Decomposition processes in coastal lagoons and their implications for the assessment of ecological health

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Multilocus sequence analysis supports a low genetic diversity among ‘<Emphasis Type="Italic">Candidatus</Emphasis> Phytoplasma australasia’ related strains infecting vegetable crops and periwinkle in Egypt

‘Candidatus Phytoplasma australasia’ causes important damages to the Egyptian vegetable crop production. A prerequisite for controlling the different diseases it causes to eggplant, tomato and squash, is to trace its propagation pathways. To allow the differentiation of ‘Ca. P. australasia’ strains, a multilocus sequence analysis protocol was developed. Four conserved phytoplama genes namely tuf, secY, dnaK and dppA, were selected among the CDS of a ‘Ca. P. aurantifolia’ genome draft. The corresponding genes were PCR amplified from tomato, eggplant and squash collected in 2010 from the governorates Sharkia, Elmynia and Beni sueif, as well as from Catharanthus roseus periwinkles collected in 2013 from Kafrelsheikh governorate. Sequence comparisons showed no diversity among the Egyptian isolates of ‘Ca. P. australasia’ that also constitute a distinct cluster within the 16SrII-D taxonomic subgroup. This low diversity supports a common epidemiology for the different diseases affecting vegetable crops and periwinkle in Egypt and suggests that future investigations on insect vector should focus on polyphagous leafhoppers.     

Availability of minerals in rendered meat and bone meal for Nile tilapia: Preliminary observations

A digestibility trial was conducted with 180 Nile tilapia (32.65 ± 4.52 g) fed a reference diet containing 350 g/kg crude protein and 4,500 kcal/kg gross energy. Five different meat and bone meals (MBMs) were evaluated. The test diets compound by 70% of reference diet and 30% of each MBM were elaborated and classified according to ash content: MBM‐430, MBM‐400, MBM‐370, MBM‐340 and MBM‐310. The apparent availability coefficient (AAC) of minerals and the apparent digestibility coefficient (ADC) of dry matter (DM) were subjected to one‐way analysis of variance (p < .05). Differences among ADC and AAC were determined by Tukey's multiple range test (p < .05). When appropriate, a polynomial regression analysis was performed. Linear correlation analyses between MBM chemical composition and the AAC and ADC were performed (p < .01). Higher values of ADC_DM, AAC_Ca and AAC_P were observed in MBM‐310, while low values were observed in MBM‐430. Quadratic effects of ash, P and Ca contents on AAC_Ca, AAC_P and ADC_DM were observed. The AAC_Ca, AAC_P and ADC_DM indicated a negative correlation with ash, P and Ca contents. MBM‐310 exhibited the highest mineral AAC, which could be used as a mineral source for Nile tilapia.     

Performance of <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis> postlarvae reared in indoor nursery tanks under biofloc conditions at different salinities and zero-water exchange

Shrimp farming at low salinity is a trend that will continue to grow globally. Performance of Litopenaeus vannamei postlarvae in the nursery at different salinities with a biofloc technology (BFT) system needs to be explored further, as the nursery is currently used as a transitional stage between the hatchery and grow-out ponds. Hence, this study evaluated the effect of seven salinity levels (2, 4, 8, 12, 16, 25, and 35 ‰) on the performance of L. vannamei postlarvae reared with a BFT system and zero-water exchange at 2000 org/m³. Additionally, this study evaluated the water quality of all salinity treatments. After 28 days of culture, the findings showed that, under biofloc conditions, salinity affected the performance of some variables of water quality in some cases, but only the combination of a high nitrite-N concentration (>4 mg/l) and low salinity (2 and 4 ‰) caused up to 100 % shrimp mortality in the first 2 weeks. In the rest of the treatments (8, 12, 16, 25, and 35  ‰), shrimp survival was >72 %. Shrimp mortality was affected by salinity, especially when it decreased from 35–25–16 to 12 and 8 ‰. The organisms reared at low salinities presented lower final weights and specific growth rate than those reared at higher salinities. An inverse relationship was shown between the ion concentration and the final weight of shrimp.     

Latex proteins from the plant Calotropis procera are partially digested upon in vitro enzymatic action and are not immunologically detected in fecal material

Soluble proteins from the latex of Calotropis procera (LP) were investigated in vitro and in vivo for digestibility as the latex has previously been shown to produce considerable toxic effects on animals. The latex is also an important biologically active compound that displays antiinflammatory and antidiarrhea properties. The proteins were digested by the action of trypsin, pepsin or chemotrypsin as revealed by gel filtration and SDS-PAGE analysis. Furthermore, the full LP digestion was easily achieved by protease treatment. Rabbit polyclonal antibodies raised against LP failed to detect cross-reactive molecules in fecal material of experimental rats following 35 consecutive days of LP consumption in water. Similar patterns of electrophoresis were observed for the negligible amounts of protein observed in the fecal extracts of control and test animals. No death or toxic effects were observed among animals. Taken together these results suggest that harmful and toxic effects on animals of the latex from C. procera are present in its rubber and low molecular weight fractions rather than its protein content.     

Distribution and composition of phytosterols and steryl ferulates in wheat grain and bran fractions

Phytosterols and steryl ferulates are bioactive compounds accumulating in the bran and germ of wheat. However, little is known regarding their localisation and composition in the bran layers of the kernel. The aim of this study was to determine the distribution of phytosterols and steryl ferulates in the wheat grain and in the different layers of bran. The wheat fractions, produced by conventional debranning, aleurone separation and a novel electrostatic process, were analysed for phytosterol contents using GC–FID and for steryl ferulate contents using HPLC–UV. The compounds were identified by GC– and LC–MS. Phytosterols and steryl ferulates were concentrated in the bran layers. The steryl ferulates were accumulated in the intermediate layers, whereas the phytosterols were more evenly distributed in the intermediate layers and aleurone cell contents. The phytosterol composition varied within the wheat kernel, while the steryl ferulate composition was similar in different fractions. Sitosterol and campestanyl ferulate were the main compounds. The highest levels of phytosterols (up to 2117 μg/g) and steryl ferulates (up to 703 μg/g) were found in the pearling, aleurone and certain bran fractions. The phytosterol-rich fractions could be utilised in cereal foods to enhance the intake of health-promoting compounds from natural sources.     

Path analysis for selection of drought tolerant sugarcane genotypes through physiological components

Water deficit is among the main environmental factors limiting agricultural productivity of sugarcane in Northeast Brazil by affecting virtually every aspect of plant growth, with consequent reduction of the agro-industrial productivity of this crop. This study aimed to use path analysis to evaluate the physiological components of sugarcane under two water conditions, with photosynthesis as the basic variable, in order to obtain subsidies that can help the genetic breeding of this crop by selection of superior clones with drought tolerance. The experiment was carried out in a greenhouse with a completely randomized experimental design, 4 × 2 factorial arrangements (four sugarcane genotypes × two soil moisture regimes: control, with 80-100% available water and stressed, with 0-20% water available) and with four replications. Each plot consisted of one pot with 12 kg of substrate containing one plant. Treatments were maintained at a humidity close to field capacity with daily replacement of the evapotranspired water with a water supply for 66 days of cultivation for treatments under stress. Evaluations were conducted on the fourth day after severe water stress at 70 days of cultivation. Data from nine physiological variables were considered, with six of these being used in the model after exclusion of those that were contributing to multicollinearity. Variables used in path analysis were enough to explain the variation found in photosynthesis under both water conditions. Stomatal conductance, transpiration and the SPAD index should be considered as a priority in breeding programs for sugarcane aiming to get more productive and tolerant genotypes to water stress, and selection indexes should be used with due consideration of these variables to promote gains in photosynthesis.     

Delaying weed adaptation to herbicide by environmental heterogeneity: a simulation approach

BACKGROUND: Environmental heterogeneity in space or time can drive the evolutionary trajectory of an adaptive trait. This concept could be of practical significance in pesticide resistance management that aims to delay the evolution of a resistance allele. Using a population genetics model, the dynamics of herbicide resistance in a weed species was simulated in a heterogeneous environment with alternation of two unrelated herbicides in time, in space or in both time and space. The level of the environmental heterogeneity (habitat grain) was simulated by a variation in the size of the herbicide-treated areas. RESULTS: The model confirms that several strategies based on habitat heterogeneity efficiently slow down and even prevent resistance evolution. For a recessive resistant trait in outcrossing species, a medium level of environmental heterogeneity (intermediate habitat grain) was found to be the best for delaying herbicide resistance, as previously observed for insecticide resistance management. In selfing species or for a dominant resistant trait in outcrossing species, a low level of environmental heterogeneity (coarse-grained habitat) was more efficient in delaying resistance evolution when heterogeneity in both space and time were considered. CONCLUSION: This model suggests that the choice of optimal tactics for delaying herbicide resistance by enhanced heterogeneity in space or time firstly depends on the interactions between the breeding system and the dominance of the resistance allele in the presence of herbicide, then on the value of the fitness cost and lastly on the dominance of this fitness cost.