The significance of African vegetables in ensuring food security for South Africa’s rural poor

Technologies and services provided to resource-poor farmers need to be relevant and compatible with the context in which they operate. This paper examines the contribution of extension services to the food security of resource-poor farmers in a rural village in South Africa. It considers these in terms of the local context and the production of African vegetables in household food plots. A mixture of participatory, qualitative and quantitative research tools, including a household survey, is used to argue that local production practices contribute more to food security requirements than the extension services. This is because of the ability of African vegetables to grow relatively well in semi-arid areas where other exotic plants do not, their ability to provide at least two foodstuffs during their life cycle, and the ability of either the fruit or the leaves, or both, to be dried and stored for consumption in the winter months. These crops can make a significant contribution in terms of household food security, but a number of social and agroecological factors are constraining their production and placing their availability under threat. Despite this, the extension services remain focused on certain activities within vegetable garden projects, even when these are not meeting their proposed purpose—food security by means of cash-crop production. The paper concludes that social and agroecological constraints could be improved if the extension services were changed. This could include the use of context specific and low-cost technologies to ensure that these crops are able to increase their contribution to household food security for resource-poor farmers in semi-arid areas.     

Striking a balance between retaining populations of protected seahorses and maintaining swimming nets

• 1. The fish family Syngnathidae (seahorses, pipefish, pipehorses and seadragons) is fully protected in New South Wales, Australia, but in some countries certain species are threatened by unsustainable collecting, capture as incidental bycatch, and habitat degradation.
• 2. Within Sydney Harbour, two species of seahorses (Hippocampus abdominalis and Hippocampus whitei) have been found to colonize artificial structures such as jetty pylons and protective netted swimming enclosures. These protective nets are subject to fouling from epibiotic growth (algae, ascidians, bryozoans, etc.) and rubbish, which causes the nets to collapse from the additional weight. Local authorities employ diving contractors on an ad hoc basis to remove the epibiota from nets.
• 3. Surveys showed a significant decline in the numbers of both seahorse species at one site following the replacement of a net, and recovery of the H. whitei population took more than 15 months.
• 4. A manipulative experiment tested the importance of epibiotic growth for seahorses. H. whitei, tagged with individual marks, were allocated to sections of a net that had undergone different cleaning procedures. Seahorse size, position on the net and total population abundance were recorded every 2 weeks over a 3 month period. It was demonstrated that seahorses have a significant positive association with epibiotic growth and proximity to the sea floor. Seahorse populations also showed seasonal variation in abundance with increased numbers on the net during the breeding season (spring–summer).
• 5. This project has led to the development of best practice net cleaning procedures for local authorities in Sydney Harbour to manage growth on the nets while minimizing impacts on seahorse populations. Copyright © 2009 John Wiley & Sons, Ltd.

     

Effect of the duration of inoculum exposure on development of citrus canker symptoms on seedlings of Swingle citrumelo

Citrus canker (Xanthomonas citri subsp. citri, Xcc) is one of the most serious diseases citrus in Florida, and elsewhere in the world. The disease causes yield loss and some fresh fruit trade restrictions may apply. Cultural management techniques such as windbreaks may work by not only reducing wind speed, but also reducing the period of exposure of susceptible foliage or fruit to those wind speeds that support infection from incoming inoculum. To investigate the effect of exposure period to inoculum of Xcc, seedlings of canker-susceptible Swingle citrumelo were exposed to sprayed inoculum for increasing periods at different wind speeds. The incidence and severity of citrus canker was assessed. In three experiments the incidence and severity of citrus canker most often increased with longer periods of exposure to inoculum, especially so at wind speeds of ≥16 m/s compared to wind speeds of ≤5 m/s (wind speed also increased disease incidence and severity). Regression analysis demonstrated relationships between period of exposure to inoculum and the percent infected leaves per plant, the number of lesions per plant, the number of lesions per infected leaf, and for the percent of infected leaves with lesions on the petioles at wind speeds of ≥16 m/s (R²?=?0.16–0.72). Due to the effect of inoculum exposure period and wind speed, attempts should be made to minimize exposure of canker-susceptible citrus when wind speed is highest and inoculum is available. Windbreaks should help minimize periods of exposure to splashed inoculum in high winds.     

Characterisation of the first wheat (Triticum aestivum L.) nucleotide pyrophosphatase/phosphodiesterase resembling mammalian counterparts

A formerly unknown nucleotide pyrophosphatase/phosphodiesterase (NPP) of wheat (Triticum aestivum L.) (TaNPP) was recombinantly produced in Pichia pastoris (TaNPPr) following assembly of the sequence out of wheat ESTs using sequences of known NPPs. Simultaneously, a phosphodiesterase was purified to homogeneity from wheat germs, characterised and identified as TaNPP. TaNPP contains the highly conserved catalytic substrate and metal binding residues and displays properties [high pH optimum, glycosylation, high thermostability and inhibition by EDTA and adenosine 5′-monophosphate (AMP)] similar to those of mammalian enzymes characterised earlier. The sequence of TaNPP includes that of a putative transmembrane domain, a characteristic of most NPPs. Both recombinant and native TaNPP partially occur as oligomeric proteins on SDS PAGE. Upon addition of DTT, both migrate as monomeric proteins. Part of the native wheat protein even occurs in its truncated form, thus lacking the transmembrane region. Out of a range of tested natural substrates, TaNPP had the highest affinity towards adenine containing nucleotides. While Michaelis-Menten kinetics were valid in the low substrate concentration range, at higher concentrations, they were no longer applicable. TaNPP shows no similarity to the recently characterised rice and barley enzymes and, is hence, one of the first characterised plant NPPs resembling mammalian NPPs.     

Field Validation of the Southern Rock Lobster Paralytic Shellfish Toxin Monitoring Program in Tasmania,Australia

Paralytic shellfish toxins (PST) are found in the hepatopancreas of Southern Rock Lobster Jasus edwardsii from the east coast of Tasmania in association with blooms of the toxic dinoflagellate Alexandrium catenella. Tasmania’s rock lobster fishery is one of the state’s most important wild capture fisheries, supporting a significant commercial industry (AUD 97M) and recreational fishing sector. A comprehensive 8 years of field data collected across multiple sites has allowed continued improvements to the risk management program protecting public health and market access for the Tasmanian lobster fishery. High variability was seen in toxin levels between individuals, sites, months, and years. The highest risk sites were those on the central east coast, with July to January identified as the most at-risk months. Relatively high uptake rates were observed (exponential rate of 2% per day), similar to filter-feeding mussels, and meant that lobster accumulated toxins quickly. Similarly, lobsters were relatively fast detoxifiers, losing up to 3% PST per day, following bloom demise. Mussel sentinel lines were effective in indicating a risk of elevated PST in lobster hepatopancreas, with annual baseline monitoring costing approximately 0.06% of the industry value. In addition, it was determined that if the mean hepatopancreas PST levels in five individual lobsters from a site were <0.22 mg STX equiv. kg⁻¹, there is a 97.5% probability that any lobster from that site would be below the bivalve maximum level of 0.8 mg STX equiv. kg⁻¹. The combination of using a sentinel species to identify risk areas and sampling five individual lobsters at a particular site, provides a cost-effective strategy for managing PST risk in the Tasmanian commercial lobster fishery.     

Investigation of Interspecies Interactions within Marine Micromonosporaceae Using an Improved Co-Culture Approach

With respect to bacterial natural products, a significant outcome of the genomic era was that the biosynthetic potential in many microorganisms surpassed the number of compounds isolated under standard laboratory growth conditions, particularly among certain members in the phylum Actinobacteria. Our group, as well as others, investigated interspecies interactions, via co-culture, as a technique to coax bacteria to produce novel natural products. While co-culture provides new opportunities, challenges exist and questions surrounding these methods remain unanswered. In marine bacteria, for example, how prevalent are interspecies interactions and how commonly do interactions result in novel natural products? In an attempt to begin to answer basic questions surrounding co-culture of marine microorganisms, we have tested both antibiotic activity-based and LC/MS-based methods to evaluate Micromonosporaceae secondary metabolite production in co-culture. Overall, our investigation of 65 Micromonosporaceae led to the identification of 12 Micromonosporaceae across three genera that produced unique metabolites in co-culture. Our results suggest that interspecies interactions were prevalent between marine Micromonosporaceae and marine mycolic acid-containing bacteria. Furthermore, our approach highlights a sensitive and rapid method for investigating interspecies interactions in search of novel antibiotics, secondary metabolites, and genes.     

Impact of compost and manure on the ripening of dredged sediments

Journal of Soils and Sediments - In low lying areas with dense networks of canals for land drainage, sediments accumulate in the waterways and have to be periodically dredged. These adjacent areas...