A Simple Method for Isolating DNA of High Yield and Quality from Cotton (shape Gossypium hirsutum L.) Leaves

An easy, reproducible and fast procedure to isolate DNA from cotton leaves is described. The addition of 0.5 M glucose in the extraction buffer avoids browning by polyphenolic compounds and improves the quality of DNA for molecular analysis. The DNA yield ranged between 150–400 mg per gram of fresh tissue. The DNA was suitable for digestion by restriction enzymes and amplificatiion by Taq DNA polymerase.     

Changes in plant species richness and productivity in response to decreased nitrogen inputs in grassland in southern England

Biomass production and plant species diversity in grassland in southern England was monitored before and after a change from conventional to organic farming. Our 18-year study, part of the UK's Environmental Change Network long-term monitoring programme, showed that the cessation of artificial fertiliser use on grassland after conversion to organic farming resulted in a decrease in biomass production and an increase in plant species richness. Grassland productivity decreased immediately after fertiliser application ceased, and after two years the annual total biomass production had fallen by over 50%. In the subsequent decade, total annual grassland productivity did not change significantly, and yields reached 31–66% of the levels recorded pre-management change. Plant species richness that had remained stable during the first 5 years of our study under conventional farming, increased by 300% over the following 13 years under organic farm management. We suggest that the change in productivity is due to the altered composition of species within the plots. In the first few years after the change in farming practice, high yielding, nitrogen-loving plants were outcompeted by lower yielding grasses and forbs, and these species remained in the plots in the following years. This study shows that grassland can be converted from an environment lacking in plant species diversity to a relatively species-rich pasture within 10–15 years, simply by stopping or suspending nitrogen additions. We demonstrate that the trade-off for increasing species richness is a decrease in productivity. Grassland in the UK is often not only managed from a conservation perspective, but to also produce a profitable yield. By considering the species composition and encouraging specific beneficial species such as legumes, it may be possible to improve biomass productivity and reduce the trade-off.     

The critical weed-free period in organically-grown winter wheat

Two experiments were conducted in central southern England between September 1994 and August 1996 to identify the critical weed-free period in organically grown winter wheat (Triticum aestivum, cv. Mercia). In competition with a mixed weed infestation of predominately Alopecurus myosuroides and Tripleurospermum inodorum it was found that wheat yield decreased as the duration of the weed-infested period increased and that the crop needed to be kept free of weeds from sowing in order to completely avoid any yield loss. Also, weeds emerging in the wheat crop (predominately T. inodorum) during the growing season had a significant and detrimental effect on yield. The existence of the critical period, therefore, depends on the imposition of an acceptable yield loss. If a 5% yield loss gives a marginal benefit compared with the cost of weed control, the critical period will begin at 506°C days after sowing (November) and end at 1023°C days after sowing (February). This information could be used by farmers to target mechanical weeding operations to control weeds at a time that will have maximum benefit to the crop.     

Antibacterial Agents in Mediterranean Finfish Farming: A Synopsis of Drug Pharmacokinetics in Important Euryhaline Fish Species and Possible Environmental Implications

The literature pertaining to the use of registered antibacterial agents in Mediterranean finfish farming is reviewed, with an emphasis on the Greek fish-farming industry. This review provides a scientific resource dedicated to the design of future antibacterial dosing regimes in Mediterranean fish farming, where insufficient supporting information is currently available. This paper addresses the paucity in knowledge concerning pharmacokinetics and the efficacy and environmental impact of commonly used antibacterials needed to direct future research and promote good practices in the euryhaline fish farming industry. Several registered antibacterials are currently available for combating bacterial infections, including tetracyclines, (fluoro) quinolones, potentiated sulfa, penicillin and chloramphenicol derivatives. Based on the available data, oxytetracycline (OTC) and quinolone drugs (oxolinic acid – OA and flumequine – FLU) are the most widely used in Mediterranean aquaculture. As a result these drugs have received the most extensive studies, whereas, there is considerable paucity of reliable data on pharmacokinetic and the depletion characteristics of other drugs used, particularly potentiated sulfa, penicillin derivatives and florfenicol. We find there is incomplete data on drug efficacy and minimum inhibitory concentrations (MIC) for common antibacterials used against the major bacterial pathogens of Mediterranean fish species. Furthermore, a considerable lack of data on environmental drug concentrations around Mediterranean fish farms was also identified, highlighting the need for more extensive environmental studies to monitor contamination in environmental components i.e., water and sediment, and in non-target species (flora and fauna). Prudent selection and use of antibacterials can encourage lower dosage applications, enhance treatment efficacy, and help to minimize contamination of the environment. Selection of readily bioavailable drugs which have low environmental persistence, low aquatic toxicity and high antibacterial efficacy is advised, to reduce potential losses to the environment and associated toxic effects on target species and the development of bacterial resistance. Lack of present data made it impossible to provide thorough and accurate guidance on selection and use of antibacterials and approaches for minimizing environmental impacts for the treatment of major euryhaline aquaculture species.     

Milk: the new white gold? Milk production options for smallholder farmers in Southern Mali

Until the turn of the century, farmers in West Africa considered cotton to be the ‘white gold’ for their livelihoods. Large fluctuations in cotton prices have led farmers to innovate into other business including dairy. Yet the productivity of cows fed traditional diets is very poor, especially during the long dry season. This study combines earlier published results of farmer participatory experiments with simulation modelling to evaluate the lifetime productivity of cows under varying feeding strategies and the resulting economic performance at farm level. We compared the profitability of cotton production to the innovation of dairy. The results show that milk production of the West African Méré breed could be expanded if cows are supplemented and kept stall-fed during the dry season. This option seems to be profitable for better-off farmers, but whether dairy will replace (some of) the role of cotton as the white gold for these smallholder farmers will depend on the cross price elasticity of cotton and milk. Farmers may (partly) replace cotton production for fodder production to produce milk if the price of cotton remains poor (below US$0.35/kg) and the milk price relatively strong (higher than US$0.38/kg). Price ratios need to remain stable over several seasons given the investments required for a change in production strategy. Furthermore, farmers will only seize the opportunity to engage in dairy if marketing infrastructure and milk markets are further developed.     

Response to drought among farmers and herders in southern Kajiado District,Kenya

From 1972 to 1976 rainfall in Kajiado District of Kenya was below normal. The capacity of the farming and herding systems to cope with the consequent reduction in production is discussed within a context of changing land-use patterns and altered resource availability. It is concluded that land-use planning to allocate the available land and water resources and to promote off-farm employment is required to reduce the vulnerability of the population to future drought conditions.     

Developmental biochemistry of cottonseed embryogenesis and germination. XIX. Sequences and genomic organization of the α globulin (vicilin) genes of cottonseed

The globulin storage protein genes of cotton are found to exist as gene tandems that contain a gene from each of the 2 globulin subfamilies separated by a spacer region of about 2700 or 3400 base pairs. Three different tandems have been identified by restriction endonuclease mapping of genomic DNA. A cDNA that is different from the genes of the tandems in map sites and/or in nucleotide sequence indicates that a fourth tandem probably exists in the cotton genome. Since the species of cotton used here (Gossypium hirsutum) is an amphidiploid, it is likely that two of the tandems are contributed from each genome.Considerable divergence in nucleotide sequence (18%) and in derived amino acid sequence (28%) is found when the 2 genes of a sequenced tandem are compared. The sequence of the cDNA closely resembles one of the genes in the tandem showing only a 4% divergence in nucleotides and a 4.2% divergence in amino acids. Thus the 2 genes of each tandem represent a relatively ancient gene duplication that has given rise to the two globulin subfamilies of cotton. Only one subfamily has a glycosylation site and the glycosylation of its derived proteins gives rise to the 2 molecular weight sets of globulins seen on gel electrophoresis.Other basic features of these genes and their derived proteins are presented.