Biochemical Changes in Freshwater Prawn Macrobrachium rosenbergii During Larval Development

Abstract.— Quantitative changes in the protein, lipid and carbohydrate were studied in the early larval stages of developing freshwater prawn Macrobrachium rosenbergii reared under fed and starved conditions to understand the relative importance of these nutrients in energy metabolism of the growing larvae. Larvae obtained from several females were stocked into three 250-L tanks at a density of 30 larvae/L. The feeding regime consisted of newly hatched Artemia nauplii. Protein was always the major organic constituent followed by lipids and then carbohydrates of both fed and starved larvae. Protein levels of both fed and starved larvae increased during development, suggesting an important role in morphogenesis. The decline of lipid during the larval growth that was more rapid for starved larvae, suggests a probable utilization of lipid as the major metabolic source of energy. Carbohydrates formed less than 5 and 2.4% of the larval dry weight of fed and starved larvae, respectively, suggesting their limited role in larval metabolism.     

“WaterMan”: an on-farm water management game with heuristic capabilities

A modern computer-based simulation tool (WaterMan) in the form of a game for on-farm water management was developed for application in training events for farmers, students, and irrigators. The WaterMan game utilizes an interactive framework, thereby allowing the user to develop scenarios and test alternatives in a convenient, risk-free environment. It includes a comprehensive soil water and salt balance calculation algorithm. It also employs heuristic capabilities for modeling all of the important aspects of on-farm water management, and to provide quantitative performance evaluations and practical water management advice to the trainees. Random events (both favorable and unfavorable) and different strategic decisions are included in the game for more realism and to provide an appropriate level of challenge according to player performance. Thus, the ability to anticipate the player skill level, and to reply with random events appropriate to the anticipated level, is provided by the heuristic capabilities used in the software. These heuristic features were developed based on a combination of two artificial intelligence approaches: (1) a pattern recognition approach and (2) reinforcement learning based on a Markov decision processes approach, specifically the Q-learning method. These two approaches were combined in a new way to account for the difference in the effect of actions taken by the player and action taken by the system in the game world. The reward function for the Q-learning method was modified to reflect the suggested classification of the WaterMan game as what is referred to as a partially competitive and partially cooperative game.     

Alleviation of alternate bearing phenomenon in mango (Mangifera indica L.) trees using boron and nitrogen fertilization

Abstract

This investigation was conducted during two successive seasons (2014/2015) and (2015/2016) using 15?years old productive mango (Mangifera indica) trees cv. Zebda. The trees were grown at AlMalak Valley Farm, El-Sharkeya Governorate- Egypt (30–51° North; 32–53° East). Trees were planted 8?×?8 meter within and between rows in sandy soil under drip irrigation system using the Nile water. The objective of this study is to alleviate alternate bearing in cv. Zebda using mineral nutrients (nitrogen in the on year and boron in the off year). Treatments included three concentrations of nitrogen (1000, 1250, 1500?g/tree/year) and three concentrations of boron (0.0, 250, 500?mg L^?1). Nitrogen was applied to the soil as ammonium sulfate and boron was applied as foliar spray of boric acid. The extra amount of nitrogen fertilizer (250 and 500?g N/tree) was applied at three installments in (May, June and July). Treatment was arranged in a factorial Completely Randomized Block Design with three replicates for each treatment. Results show that the on-year nitrogen fertilization significantly increased mango tree vegetative growth (number of shoot/branch, shoot length, shoot thickness, number of leaves/meter and leaf area) and yield. The average yield in the on year is 85.5?kg/tree at 1250?g N/tree but 67.4?Kilogram/tree at 1000?g N/tree (the control treatment). While in the off year boron foliar application resulted in a significant increase in flowering, initial fruit set, final fruit set and fruit yield. The average yield in the off year is 47?kg/tree at 250?mg L^?1 boron but 9?kg/tree at 0.0?mg L^?1 boron rate (the control treatment).The interaction treatment of 250?mg L^?1 boron + 1500?g nitrogen/tree is the best treatment as it resulted in the highest values for all the tested parameters. The average yield of this treatment is 53.5?kg/tree. This treatment helps alleviate alternate bearing phenomenon by 41% and obtain the highest economic yield in the off-year, i.e. increased yield by 5.9 fold.     

Detection,isolation and characterization of cowpea mosaic virus in Egypt

Journal of Plant Diseases and Protection - Cowpea mosaic virus is among the most economically important viruses infecting cowpea. Incidence of infection was assessed in two governorates in Egypt,...     

乌鲁木齐地区不同生境土壤捕食性螨类群落结构及其多样性研究

[目的]研究土壤捕食性螨类群落结构及其多样性特征,为开发利用及保护乌鲁木齐地区农林害虫捕食性天敌资源提供科学依据.[方法]采用塔氏( Tullgren)分离法和群落多样性分析方法对该区不同生境土壤捕食性螨类资源的群落结构、多样性及其季节动态变化进行比较分析.[结果]乌鲁木齐市不同生境土壤农林害虫捕食性螨类3643只,分别隶属于2目21科38属.其中前气门目螨类有5科11属,中气门目螨类有16科27属,其中优势类群为美绥螨属Ameroseius、囊螨属Asca、真长须螨属Eustigmaeus和表刻螨属Epicrius 等四类,占总捕获量的61.57;.常见类群为背刻螨属Epicriopsis、毛绥螨属Lasioseius、吸螨属Bdella、肉食螨属Cheyletus、寄螨属Parasitus、真派盾螨属Euparholaspulus、尾足螨属Uropoda、维螨属Veigaia、厉螨属Hypoaspis、土厉螨Ololaelaps等10类,占总捕获量的30.47;,其余14类为稀有类群,仅占总捕获量的7.96;.在不同生境土壤捕食性螨类个体数和类群数之间差异均为显著(P＜0.05),其中自然榆林最高,菜地最低,个体数顺序为自然榆林＞植物园＞菜地＞防护林＞居民点＞草地.群落类群数及个体数的垂直分布均具有表聚性,不同生境及不同土层间差异均为极显著(P＜0.01),个体数和类群数在不同季节之间差异显著(P＜0.05),其顺序为夏季＞秋季＞冬季＞春季.群落相似性系数在不同生境样地之间基本上属于中等不相似(0.25≤q＜0.50).群落多样性指标在不同生境间差异显著(P＜0.05),其中Shannon - Wiener多样性指数(H)顺序为自然榆林＞植物园＞草地＞菜地＞居民点＞防护林.Margalef丰富度指数(M)顺序为自然榆林＞草地＞植物园＞防护林＞居民点＞菜地.[结论]乌鲁木齐地区土壤捕食性螨类资源相当丰富,因此,为了加强农林害虫的生物控制、提高绿色农产品产量,亟待进一步加强此类资源的保护利用研究.     

Amino Acid Composition of Developing Larval Freshwater Prawn Macrobrachium rosenbergii

Abstract.— Amino acid profiles of freshwater prawn Macrobrachium rosenbergii were determined during early larval stages (I-IX) to provide some baseline biochemical information of the growing larvae. The larvae obtained from several females were stocked into three 250-L tanks at a density of 30 larvae/L. The feeding regime consisted of newly hatched Artemia nauplii and egg custard containing 5% cod liver oil. For each developmental stage, larval samples from each experimental tank were pooled, freeze dried and after acid hydrolysis, the quantification of amino acids was done by a reverse phase high performance liquid chromatography ( N = 2). The highest represented of the total amino acids were for glutamic acid and phenylalanine (with cystine) with ranges from 13.4–16.6 and 9.7–11.5%, respectively, whereas tryptophan (1.4–1.6%). methionine (1.4–2.7%) and histidine (2.9–4.2%) were relatively lower. The levels of the following essential amino acids did not significantly change during larval development: arginine, leucine, phenylalanine (plus cystine), threonine, tryptophan and valine. Despite statistically significant changes that were observed in levels of some amino acids, amino acid composition appeared to be relatively unchanged during the larval growth. The results may suggest that the amino acid requirements of the freshwater prawn is relatively constant during larval life and can be satistied by a suitable protein source that resembles the larval amino acid profile.     

Detection and molecular characterization of infectious spleen and kidney necrosis virus from major ornamental fish breeding states in Peninsular Malaysia

‘Gold standard’ OIE reference PCR assay was utilized to detect the presence of infectious spleen and kidney necrosis virus (ISKNV) in freshwater ornamental fish from Malaysia. From total of 210 ornamental fish samples representing 14 species, ISKNV was detected in 36 samples representing 5 fish species. All positive cases did not show any clinical signs of ISKNV. Three restriction enzymes analyses showed that the fish were infected by identical strains of the same virus species within Megalocytivirus genus. Major capsid protein (MCP) genes of 10 ISKNV strains were sequenced and compared with 9 other reference nucleotide sequences acquired from GenBank. Sequence analysis of MCP gene showed that all strains detected in this study were closely related to the reference ISKNV with nucleotide sequence identity that was ranging from 99.8% to 100%. In addition, phylogenetic analysis of MCP gene revealed that viruses from genus Megalocytivirus can be divided into three genotypes: genotype 1 include reference ISKNV and all other strains that were detected in this study, genotype 2 include viruses closely related to red sea bream iridovirus (RSIV), and genotype 3 include viruses closely related turbot reddish body iridovirus (TRBIV).