β-ketoacyl-CoA synthase. – LPAAT = acyl-CoA : lysophosphatidic acid acyltransferase. – LPCAT = acyl-CoA : lysophosphatidylcholine acyltransferase. – MCF = medium-chain fatty acids. – mRNAi = antisense messenger ribonucleic acid containing inverted-repeat sequences. – PC = phosphatidylcholine. – PDAT = phospholipid : 1,2-diacylglycerol acyltransferase. – PLA2 = phospholipase A2. – TAG = triacylglycerol. – VLCPUFA = very long-chain polyunsaturated fatty acids. – WS = wax synthase

Restoring enzyme activity in nonfunctional low erucic acid Brassica napus fatty acid elongase 1 by a single amino acid substitution.

Genomic fatty acid elongation 1 (FAE1) clones from high erucic acid (HEA) Brassica napus, Brassica rapa and Brassica oleracea, and low erucic acid (LEA) B. napus cv. Westar, were amplified by PCR and expressed in yeast cells under the control of the strong galactose-inducible promoter. As expected, yeast cells expressing the FAE1 genes from HEA Brassica spp. synthesized very long chain monounsaturated fatty acids that are not normally found in yeast, while fatty acid profiles of yeast cells expressing the FAE1 gene from LEA B. napus were identical to control yeast samples. In agreement with published findings regarding different HEA and LEA B. napus cultivars, comparison of FAE1 protein sequences from HEA and LEA Brassicaceae revealed one crucial amino acid difference: the serine residue at position 282 of the HEA FAE1 sequences is substituted by phenylalanine in LEA B. napus cv. Westar. Using site directed mutagenesis, the phenylalanine 282 residue was substituted with a serine residue in the FAE1 polypeptide from B. napus cv. Westar, the mutated gene was expressed in yeast and GC analysis revealed the presence of very long chain monounsaturated fatty acids (VLCMFAs), indicating that the elongase activity was restored in the LEA FAE1 enzyme by the single amino acid substitution. Thus, for the first time, the low erucic acid trait in canola B. napus can be attributed to a single amino acid substitution which prevents the biosynthesis of the eicosenoic and erucic acids.

Erucic acid heredity in Brassica juncea ‐ some additional information

AbstractGenetic studies were undertaken to reassess erucic acid heredity in Brassica juncea. Analysis of segregation in F2 and BC1 generations from two zero × high erucic acid crosses indicated that higher erucic acid in B. juncea was controlled by two dominant genes with additive effects, whereas segregation in a cross involving ‘CCWF 16′, a genotype having intermediate erucic acid (25.6%), and a zero erucic acid strain, indicated monogenic dominant control for intermediate erucic acid content. The B. juncea strain ‘CCWF 16’ was developed by hybridizing high‐erucic acid B. juncea cv.‘WF‐1’ with a ‘0’ erucic B. rapa cv.‘Candle’ followed by backcrossing with ‘WF‐1’ and half‐seed selection for low erucic acid in each backcross generation. This strategy resulted in substitution of the high erucic acid allele present in the A genome of B. juncea (AABB) by the zero erucic acid allele associated with ‘A’ genome of ‘Candle’. The intermediate erucic acid content in ‘CCWF 16’ was thus attributed to a gene present in the ‘BB’ genome. Experimental data clearly suggested that the gene (E2) associated with the A genome had a greater contribution to the total erucic acid content in B. juncea than the gene (E1) located on the B genome. This provided experimental evidence for a previous suggestion of unequal contributions of two dominant genes (E1= 12%, E2= 20%) to high erucic acid content in conventional digenomic Brassica species.

Fatty acid composition of resynthesized Brassica napus and trigenomic Brassica void of genes for erucic acid in their A genomes

AbstractThe fatty acid composition of seed oil of four interspecific hybrids, resulting from crosses between zero erucic acid Brassica rapa (AA), and high erucic acid Brassica alboglabra/Brassica oleracea (CC) and Brassica carinata (BBCC), void of erucic acid genes in their A‐genomes was examined. The erucic acid content in resynthesized Brassica napus (AACC) lines derived from these crosses was only about half that of the high erucic acid CC genome parents, indicating equal contributions of the two genomes to oil (fatty acid) synthesis and accumulation. The differences in C18 fatty acid synthesis between the parents were also evident in the resulting resynthesized B. napus plants. Hexaploid Brassica plants of the genomic constitution AABBCC, in which the AA genome was incapable of erucic acid synthesis, had lower erucic acid contents than the B. carinata (BBCC) parent. This is plausible considering the fact that the zero erucic acid AA genome contributes to oil synthesis in AABBCC plants, thus reducing erucic acid content.