Influence of pasture botanical composition and fertilization treatments on tree growth

Silvopastoral systems, which combine tree and pasture production, are more complex ecosystems than exclusively agronomic systems. Good silvopasture management should seek to increase positive interactions (or synergies) and reduce negative interactions among system components (soil, trees, grass and cattle) to increase global system productivity. Tree growth and pasture production within such systems can be optimized through appropriate species selection and fertilization. The aim of the present study, carried out over the course of 3 years, was to compare how traditional fertilisation, sewage sludge dose, and potassium affect pasture-tree competition, botanic composition and tree growth in a silvopastoral system located on agricultural land during the early years of system development. The addition of potassium is recommended for improving tree growth in silvopastoral systems with slightly acidic soil, especially if the pasture has high legume content. White clover is a good choice of species for silvopastoral systems because it promotes tree growth. Our study revealed that pasture production improved when sewage sludge was used as a fertiliser, but annual production was still more strongly dependent on weather conditions.     

Assessing the impact of agricultural forage crops on soil biodiversity and abundance

Maintaining soil biodiversity and function is key to maintaining soil health, nutrient cycling and decomposition. Different forage species have variable concentrations of essential nutrients and rooting patterns, potentially affecting soil biology and soil–plant–animal interactions. Our study compared the effect of growing different forage crops on soil faunal diversity and abundance. Plots of chicory (Cichorium intybus), red clover (Trifolium pratense), white clover (Trifolium repens) or perennial ryegrass (Lolium perenne) were established in 2009 and maintained over a four year period. Soil faunal samples were taken, including soil mesofauna, nematodes and earthworms, at the end of this period in autumn 2012 and spring 2013. Significant differences were found between the forages for a number of biological groups, as well as some seasonal differences; overall earthworm abundance and biomass was higher within the white clover treatment, specifically anecic earthworms. Nematode functional groups were found to differ, with greater numbers of fungal feeders in the clovers and chicory treatments, whilst the herbivores had the greatest abundances in the two ryegrass treatments. Overall the microarthropod order abundances did not differ, however two collembolan superfamilies did show differences between treatments with the detritivorous Poduromorpha having a higher abundance in the clovers and chicory treatment and the herbivorous Symphypleona had a higher abundance in the ryegrass treatment. Relatively little is known about the links between soil biology and the effects of plant type because of the complex nature of soil, however here we have begun to reveal some of these linkages. Overall, the findings indicate a relationship between ryegrass and herbivorous invertebrates, whilst the other forages have a stronger relationship with decomposer invertebrates; changing the dominance within the soil food web dependent on forage type.     

香根草·苜蓿和三叶草对土壤盐分降解试验研究

[目的]为比较香根草、苜蓿和三叶草对土壤盐分的降解能力。[方法]用不同等级的NaCl溶液或K2SO4溶液定期、定量浇灌栽培在同质地土壤上的香根草、苜蓿和三叶草,分析香根草的成活率、分蘖率和香根草、苜蓿和三叶草的生物量积累率及植株体内的盐分含量及土壤盐分的减少量,并进一步比较香根草、苜蓿和三叶草吸收土壤中盐分的质量、能力和降解盐分的量、能力。[结果]香根草、苜蓿和三叶草都对土壤中盐分都有一定的降解能力,且苜蓿能力最强,香根草能力次之,三叶草能力最弱。[结论]香根草、苜蓿和三叶草对土壤中盐分的降解能力与土壤中盐度有关,同时它们对土壤中盐分的吸收是选择性的。     

红三叶组织培养及再生植株

本文采用ＭＳ，Ｂ５和ＰＣ一Ｌ２作为基本培养基，在不同激素组合条件下对红三叶（Ｔｒｉｆｏｌｉｕｍｐｒａｔｅｎｓｅ）子叶及下胚轴进行组织培养。在ＭＳ，Ｂ５和ＰＣ一Ｌ２附加２ｍｇ／Ｌ２，４－Ｄ和０．５ｍｇ／ＬＢＡ的培养基上，子叶及下胚轴愈伤组织诱导率均在８９％以上。愈伤组织继代在Ｂ５无机盐十三倍ＭＳ有机成分＋３％蔗糖＋０．５ｍｇ／Ｌ２，４－Ｄ＋０．５ｍｇ／Ｌ６ＢＡ０．２ｍｇ／ＬＮＡＡ，＋１０ｍｇ／ＬＶｃ的培养基上生长良好。愈伤组织在Ｂ５附加０．１ｍｇ／Ｌ６ＢＡ＋０．２ｍｇ／ＬＩＢＡ的培养基上再生植株。下胚轴在ＭＳ附加２ｍｇ／Ｌ６ＢＡ＋１ｍｇ／ＬＮＡＡ的培养基上直接分化形成丛生苗，转入无激素ＮＳ培养基上再生根。实验表明ＶＥ，Ｖｃ，ＰＶＰ和活性碳对愈伤组织褐化有抑制作用，１０ｍｇ／ＬＶｃ抗褐化作用最好。     

Intraspecific variation in <Emphasis Type="Italic">Trifolium pratense</Emphasis>: impact on feeding and host location by <Emphasis Type="Italic">Sitona lepidus</Emphasis> (Coleoptera,Curculionidae)

Red clover (Trifolium pratense L.) is becoming increasingly important in grassland systems because of its high productivity, protein content and nitrogen-fixing ability, but its use has been constrained by losses due to pests and diseases, and this contributed to the decline of red clover usage allowing white clover (T. repens L.) to become the dominant legume of UK grasslands. One of the major pests of red clover is the clover root weevil (Sitona lepidus Gyllenhal, Coleoptera, Curculionidae) which attacks both the shoots and roots, particularly the N-fixing root nodules, of clover plants. This current work investigates the feeding preferences of S. lepidus with respect to 11 varieties (Pawera, Kuhn, Astra, Norseman, Norseman low, Norseman high, Marcom, Merviot, Milvus, Britta, Sabtoron) and 5 lines (AA30, AA31, AA4493, AA4494 and AA4495) of red clover in order to identify relationships between the variation in attractiveness of different red clover varieties for both adult and larval stages of the weevil. Of those tested Norseman high showed potential resistance, being less favoured by both adults and larvae of the weevil. This may be attributed to the potentially high phyto-oestrogen levels in this variety.     

The first detection of ‘<Emphasis Type="Italic">Candidatus</Emphasis> Phytoplasma trifolii’ in <Emphasis Type="Italic">Rhododendron</Emphasis> hybridum

Four Rhododendron hybridum plants (from cvs Moravanka and Don Juan), all exhibited symptoms of shortened axillary shoots, reduced leaves with vein clearing and yellowing, undeveloped flowers, and general stunting in a rhododendron nursery garden in southern Bohemia in 2007. Electron microscopy examination of ultra-thin sections revealed the presence of numerous polymorphic phytoplasma-like bodies in the phloem tissue of leaf midribs and petioles. The phytoplasma etiology of this disease was further confirmed by polymerase chain reaction (PCR) using universal phytoplasma primers. Restriction fragment length polymorphism (RFLP) analysis of amplification products obtained with a R16F2/R16R2 primer pair from all symptomatic plants indicated the presence of phytoplasma from the 16SrVI-A subgroup. A detailed comparison of the amplified sequences and phylogenetic analysis confirmed that the phytoplasma belonged to the subgroup 16SrVI-A (clover proliferation phytoplasma group). This is the first report of the natural occurrence of ‘Candidatus Phytoplasma trifolii’ in plants of Rhododendron hybridum.     

The <Emphasis Type="Italic">cyv-2</Emphasis> resistance to <Emphasis Type="Italic">Clover yellow vein virus</Emphasis> in pea is controlled by the eukaryotic initiation factor 4E

The same mutant allele of eukaryotic initiation factor 4E (eIF4E) that confers resistance to Pea seed-borne mosaic virus (sbm-1) and the white lupine strain of Bean yellow mosaic virus (wlv) also confers resistance to Clover yellow vein virus (ClYVV) in pea. The eIF4E genes from several pea lines were isolated and sequenced. Analysis of the eIF4E amino acid sequences from several resistant lines revealed that some lines, including PI 378159, have the same sequence as reported for sbm-1 and wlv. When eIF4E from a susceptible pea line was expressed from a ClYVV vector after mechanical inoculation of resistant PI 378159, the virus caused systemic infection, similar to its effects in susceptible line PI 250438. The resistance to ClYVV in line PI 378159 was characterized through a cross with PI 193835, which reportedly carries cyv-2. Mechanical inoculation of the F1 progeny with ClYVV resulted in no infection, indicating that the resistance gene in PI 378159 is identical to cyv-2 in PI 193835. Furthermore, particle bombardment of pea line PI 193835 with infectious cDNA of ClYVV (pClYVV/C3-S65T) resulted in the same resistance mode as that described for PI 378159. These results demonstrate that the resistance to ClYVV conferred by cyv-2 is mediated by eIF4E and that cyv-2 is identical to sbm-1 and wlv.     

马铃薯Y病毒属三种病毒通用型单克隆抗体的鉴定

构建了马铃薯Y病毒属的大豆花叶病毒(Soybean mosaic virus,SMV)、马铃薯Y病毒(Potato virus Y,PVY)、三叶草黄脉病毒(Clover yellow vein virus,CLYVV)的原核表达载体pET28-SMV CP、pET28-PVY CP和pET28-CLYVV CP,经IPTG诱导、表达和纯化,获得SMV、PVY和CLYVV的CP蛋白。采用ELISA方法,用9株实验室制备的单克隆抗体对含SMV、PVY、CLYVV的病毒汁液和纯化的重组CP蛋白进行检测分析。结果表明,9株单克隆抗体均识别SMV病毒,2D3、4F9、4G12和6E7单克隆抗体能够识别PVY病毒,4F9和4G12能够识别CLYVV病毒,但PVY、CLYVV病毒与抗体的亲和力低于SMV病毒;对于重组表达的衣壳蛋白:SMV、CLYVV与抗体2D3、4F9、4G12和6E7反应强烈,PVY与4F9和4G12抗体反应稍强。综上,本研究鉴定出能识别SMV、PVY、CLYVV的通用单克隆抗体4F9和4G12。     

X射线和荧光照射对三叶草叶片超微弱发光的影响比较研究

[目的]比较X射线和荧光对三叶草叶片超微弱发光的影响。[方法]以长势基本相同的三叶草叶片为材料,测定自身发光,然后分别用X射线和荧光照射,测定延迟发光曲线,比较延迟发光曲线和总光子数与自身发光的差别。[结果]X射线照射后,三叶草叶片的总光子数减少,且拟合曲线近似直线。X射线照射后叶片延迟发光明显受到抑制,抑制作用与照射时间呈正相关。荧光照射10～30s后,叶片延迟发光的光子数明显增多,延迟发光曲线快速升高,然后呈指数衰减,在很短时间内恢复稳定。[结论]三叶草叶片经X射线照射后延迟发光受到明显抑制,经荧光照射后延迟发光有很大幅度增强,延迟发光曲线随时间呈指数衰减。