Comparing mating designs to restore seed production of interspecific hybrids between Trifolium repens (white clover) and Trifolium uniflorum

Interspecific hybrids between Trifolium uniflorum and cultivated white clover (Trifolium repens) have highly useful characteristics for temperate pastoral systems derived from both parent species. However, the early hybrids (F₁ and BC₁) also have unacceptably poor seed production for commerce. This study analysed the basis for the poor seed production and investigated breeding strategies for overcoming the problem. The BC₁F₁ generation produced lower‐than‐expected numbers of heads per plant and seeds per floret. Backcrossing of selected hybrids to white clover corrected these deficiencies and created new variation. Seed numbers were also returned to near target levels by recurrent selection within the BC₁ generation. Thus, it was possible to retain a theoretical average of 25% of T. uniflorum genome and still achieve high seed production per plant. The BC₁F₂ and BC₂F₁ generations produced high seed numbers per plant, along with reasonable variation. Both of these second‐generation hybrid forms have high reproductive potential and should be the focus for the selection of the desired combinations of agronomic and seed production traits.     

3种牧草不同搭配方式对胜红蓟的替代控制

研究3种牧草不同搭配方式对胜红蓟的替代控制效果,为入侵杂草胜红蓟的防控提供植物种和替代控制方法.在田间条件下,通过将白三叶、杂交甜高粱、杂交狼尾草3种牧草两两等比例搭配后与胜红蓟按2∶1混种,建立3种不同的替代控制方式,动态监测各群落(种群)植物、土壤微生物指标,评价3种牧草两两等比例搭配对胜红蓟的替代控制效果.结果表明:白三叶、杂交甜高梁等比例搭配对胜红蓟进行替代控制时,2种牧草株高严重受阻,牧草相对盖度占优,Simpson指数和Shannon-wiener指数均变大,胜红蓟重要值变小,土壤真菌增多,细菌、放线菌减少;白三叶、杂交狼尾草等比例搭配对胜红蓟进行替代控制时,2种牧草株高不受阻,牧草相对盖度占优,Simpson指数变大,Shannon-wiener指数变小,胜红蓟重要值变小,土壤真菌增多,细菌、放线菌减少;杂交狼尾草和杂交甜高粱等比例搭配对胜红蓟进行替代控制时,杂交狼尾草株高不受阻,但杂交甜高梁株高严重受阻,牧草相对盖度占优,Simpson指数变小,Shannon-wiener指数变大,胜红蓟重要值变小,土壤细菌增多,真菌、放线菌减少.总体来看,白三叶和杂交狼尾草可以等比例搭配作为胜红蓟替代控制材料,且替代控制效果较好;白三叶和杂交甜高粱、杂交甜高粱和杂交狼尾草不宜等比例搭配作为胜红蓟的替代控制材料.     

红车轴草总黄酮对小鼠免疫功能的影响

［目的］研究红车轴草总黄酮对小鼠免疫功能的影响。［方法］设计迟发变态反应试验、炭粒廓清试验、脏器指数试验,每个试验均用40只小鼠,随机分成4组,设对照组与高、中、低剂量3个试验组。3个试验组分别给予85 mg/（kg·d）（高剂量组）,53 mg/（kg·d）（中剂量组）,22 mg/（kg·d）（低剂量组）红车轴草总黄酮灌胃,对照组以吐温-盐水液灌胃。［结果］3个试验组48 h足跖增厚与对照组均有增加,以中剂量试验组增加显著（P〈0.05）;中剂量组与低剂量组的吞噬指数较对照组有显著增高（P〈0.05）;脏器指数试验结果表明,试验组与对照组均有增加,但没有显著的统计学意义。［结论］试验全面评价了红车轴草总黄酮的各种生理药理功能及其对免疫功能的影响,为其开发应用提供了可靠的参考资料。     

Phosphatase activity in the rhizosphere and its relation to the depletion of soil organic phosphorus

Summary The distribution of phosphatase activity and of phosphate fractions of the soil in the proximity of roots was studied in order to evaluate the significance of phosphatases in P nutrition of various plants (Brassica oleracea, Allium cepa, Triticum aestivum, Trifolium alexandrinum). A considerable increase in both acid and alkaline phosphatase activity in all the four soil-root interfaces was observed. Maximum distances from the root surface at which activity increases were observed ranged from 2.0 mm to 3.1 mm for acid phosphatase and from 1.2 mm to 1.6 mm for alkaline phosphatase. The increase in phosphatase activity depended upon plant age, plant species and soil type. A significant correlation was noticed between the depletion of organic P and phosphatase activity in the rhizosphere soil of wheat (r = 0.99^**) and clover (r = 0.97^**). The maximum organic P depletion was 65% in clover and 86% in wheat, which was observed within a distance from the root of 0.8 mm in clover and 1.5 mm in wheat. Both the phosphatases in combination appear to be responsible for the depletion of organic P.     

盐胁迫对白三叶种子萌发及幼苗生长的影响

研究盐胁迫对白三叶种子抗盐萌发和幼苗生长的影响,结果表明:不同浓度的NaCl胁迫下,白三叶种子的发芽势、发芽率、株高均呈下降趋势,处理和对照之间的差异达到极显著水平;盐胁迫对白三叶叶片的叶绿素含量和根系活力均有一定的影响,叶绿素含量对照与处理之间差异达到极显著水平,根系活力对照与低浓度处理差异不显著,与高浓度处理之间达到极显著水平。     

梅花根际土壤栽培三叶草的丛枝菌根侵染研究

从北京、武汉、南京、重庆、昆明五个梅园和野梅主要分布区的云南嵩明、四川木里、贵州茂兰自然保护区,以及北京林业大学的梅圃中分别于春、夏、秋、冬四季,采集梅花根际土壤300份。以梅花根际土壤和蛭石体积为1∶1混合作为栽培基质,种植三叶草,培养4个月后,应用染色镜检法测定丛枝菌根真菌(AMF)侵染三叶草根系的状况。结果表明:所有梅花根际土壤栽培三叶草都有丛枝菌根侵染;野生梅花根际土壤栽培三叶草的丛枝菌根侵染率高于人工梅园;四季的梅花根际土壤栽培三叶草丛枝菌根侵染在季节间无明显差异。     

白三叶无性系植物种群分株间的资源分配

文中研究了白三叶无性系种群各部分的资源分配。结果表明,水分通过匍匐茎的移动,在母株,幼分枝和老分枝中,水分和氮代谢是整合的。在光、水分和土壤营养充足条件下,新的,幼分枝输入足够的水分和氮,使老分枝和母株促进一个水平。幼分枝的输出并没有降低相互联接的老分枝和母株的生长,根的能值与年龄显著相关,植物体的各部分的能值各异。     

Effects of replacing timothy silage by alsike clover silage on performance,carcass traits and meat quality of finishing Aberdeen Angus and Nordic Red bulls

The objective of the study was to determine the effects of silage plant species and cattle breed on performance and meat quality of finishing bulls. A feeding experiment was conducted using thirty Aberdeen Angus (AA) and thirty Nordic Red (NR) bulls. Both breeds were randomly allotted to three experimental diets. The composition (g kg^?1 dry matter) of the diets was as follows: (i) timothy silage (TS) (650) and barley (350); (ii) TS (325), alsike clover silage (AS) (325) and barley (350); and (iii) AS (650) and barley (350). The bulls were fed a total mixed ration ad libitum. Replacing TS by AS did not affect dry‐matter intake, growth, carcass conformation or meat quality traits of the bulls, but carcass fat score tended to decrease when replacing TS by AS (P = 0·07). The AA bulls grew faster and had better feed conversion and superior carcass conformation compared with the NR bulls (P < 0·001). The loin of the AA bulls had lower shear force value and was given higher scores in sensory analyses compared with the NR bulls (P < 0·01). The experiment demonstrated that replacing TS by AS in the diet of finishing bulls had minor effects on performance or meat quality.     

Estimates of heritability for,and relationships between,root and shoot characters of white clover. I. Replicated clonal material

Summary A total of 749 genotypes from a number of white clover (trifolium repens L.) cultivars and populations, many collected from dryland areas, were cloned and grown in field titles. Several morphological characters, including leaf size, number and diameter of large nodal roots (taproots), and proportion of root weight that was classified as taproot were measured. There was large variation between lines and genotypes for all characters measured, and differences between genotypes within lines are also reported. Broad sense heritability estimates were higher (>0.5) for leaflet width, petiole length and stolon diameter, than for all root character heritability estimates which were between 0.2 and 0.4.     

白三叶种子催芽技术与育苗基质的研究

以白三叶(Trifoliu mrepens)种子为试验材料,研究水浸时间、育苗基质类型、不同浓度赤霉素与硝酸钾浸种处理对白三叶种子发芽的影响。结果表明,水浸24h可极显著提高种子发芽指数、萌发活力指数、发芽势和发芽率,与未浸种的相比发芽率可提高10%-13%;基质类型对种子的发芽指数和萌发活力指数影响均达到显著水平,种子较适合的催芽浓度与育苗基质组合为50mg·L-2赤霉素、0.2%硝酸钾、园土∶沙∶泥炭土=2∶1∶1,平均发芽率达31.67%,平均萌发活力指数达42.212。