Stages of embryonic development and changes in enzyme activities in embryogenesis of turbot (Scophthalmus maximus L.)

The early development of turbot (Scophthalmus maximus) from fertilization to hatching was described. Hatching occurred at 108 h post-fertilization (hpf) in 14 °C. Yolk syncytial layer and blastocoel formed at morula stage and low stage, respectively. Neural rod derived from the ectoderm appeared and the first somite formed in the middle of the embryonic body at 90 % epiboly stage, and notochord primordium formed at complete epiboly stage. Kupffer’s vesicle appeared at 59 h 35 min hpf and degenerated at 89 hpf. At 72 hpf, the digestive tract formed in the ventral side of the embryonic body, and the posterior digestive tract of embryo was ciliated at 89 hpf. Enzymes play a key role in the catabolism of yolk during embryogenesis of fishes. In this study, the main enzymes alkaline phosphatase (AP), leucine aminopeptidase N (LAP), pepsin, trypsin and Leucine-alanine peptidase (Leu-ala) were all observed in unfertilized eggs and embryo of S. maximus, but amylase was not detected, speculating that amino acids appear to be the main energy substrate during embryonic development of S. maximus, while carbohydrates is less essential. AP reached the lowest value at the gastrula stage and then increased rapidly reaching the highest value at hatching. LAP showed the highest value in unfertilized eggs and kept on decreasing until the blastula stage with the lowest value and then increased at the gastrula stage, followed by a gradual decline thereafter. Trypsin reached the lowest value at the blastula stage and then fluctuated with the maximal value at hatching. Pepsin reached the highest and the lowest values at the unfertilized eggs and the cleavage stage, respectively, but disappeared at hatching. Leu-ala had the maximum activity at the blastula stage and then declined to the minimum at the gastrula stage followed by a gradual increase thereafter.     

Dietary phosphorus prevents oxidative damage and increases antioxidant enzyme activities in intestine and hepatopancreas of juvenile Jian carp

This study was conducted to investigate the effect of dietary phosphorus on the intestine and hepatopancreas antioxidant capacity of juvenile Jian carp (Cyprinus carpio var. Jian). Jian carp, with an average initial weight of 7.17 ± 0.01 g, were fed with diets containing graded concentrations of available phosphorus, namely 1.7 (control), 3.6, 5.5, 7.3, 9.2 and 11.0 g kg^?1 diet for 9 weeks. Results showed that, in intestine and hepatopancreas, content of malondialdehyde (MDA), protein carbonyl (PC) and glutathione (GSH), capacity of anti‐superoxide anion (ASA) and anti‐hydroxyl radical (AHR), and glutathione reductase (GR), catalase (CAT), glutathione S‐transferase (GST), superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities were significantly affected by dietary phosphorus levels (P < 0.05). Regression analysis showed that significant quadratic responses occurred in MDA content and ASA, GST, GPx and AHR activities in intestine, GSH content and CAT and SOD activities in hepatopancreas (P < 0.05). These results indicate that optimal level of dietary phosphorus prevented oxidative damage and increased antioxidant enzyme activities in the intestine and hepatopancreas of juvenile Jian carp. The phosphorus requirement estimated from MDA using quadratic regression analysis was 5.7 g kg^?1 diet.     

竹纤维复合材料的界面连接:用壳聚糖进行表面处理

本研究利用系统地实验性结果描述了竹纤维的动态润湿性能,并通过润湿分子动力学理论进行了分析。结果表明,竹纤维的表面能够对润湿分析表现良好可控性。通过这种方式,利用不同的热塑性塑料对竹纤维的表面自由能的进行附着力的研究,可以得到界面相互作用的有价值的信息。为了提高竹纤维的相容性,本研究利用壳聚糖进行涂膜,并且使用吊片法(Wilhelmy technique)通过接触角测量对这种处理方法的效果进行了评估,利用酸碱理论计算表面自由能的分量。这些值是用来推算粘附力的理论上产生的效果。对于各种热塑性基质(聚偏氟乙烯,聚丙烯和马来酸酐接枝聚丙烯)进行润湿行为后的特征,本研究利用原子力显微镜观察其表面微形貌,用X射线光单子能谱(XPS)确定其表面的化学成分。此外,本研究还制备了单向竹纤维复合材料,以通过3点弯曲试验实现对因粘附引起的纤维改性效果的直接测量。     

Quantitative trait loci for high-temperature adult-plant and slow-rusting resistance to Puccinia striiformis f. sp. tritici in wheat cultivars

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the most damaging diseases of wheat (Triticum aestivum) globally. High-temperature adult-plant resistance (HTAPR) and slow-rusting have great potential for sustainable management of the disease. The wheat cultivars Luke and Aquileja have been previously reported to possess HTAPR and slow-rusting to stripe rust, respectively. Aquileja displayed less number of stripes per unit leaf area than Luke, while Luke showed lower infection type than Aquileja at adult-plant stages of growth under high-temperature conditions. The objectives of this study were to confirm the resistances and to map the resistance genes in Luke and Aquileja. Luke was crossed with Aquileja, and 326 of the F(2) plants were genotyped using 282 microsatellite primer pairs. These F(2) plants and their derived F(3) families were evaluated for resistance to stripe rust by inoculation in the fields and greenhouses of high- and low-temperatures. Infection type was recorded for both seedlings and adult plants, and stripe number was recorded for adult plants only. Two quantitative trait loci (QTL) were identified, on the short arm of chromosome 2B, to be significantly associated with infection type at adult-plant stages in the fields and in the high-temperature greenhouse. The locus distal to centromere, referred to as QYrlu.cau-2BS1, and the locus proximal to centromere, referred to as QYrlu.cau-2BS2, were separated by a genetic distance of about 23 cM. QYrlu.cau-2BS1 was flanked by the microsatellite markers Xwmc154 and Xgwm148, and QYrlu.cau-2BS2 was flanked by Xgwm148 and Xabrc167. QYrlu.cau-2BS1 and QYrlu.cau-2BS2 explained up to 36.6 and 41.5% of the phenotypic variation of infection type, respectively, and up to 78.1% collectively. No significant interaction between the two loci was detected. Another QTL, referred to as QYraq.cau-2BL, was detected on the long arm of chromosome 2B to be significantly associated with stripe number. QYraq.cau-2BL was flanked by the microsatellite markers Xwmc175 and Xwmc332, and it explained up to 61.5% of the phenotypic variation of stripe number. It is possible that these three QTL are previously unmapped loci for resistance to stripe rust.     

Strategies to prevent spread of Leptosphaeria maculans (phoma stem canker) onto oilseed rape crops in China; costs and benefits

Field experiments in Europe have shown that Chinese cultivars of winter oilseed rape ( Brassica napus ) are very susceptible to the pathogen Leptosphaeria maculans (cause of phoma stem canker). Climatic and agronomic conditions in China are suitable for L. maculans since the closely related but less damaging pathogen L. biglobosa occurs on the winter and spring oilseed rape crops there. Major gene resistance to L. maculans is not durable; when introduced into commercial oilseed rape cultivars it is rapidly rendered ineffective by changes in the pathogen population. The threat to Chinese oilseed rape production from L. maculans is illustrated by the way in which L. maculans has spread into other areas of the world where previously only L. biglobosa was present, such as Canada and Poland. Models were developed to describe the spread (in space and time) of L. maculans across Alberta province, Canada, based on survey data collected over a 15-year period. These models were used to estimate the potential spread of L. maculans across the Yangtze river oilseed rape growing areas of China and its associated costs. Short-term strategies to prevent occurrence of severe phoma stem canker epidemics in China include training of extension workers to recognise symptoms of the disease and use of PCR-based diagnostics to detect the pathogen on imported seed. Long-term strategies include the introduction of durable resistance to L. maculans into Chinese oilseed rape cultivars as a component of an integrated disease management programme. The costs of such strategies in relation to costs of a phoma stem canker epidemic are discussed.     

Effects of dietary biotin supplement on growth,body composition,intestinal enzyme activities and microbiota of juvenile Jian carp (Cyprinus carpio var. Jian)

A total of 1400 juvenile Jian carp (Cyprinus carpio var. Jian) (7.72 ± 0.02 g) were fed seven purified diets containing 0.010 (basal diet), 0.028, 0.054, 0.151, 0.330, 1.540 and 2.680 mg biotin kg^?1 for 63 days to investigate the effects of biotin on growth, body composition, intestinal enzyme activities and microbiota. Specific growth rate (SGR), feed intake, feed efficiency and protein retention value were the highest when dietary biotin level was 0.151 mg kg^?1 diet. Crude protein, lipid and ash content of fish carcass improved with increasing dietary biotin levels up to 0.054, 0.151 and 0.028 mg kg^?1 diet, respectively (P < 0.05). Intestinal folds height, trypsin, chymotrypsin, lipase, amylase, alkaline phosphatase, Na⁺, K⁺‐ATPase, γ‐glutamyl transpeptidase and creatinekinase activities increased with dietary biotin levels up to 0.151–0.330 mg kg^?1 diet (P < 0.05). Intestinal Aeromonas and Escherichia coli significantly decreased with increasing dietary biotin up to 0.151 mg kg^?1 diet, while Lactobacillus and Bacillus significantly increased with dietary biotin levels up to 0.054 and 0.151 mg kg^?1 diet, respectively. In conclusion, biotin could improve digestive and absorptive ability of fish, and the dietary biotin requirement for SGR of juvenile Jian carp (7.72–32.67 g) was 0.15 mg kg^?1 diet.