Prospects for a sustainable increase in the availability of long chain omega 3s: lessons from the Antarctic krill fishery.

• The global summit on nutrition, health and human behaviour (GSNHHB) identified the objective of increasing “the availability of long chain Omega‐3 (especially docosahexaenoic acid) for human consumption in a sustainable, environmentally responsible way”. • The objectives of management for sustainability include maintaining continuity of supply and limiting negative impacts. These objectives have associated challenges which are best illustrated using a case study. • Marine fisheries are likely to remain the main source of docosahexaenoic acid (DHA) for the foreseeable future. I use the example of the Antarctic krill fishery, which is a minor but high value source of DHA, to illustrate the issues, processes, actors and risks involved in attempting to manage natural resources in a sustainable, environmentally responsible way. • One of the key issues is uncertainty: The natural state of ecosystems, how they respond to exploitation, and how these responses will be affected by environmental change are not clearly understood. The solution is to use “precautionary” measures, which often means catching less than is theoretically possible, and additional restrictions on where the fishery can operate. • The “sustainability” of the Antarctic krill fishery has been questioned in a way that has impacted the delivery of Antarctic krill products to consumers. In reality, the fishery is one of only 3% of fisheries worldwide that the Food and Agriculture Organisation of the United Nations considers “under-exploited” and one of the few that have a management approach committed to limiting impacts on the both the target stock and the wider ecosystem. Disagreement arises partly because there is no universal agreement about the definitions of “sustainable” and “environmentally responsible” or about the standards of evidence required to support a claim. A potential solution is to identify the different objectives that people have for the ecosystem, and to agree acceptable trade-offs, levels of risk, and standards of evidence. This approach is compatible with the ecosystem approach to fisheries recommended by the 2002 World Summit on Sustainable Development. • The GSNHHB’s commitment to sustainability is a positive step which should be followed by engagement with suppliers to support the appropriate management and recovery of fished ecosystems. • GSNHHB’s objectives imply an increase in supply beyond the capacity of marine fisheries and therefore the development of alternative sources. • The steps towards sustainability are similar for all sources. They include identifying the different objectives that people have for the source ecosystem, evaluating the risks of not achieving these objectives, establishing trade-offs between objectives, and ensuring appropriate monitoring. It is essential for groups with an interest in source ecosystems to work with each other, and with scientists and managers, to achieve these steps

Assessing quantitative resistance against Leptosphaeria maculans (phoma stem canker) in Brassica napus (oilseed rapte) in young plants

Quantitative resistance against Leptosphaeria maculans in Brassica napus is difficult to assess in young plants due to the long period of symptomless growth of the pathogen from the appearance of leaf lesions to the appearance of canker symptoms on the stem. By using doubled haploid (DH) lines A30 (susceptible) and C119 (with quantitative resistance), quantitative resistance against L. maculans was assessed in young plants in controlled environments at two stages: stage 1, growth of the pathogen along leaf veins/petioles towards the stem by leaf lamina inoculation; stage 2, growth in stem tissues to produce stem canker symptoms by leaf petiole inoculation. Two types of inoculum (ascospores; conidia) and three assessment methods (extent of visible necrosis; symptomless pathogen growth visualised using the GFP reporter gene; amount of pathogen DNA quantified by PCR) were used. In stage 1 assessments, significant differences were observed between lines A30 and C119 in area of leaf lesions, distance grown along veins/petioles assessed by visible necrosis or by viewing GFP and amount of L. maculans DNA in leaf petioles. In stage 2 assessments, significant differences were observed between lines A30 and C119 in severity of stem canker and amount of L. maculans DNA in stem tissues. GFP-labelled L. maculans spread more quickly from the stem cortex to the stem pith in A30 than in C119. Stem canker symptoms were produced more rapidly by using ascospore inoculum than by using conidial inoculum. These results suggest that quantitative resistance against L. maculans in B. napus can be assessed in young plants in controlled conditions. Development of methods to phenotype quantitative resistance against plant pathogens in young plants in controlled environments will help identification of stable quantitative resistance for control of crop diseases