Quantification of dwarfing effect of different rootstocks in ‘Picual’ olive cultivar using UAV-photogrammetry

Precision Agriculture - Hedgerow orchard is an olive growing system where trees are planted at a super high-density higher than 20-fold (i.e., 1200–2500 trees ha?1) compared to the...     

渭南市玉米适宜籽粒直收品种筛选试验研究

研究旨在筛选渭南地区适用的机械化籽粒直收玉米新品种。试验共征集比较10个玉米品种的农艺性状、产量指标。结果表明,在“陕单620”、“陕单650”、“迪卡517”玉米品种表现出矮秆、穗位整齐度高、耐密、茎秆强度强、抗倒、成熟期籽粒水分含量低、高产、生育期短等宜机收的特性,建议在关中灌区夏玉米种植区推广。     

橡胶树人工林土壤腐殖质组成与土壤酸度关系研究

对海南省儋州市橡胶园土壤腐殖质组成与土壤酸度含量进行研究,结果表明,该植胶区橡胶林0～40cm土壤腐殖质组成含碳量大小依次为富里酸、胡敏素、胡敏酸;土壤活性酸度范围在4.32～5.56之间,土壤属于酸性和强酸性,且不同母岩和地形对土壤潜性酸度影响不同.在简单相关分析中富里酸与土壤水解酸度呈极显著正相关关系(r=0.58),而土壤胡敏酸与pH显著正相关(r=0.41)、与水解酸度显著负相关(r=-0.39)、与交换性酸度显著负相关(r=-0.48).运用典型相关分析研究腐殖质组成和土壤酸度之间的关系,发现土壤腐殖酸是水解酸度的主要影响因素,而胡敏酸和胡敏素与土壤交换性酸度关系密切.     

Influence of circulating GH levels on GH-binding capacity measurements in the hepatic membrane of rainbow trout (Oncorhynchus mykiss): importance of normalization of results

In fish, regulation of the growth hormone (GH) receptor has been mainly analyzed by binding studies, with some discrepancies in the results. The present work aims at determining whether circulating GH levels influence the measurement of hepatic GH-binding capacities. To do this, the effectiveness of the dissociation of the GH/GH receptor (GHR) complex by an MgCl₂ treatment was assessed in rainbow trout, and data on GH-binding capacities under various physiological conditions were studied using different means of expression. Our results reveal that MgCl₂ treatment dissociated the liver GH/GHR complex formed under in vitro conditions (85 ± 23 vs. 361 ± 16 fmol/g of liver; p<0.001) but not in vivo, showing such treatment in trout is not applicable. A comparison of fasted (3 weeks) and fed fish revealed that GH-binding capacities, expressed as femtomoles per milligram protein or femtomoles per gram of liver, were similar in both fed and fasted fish. However, when changes in liver and body size were taken into account, the total GH-binding capacities were lower in the fasted fish (0.026 ± 0.006 vs. 0.062 ± 0.009 fmol/cm³ liver; p<0.05). One day after hypophysectomy or GH injection, changes in the plasma GH levels increased or decreased GH-binding capacities, respectively. Five days later, GH-binding capacities increased in GH-injected fish (527 ± 38 vs. 399 ± 38 fmol/g liver; p<0.01). Our interpretation is that acute treatment modified GH-binding capacities through receptor occupancy and that GH stimulated the synthesis of its own receptor. On the other hand, long-term treatment through successive injections of GH lowered the total binding capacities (approx. 40%), which could result from receptor occupancy. We conclude that circulating GH levels strongly influence the measurement of GH-binding capacities in the liver, thereby limiting interpretation of the binding data and preventing accurate conclusions to be drawn on GHR regulation.     

Evidence of hybridization between Yaqui catfish Ictalurus pricei (Rutter, 1896) and channel catfish Ictalurus punctatus (Rafinesque, 1818) in north-west México revealed by analysis of mitochondrial and nuclear genes

1. The Yaqui catfish, Ictalurus pricei, is the only native ictalurid species described from north-west México and south-west USA. It is an endangered species owing to the decline and loss of most of its historical populations, mainly because of competition and hybridization with the non-native channel catfish, Ictalurus punctatus. The Arroyo Cajón Bonito is one of the few remnant populations of Yaqui catfish in the Yaqui River basin, and it is threatened by the presence of channel catfish that escaped from private culture facilities.
2. Phylogenetic analysis of two mitochondrial and two nuclear genes was used to detect evidence of hybridization with channel catfish in a collection of 20 catfish from Arroyo Cajón Bonito. Fourteen putatively pure Yaqui catfishes, five hybrids and one channel catfish were detected.
3. This study further highlights hybridization between channel and Yaqui catfish as the main threat to the remaining Yaqui catfish populations. We recommend urgent evaluation of the remnant populations of native catfish elsewhere and their current conservation status.

     

约氏笛鲷自然群体遗传多样性的RAPD分析

约氏笛鲷 (Lutjanusjohni)样品 10尾 ,取自湛江近海自然种群。从 12 0个随机引物中筛选出 16个引物 ,采用RAPD技术对其进行分析。结果表明 ,16个引物共检测到 2 15个位点 ,其中多态位点比例 (P)为 78.6 0 % ,遗传相似系数 (S)为 0 .72 70 ,遗传距离 (D)为 0 .2 730 ,遗传多样性指数 (H)为 0 .2 0 85。目前湛江近海约氏笛鲷自然群体种质资源仍然维持在良好水平 ,捕捞尚未对其造成明显影响     

Nitrogen utilisation and ureogenesis as affected by dietary nucleic acid in rainbow trout (Oncorhynchus mykiss) and turbot (Psetta maxima)

We evaluated the influence of dietary nucleic acid (NA) supplied either as an RNA extract (RNA) or as brewer's yeast (BY) on nitrogen (N) utilisation, N excretion and ureogenesis in a freshwater teleost, the rainbow trout (Oncorhynchus mykiss) and a marine teleost, the turbot (Psetta maxima). Five diets containing two levels of NA or BY were formulated for each species, and fed to juvenile rainbow trout (initial body weight (IBW): 21.7 g) and turbot (IBW: 11.8 g) over 8–10 weeks. Besides growth and N utilisation, we monitored total ammonia-N and urea-N excretion rates and measured the activities of selected enzymes (glutamate dehydrogenase, ornithine carbamoyltransferase, arginase and uricase). There was no clear N sparing effect of dietary NA or BY supplementations in either species. Feeding diets containing the RNA extract led to an almost two-fold increase in postprandial plasma urea-N and uric acid concentrations and in urea-N excretion rates. Glutamate dehydrogenase and arginase activities were decreased in fish fed NA supplemented diets. Uricase activities were inversely related to dietary NA levels. Data on N excretion and enzyme activities clearly suggest that ureogenesis is influenced by dietary NA in both species. This revised version was published online in July 2006 with corrections to the Cover Date.     

Biological and technical evaluation of the potential of marine and anadromous fish species for cold-water mariculture

Concern about the overexploitation of wild aquatic resources, the slow recovery of the groundfish fisheries and the need to encourage the diversification of the mariculture industry of the province of Quebec (Canada) all provided strong incentive to explore the potential of a wide selection of marine and anadromous fish species for cold‐water mariculture. Starting from a list of over 45 indigenous fish species of potential commercial interest, a biotechnical review was initiated. Technical sheets for each species were produced and aquaculture‐based selection criteria covering three aquaculture approaches of development (complete life cycle, on‐growing and stock enhancement) were examined. Species were ranked according to their degree of suitability for the given biological parameters. The final classification analysis within the complete life cycle production strategy positioned the Atlantic wolffish as the top candidate species (91%) followed by the spotted wolffish and Arctic charr (87%). Growth rate, optimal growth temperature, duration of the weaning period, minimal lethal temperature, larval size and feed requirements were the determining criteria. The on‐growing scenario final results ranked Arctic charr first (84%) followed by Atlantic cod (79%) and Atlantic halibut (74%) mostly owing to their growth rate at low temperature and optimal growth temperature criteria. Stock enhancement programmes should concentrate their efforts on the striped bass (56%), the haddock (54%) and the Atlantic sturgeon (34%) based on their growth rate, fishery status, landing price and the availability of impact studies.     

Use of GIS and machine learning to predict disease in shrimp farmed on the east coast of the Mekong Delta,Vietnam

Diseases in shrimp farms in the Mekong Delta of Vietnam cause significant crop losses and are therefore of great concern to producers. Once a pond becomes infected, it is difficult to prevent spread of the disease to nearby shrimp farming areas. Thus, predicting the occurrence of disease is an essential part of reducing the risk for shrimp farmers. In this study, we applied an integrated geographic information system and machine learning system to predict three serious diseases of shrimp, namely, acute hepatopancreatic necrosis, white spot syndrome disease, and Enterocytozoon hepatopenaei infection, based on data collected from shrimp farms in the Tra Vinh, Bac Lieu, Soc Trang, and Ca Mau provinces of Vietnam. We first constructed a map showing the distribution of these diseases using the locations of affected farms, and then we conducted spatial analysis to acquire the geographical features of the affected locations. This latter information was combined with environmental factors and clinical signs to form the set of independent variables affecting the outbreak of diseases. The neural network model outperformed the logistic regression, random forest, and gradient boosting methods in terms of predicting infection to estimate the probability of disease occurrence in farmed areas. Acute hepatopancreatic necrosis disease infected farms downstream of the Co Chien and Hau Rivers of Tra Vinh and west of Ca Mau. Enterocytozoon hepatopenaei infection is distributed in Soc Trang Province, while white spot syndrome virus has spread to the coastal districts of Soc Trang and Bac Lieu Provinces, where it is highly associated to water from a complex canal system.

     

几种合成纤维渔网结牢度试验

由于合成纤维弹性较大、表面光滑,打结后结不易牢固。渔具自从使用合成纤维材料以来,网结的车度或网结的稳定性引起人们的关注。国外学者G.klust(1982),A.von.Brandt(1962)和本多胜司(1980)在他们各自的著作中,对结牢度的试验研究略有介绍,大致可归纳为三种情况:1)当网结受拉伸