Variation in phenol, electrical conductivity, and sugar contents in Grewia oppositifolia Roxb.

We estimated variation in the allocation of metabolites (phenol, sugar, and electrical conductance) in seed, fruit and seedling leachates of 25 populations of Grewia. oppositifolia. Higher quantity of phenolics and higher electrical conductance were observed in plants from lower-middle altitudes but this was not correlated significantly with germination, survival, or plant height. On the other hand, sugar content in fruit pulp leachates was greatest in higher elevational populations and these sources also recorded higher germination, survival, and plant height under nursery conditions. Thus we recommend that germplasm (seed) should be collected from moderately higher elevational sources for nursery as well as future breeding strategies of this potential agroforestry tree crop of the central Himalaya.     

Analysis of soil moisture variation by forest cover structure in lower western Himalayas, India

Soil moisture affects various hydrological processes, including evapotranspiration, infiltration, and runoff. Forested areas in the lower western Himalaya in India constitute the headwater catchments for many hill streams and have experienced degradation in forest cover due to grazing, deforestation and other human activities. This change in forest cover is likely to alter the soil moisture regime and, consequently, flow regimes in streams. The effect of change in forest cover on soil moisture regimes of this dry region has not been studied through long term field observations. We monitored soil matric potentials in two small watersheds in the lower western Himalaya of India. The watersheds consisted of homogeneous land covers of moderately dense oak forest and moderately degraded mixed oak forest. Observations were recorded at three sites at three depths in each watershed at fortnightly intervals for a period of three years. The soil moisture contents derived from soil potential measurements were analyzed to understand the spatial, temporal and profile variations under the two structures of forest cover. The analysis revealed large variations in soil moisture storage at different sites and depths and also during different seasons in each watershed. Mean soil moisture storage during monsoon, winter and summer seasons was higher under dense forest than under degraded forest. Highest soil moisture content occurred at shallow soil profiles, decreasing with depth in both watersheds. A high positive correlation was found between tree density and soil moisture content. Mean soil moisture content over the entire study period was higher under dense forest than under degraded forest. This indicated a potential for soil water storage under well managed oak forest. Because soil water storage is vital for sustenance of low flows, attention is needed on the management of oak forests in the Himalayan region.     

Regeneration of tree species in the sub-tropical forest of Alaknanda Valley, Garhwal Himalaya, India

We studied the regeneration of tree species in the sub-tropical forest of Alaknanda Valley in Garhwal Himalaya, India. The overall regeneration status was fairly good in the study area. Seedling density ranged between 520 and 1,240 seedlings per ha while the density of saplings varied between 400 and 800 saplings per ha. Out of eight sites studied, five sites, viz., A1 , A2 , B1 , B2and C2contained the highest number of seedlings (280-480 per ha) and saplings (200-440 per ha) for Pinus roxburghii and remaining three sites viz., C1, D1and D2represented the highest number of seedlings (240-400 per ha) and saplings (200-240 per ha) for Anogeissus latifolius. The DBH class distribution of the tree species revealed that the highest number of individuals was concentrated in the lower diameter classes while smallest numbers were found in the higher diameter classes. Species such as Acacia catechu, Anogeissus latifolius, Dalbergia sissoo, Engelhardtia spicata, Lannea coromandelica, Mallotus philippensis and Pinus roxburghii have the largest number of saplings and seedlings in the lower DBH classes, suggesting that they have good regeneration potential. Other species such as Aegle marmelos, Bauhinia variegata, Bombax ceiba, Cassia fistula, Erythrina variegata, Haldinia cordifolia, Mangifera indica, Ougeinia oojeinensis, Phyllanthus emblica, Syzygium cumini, Terminalia alata and Toona hexandra have either no or very small number of saplings in the lower DBH classes, which indicates that the status of these species implies poor regeneration.     

Effects of variation in seed sources and pre-sowing treatments on seed germination of Tamarindus indica: a multi-purpose tree species in Bangladesh

We investigated the morphology and germination of Tamarindus indica seeds in order to discover the effects of variation in seed sources and pre-sowing treatments on germination. The experiment was carried out in the nursery of the Forestry and Wood Technology Discipline, Khulna University, Bangladesh. Seeds were collected from different but healthy trees from various locations in Bangladesh and subjected to four pre-sowing treatments, i.e., control, immersion in cold water (4°C for 24 h), immersion in hot water (80°C for 10 min) and scarification with sand paper. Seed germination was carried out in poly-bags with a mixture of topsoil and cow dung in the ratio of 3:1. The average length of the fresh seeds was 1.35±0.26 cm, their width 1.07 ±0.20 cm and thickness 0.69±0.11 cm. The results revealed that pre-sowing treatments affected the germination process of seeds, which significantly increased the germination percentage with the cold water (81.67%) and scarification with sand paper (82.33%) treatments, compared with those in the control (58.33%) and hot water treatment (59.00%). In all treatments germination started on average within 5 to 7 days after the start of the treatments and were completed from 13 to 19 days later. The greatest success in germination (82.33%) was found in scarification with sand paper, followed with 81.67% in the cold water treatment. The results of analyses of variance (ANOVA) showed significant differences (p<0.05) in germination closing dates, seed germination periods and germination percentages among the treatments but no significant difference among seed sources. However, the effect of the interaction between seed source variation and pre-treatment differed significantly in seed germination closing dates and germination percentages. We recommend cold water treatment (submersion of seed at a temperature of 4°C for a 24-h period) for seed germination of T. indica in rural Bangladesh.     

基因组学方法研究猪脂肪沉积的遗传机理

猪脂肪性状因能影响肉质和育肥效率而占有重要的地位,与此同时,猪被视为研究人类肥胖症和代谢症候群等诸多疾病的模型动物。当前人类,由于脂肪过度沉积而蔓延全球的肥胖症已演变为一个十分严峻的问题,因此,比较基因组学的运用将会为遗传上研究脂肪和肥胖带来新的视点。脂肪性状是由多个微效基因控制的数量性状,这些遗传因子的相关系数在0.5左右。对猪全基因组扫描显示有500多个数量性状基因座(Quantitative Trait Locus,QTL)跟脂肪形成有关;进一步研究表明:与之相关的多个候选基因多态性已分析出来,包括基因编码的LEP及其受体LEPR、IGF2、FABP3、FABP4、MC4R及FTO。在这些因子中,对猪脂肪形成起到关键作用的是IGF2;与人类肥胖症最为密切的是FTO,然而,该基因对猪脂肪形成作用并不是十分明显。随着功能基因组学的发展,逐步揭示出更多跟脂肪沉积和油脂代谢相关的基因。近年来,以RNA干扰为主的表观基因组学被认为是获得与脂肪沉积相关基因的重要途径。总之,就现有研究成果来看,脂肪性状多态性的遗传背景是高度相关的。     

不同方法控制PRRS病毒的实践经验

上期回顾：为了在 PRRS疫情爆发期间更好地控制猪群临床疾病,上期从传播途径和保护免疫力方面,详细介绍了PRRS循环爆发的观点及猪场控制的方法。     

猪大脑脓肿:猪链球菌2型诱发的脑膜脑炎的典型表现

本文介绍了2.5月龄杂种公猪中与猪链球菌2型感染有关的研究结果.临床上,该动物表现为斜颈、划浆运动、侧卧和惊厥.大脑的大体病变为多发性脓肿,不对称地位于右侧大脑半球,且与脑膜表面粘连.组织病理学分析显示为多病灶型或与病灶内细菌菌落有关的融合型大脑脓肿、化脓性脑膜脑炎和血管炎.生化分析显示,该病灶内细菌为革兰氏阳性球菌,福格斯-普里斯考尔、过氧化氢酶和氯化钠分析呈阴性反应,在海藻糖和水杨苷肉汤培养基中产生酸.利用从大脑脓肿处培养的细菌DNA,通过聚合酶链式反应分析,扩增到了大小为459 bp的猪链球菌2型荚膜基因的部分片段.组织病理学、微生物学和分子学研究结果支持该疾病为由猪链球菌2型诱发的大脑脓肿和脑膜炎的诊断.该病例是猪链球菌性脑膜脑炎一个非典型表现,且据我们所知,是第一次在猪上发现的由猪链球菌2型诱发的大脑脓肿.     

利用外源性酶提高单胃动物产量所面临的机遇和挑战

饲喂单胃动物的日粮主要由植物性原料组成。肌醇六磷酸钙镁、非淀粉多糖和蛋白酶抑制因子等许多抗营养因子可能存在于这些饲料原料中,它们会限制饲喂这些日粮的动物对营养物质的消化吸收。酶制剂被用于单胃动物生产中,用来提高动物生产性能、增加营养物质利用率和降低营养物质排泄量。已使用的酶制剂主要针对植酸和非淀粉多糖。非淀粉多糖消化酶在动物生长性能和营养物质吸收上的作用效果并不太一致,不过人们仍希望并努力设计出针对非淀粉多糖的最适宜的剂量和酶种,进而取得有益效果。本文章尝试去归纳该领域的最新研究,建议扩大开发这个特有的生物产业的机会。     

家禽生物安全的评价及其有效性的启示

生物安全在使家禽生产可持续性与经济可行性中有着无可替代的的作用。但同时,在某个养殖场或系统中,生物安全的做法可能完全取决于最基层员工的选择。这个难题表明,我们需要建立一种方法来进行生物安全程序的质量评价,以确保必要措施的贯彻落实。本文从生物安全的实施方法、达成目标、面对对象、防控范围、评估结构组成及采用工具等方面对家禽生物安全进行概述,并指出了对家禽生物安全进行评价的的重要性。     

利用锌指核酸酶对猪基因组进行定向遗传修饰（续完）

4利用ZFN修饰猪的基因组 早期通过ZFN获得遗传修饰动物的研究开始于将其注射到非洲爪蟾（Xenopus laevis）的卵母细胞中（Bibikova等,2001）。虽然最终没有得到活着的基因敲除蟾蜍,但是这个研究证明了ZFN在活体内具有活性,以及可以通过同源重组介导基因组修饰。