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Plant seeds have long been promoted as a production platform for novel fatty acids such as the ω3 long-chain (≥ C20) polyunsaturated fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) commonly found in fish oil. In this article we describe the creation of a canola ( Brassica napus ) variety producing fish oil-like levels of DHA in the seed. This was achieved by the introduction of a microalgal/yeast transgenic pathway of seven consecutive enzymatic steps which converted the native substrate oleic acid to α-linolenic acid and, subsequently, to EPA, docosapentaenoic acid (DPA) and DHA. This paper describes construct design and evaluation, plant transformation, event selection, field testing in a wide range of environments, and oil profile stability of the transgenic seed. The stable, high-performing event NS-B50027-4 produced fish oil-like levels of DHA (9–11%) in open field trials of T3 to T7 generation plants in several locations in Australia and Canada. This study also describes the highest seed DHA levels reported thus far and is one of the first examples of a deregulated genetically modified crop with clear health benefits to the consumer.

Aquaculture plays an important role in providing protein and fatty acids to meet human nutritional requirements. The finite supply of marine ingredients has led to increased use of vegetable oils in aquafeed. While these oils can meet energy and growth needs, they lack nutritionally required ω3 long-chain polyunsaturated fatty acids (ω3 LCPUFAs). Development of land-based alternative oil sources to safeguard global aquaculture production, while meeting the nutritional needs of both fish and human consumers, is critical. This review summarizes studies using a new land-based ω3 LCPUFA canola oil in fish feed to support both energy and ω3 LCPUFA requirements of Atlantic salmon during each phase of the life cycle, while producing fish with adequate ω3 LCPUFA content to meet human nutritional needs. In all cases, growth and performance were comparable to fish fed conventional fish-oil-based diets; no adverse effects were attributed to the use of ω3 canola oil. Fatty acid deposition in muscle (fillet) reflected feed composition, resulting in accumulation of alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) and a low ω6:ω3 ratio, making salmon fed ω3 LCPUFA canola oil a sustainable source of these nutrients for human consumption. Additionally, reduced melanin deposits were observed in fish fed ω3 LCPUFA canola oil.

Phloem transport of D,L-[(14)C]glufosinate, D-[(14)C]glufosinate, and acetyl-L-[(14)C]glufosinate, was examined in the susceptible Brassica napus cv Excel and a glufosinate-resistant genotype (HCN27) derived by transformation of cv Excel with the phosphinothricin-N-acetyltransferase (pat) gene. Considerably more (14)C was exported from an expanded leaf in HCN27 than in cv Excel following application of D,L-[(14)C]glufosinate (25% versus 6.3% of applied, respectively, 72 h after treatment). The inactive isomer, D-glufosinate, was much more phloem mobile in cv Excel than racemic D,L-glufosinate. Foliar or root supplementation with 1 mM glutamine increased D,L-[(14)C]glufosinate translocation in cv Excel but only transiently, suggesting that glutamine depletion is not the major cause of the limited phloem transport. Acetyl-L-[(14)C]glufosinate (applied as such or derived from L-glufosinate in pat transformants) was translocated extensively in the phloem of both genotypes. Acetyl-L-[(14)C]glufosinate was readily transported into the floral buds and flowers, and accumulated in the anthers in both genotypes. These results suggest that phloem transport of D,L-glufosinate is limited by rapid physiological effects of the L-isomer in source leaf tissue. The accumulation of acetyl-L-glufosinate in the anthers indicates that it is sufficiently phloem mobile to act as a foliar-applied chemical inducer of male sterility in plants expressing a deacetylase gene in the tapetum, generating toxic concentrations of L-glufosinate in pollen-producing tissues.

A biotype of Stellaria media (L.) Vill. has been identified that is highly resistant to the herbicide chlorsulfuron. Resistance is due to an altered acetolactate synthase (ALS) that is much less sensitive to chlorsulfuron than the ALS from the susceptible (S) biotype. The S biotype was extremely sensitive to D489 (N-[2,6-dichlorophenyl]-5,7-dimethyl-1,2,4-triazolo[1,5a]pyrimidine-2-sulfonamide), a number of a new class of triazolopyrimidine herbicides, while the chlorsulfuron-resistant biotype exhibited complete cross-resistance at both the whole plant and enzyme levels. ALS activity of the S biotype was reduced by approximately 90% in the presence of 0.1 micromolar D489, while that of the R biotype was reduced by less than 10%. This result suggests that the two herbicides share a common binding site on ALS. Only very slight cross-resistance at the ALS level was found to imazamethabenz, an imidazolinone herbicide

Treatment of field pennycress (Thlaspi arvense L.) leaves with the herbicide chlorsulfuron resulted in a decrease in the export of assimilate. Twelve hours after a spot application of 1 microgram, assimiliate translocation was 70% of that in control leaves. In excised leaves treated with chlorsulfuron the total amounts of sugars and free amino acids were 150 and 170%, respectively, of the amounts in control leaves, 30 hours after herbicide treatment. The amount of sucrose was 247% of that in control leaves. The increase in the concentration of sucrose in the chlorsulfuron-treated leaves, combined with the absence of an effect of chlorsulfuron on carbon dioxide fixation, suggests that the decrease in assimilate transport is not due to an effect on the synthesis of assimilates, but rather to an effect on their movement out of the leaves. Supplying branched-chain amino acids to the field pennycress seedlings prior to the application of chlorsulfuron prevented the occurrence of the effects described

A false cleavers population that survived treatment with triasulfuron/bromoxynil in 1996 was identified in central Alberta, Canada, in a field that had been treated with acetolactate synthase (ALS) inhibitors in 3 of the previous 6 yr. In greenhouse studies, this biotype was highly resistant to the ALS inhibitors triasulfuron, thifensulfuron/tribenuron, and sulfometuron and moderately resistant to imazethapyr; GR50, values were > 16, > 5, > 1.0, and 9.9, respectively. In addition, cross-resistance was identified to the auxin-type herbicide quinclorac (GR50 value > 6.7) but not to fluroxypyr (GR50 value 1) or MCPA/mecoprop/dicamba. Quinclorac had not been used previously in this field. Analysis of ALS extracted from the resistant biotype and a susceptible biotype from a nearby location indicated that resistance to ALS inhibitors was due to an altered target site with reduced sensitivity to a broad range of ALS inhibitors. The ALS I50 values for triasulfuron, metsulfuron, chlorsulfuron, thifensulfuron, and imazethapyr were 36, 34, 92, 96, and 14 times higher, respectively, for the resistant compared to the susceptible biotype. The mechanism of resistance to quinclorac is unknown. This is the first report of high-level herbicide resistance in this weed species.

The herbicides chlorsulfuron and clopyralid were taken up rapidly by excised pea root tissue and accumulated in the tissue to concentrations ten and four times those in the external medium, respectively. Uptake was related linearly to external herbicide concentration over a wide concentration range, implying that transport across the membrane is by nonfacilitated diffusion. Uptake of both compounds was influenced by pH, with greatest uptake at low pH. The pH dependence of uptake suggests that the herbicides (both of which are weak acids) are transported across the plasma membrane in the undissociated form, and accumulate in the cytoplasm by an ion trap mechanism. Most of the absorbed herbicide effluxed from the tissue when it was transferred to herbicide-free buffer, indicating that the accumulation was not due to irreversible binding. Consequently, both herbicides remain available for transfer to the phloem. These results can explain the high reported phloem mobility of clopyralid in intact plants. The low phloem mobility of chlorsulfuron must be accounted for by factors that override its ability to accumulate in the symplast.

Laboratory experiments were conducted to determine the mechanism of resistance to diclofop in two wild oat biotypes (designated 'B' and 'C' biotypes) from the Willamette Valley of Oregon. Resistance could not be attributed to differential absorption, translocation, or metabolism of diclofop. Resistance was not correlated with membrane plasmalemma repolarization following diclofop acid treatment. Compared to a susceptible ('S') wild oat biotype, acetyl CoA carboxylase from the B and C biotypes showed a 10.3 and 4.5 fold increase in the level of resistance, respectively, to diclofop acid. Cross-resistance to fenoxaprop acid was 5.5 and 7.3 times higher in the B and C biotypes, respectively than the S biotype. Correlation between resistance at the whole plant level and at the ACCase level was good for diclofop and fenoxaprop in the B biotype. For the C biotype, this correlation was not as good. Possible reasons for the discrepancy are given.