种间竞争梯度对白车轴草与其病原菌白车轴草单孢锈菌相互作用的影响（英文） 刘登义 Lars Ericson

 白车轴草(Trifolium repens)在与其病原菌白车轴草单孢锈菌(Uromyces trifolii-repentis)的长期相互作用中分化形成了抗病型(Resistance)无性系和易感型(Susceptibility)无性系。该研究工作旨在了解：1)在种间竞争不断增强的环境梯度中,抗病型无性系和易感型无性系的生长表现有何区别?2)在同样的实验条件下,分别对抗病型无性系和易感型无性系进行接种感染后,两者的生长表现又有何区别?在一严重感病的白车轴草自然种群中,分别标定17个抗病型无性系和14个易感     

Sex ratio of some long-lived dioecious plants in a sand dune area

In dioecious plants the fraction of males among flowering plants in the field (the secondary sex ratio) is the result of the fraction of males in the seeds (the primary sex ratio) and the subsequent survival and age at first reproduction of the two genders. It has been assumed that survival and age at first reproduction are the main determinants of biased secondary sex ratio but, especially for long-lived perennials, few data are available. We address this issue for natural populations of four long-lived perennials in a dune area. In Asparagus officinale and Bryonia dioica, the secondary sex ratio was unbiased. In Salix repens the secondary sex ratio was female-biased (0.337). Hippophae rhamnoides populations were male-biased; the average sex ratio of flowering plants was 0.658, while the fraction of males varied between 0.39 near the sea to 0.84 at the inland side of the dunes. The primary sex ratio was estimated by germinating seeds and growing plants under favourable conditions with minimal mortality. In S. repens the primary sex ratio in seeds was variable among mother plants and was, on average, female-biased (0.289). This is close to the secondary sex ratio, suggesting that the female bias already originates in the seed stage. In Hippophae rhamnoides the primary sex ratio was slightly male-biased (0.564). We argue that in this species, apart from the primary sex ratio, higher mortality and a later age at first reproduction for females contribute to the strong male bias among flowering plants in the field.     

Variation amongst survivor populations of white clover collected from sites across Europe: growth attributes and physiological responses to low temperature

Experiments were carried out at IGER, Aberystwyth, UK to investigate traits of direct relevance to the processes of overwintering and spring growth in white clover (Trifolium repens L.). The plant material used was derived from baseline populations of the cultivar AberHerald and survivor populations generated after 2-3 years' growth in Germany (Kiel), Sweden (Uppsala) and Switzerland (Zürich). The aims of the experiments were to measure the level of genetic shift that had occurred in certain traits due to selection in the survivor populations by comparing these with the baseline population. The adaptive significance of traits was assessed by determining the extent to which stabilizing selection had operated to reduce levels of intra-population variation. Significant differences were found in the responses of leaf production to two temperature treatments in the survivor populations from Germany and Sweden compared with the Swiss and baseline material. Plants of the former two populations produced much more leaf than the others at the higher temperature, but leaf production rates at the lower temperature did not differ. As this experiment used cloned genotypes in the two treatments, the result suggests that a higher degree of phenotypic plasticity for this trait had been selected for in the German and Swedish populations. These populations also showed greater rates of regrowth of leaves from terminal buds exposed to sub-zero temperatures, but there were no differences between populations in levels of freezing tolerance, or in stolon carbohydrate content. Genetic shift occurred in the degree of unsaturation of stolon lipids, with all three survivor populations possessing higher proportions of unsaturated fatty acids than the baseline. Stabilizing selection also operated on this trait in the survivor populations, suggesting that it is of adaptive significance in cool climates.     

Interaction between Sitona lepidus and red clover lines selected for formononetin content

Adult clover root weevil Sitona lepidus show a feeding preference for white clover Trifolium repens over red clover Trifolium pratense. The effects on S. lepidus of three red clover T. pratense lines, selected for high, medium, or low levels of the isoflavone formononetin in foliage, were compared in three experiments using white clover as a control. In a no‐choice slant board experiment, weevil larval weights were greater for larvae feeding on white clover roots than those feeding on roots of the red clovers. The effect of larval root herbivory on plant growth was similar for all four clovers. Following root herbivory, a large increase in root and shoot formononetin levels was observed in the high‐formononetin selection of red clover but little change in the low‐formononetin red clover. In a no‐choice experiment with sexually mature female adult weevils feeding on foliage of the four clovers, all the red clovers had increased weevil mortality. Female weevils eating the high‐formononetin red clover laid fewer eggs than weevils eating white clover. The red clover diet caused a large accumulation of abdominal fat and/or oil in the weevils, whereas weevils feeding on white clover did not accumulate fat/oil. When sexually immature adult weevils were given a choice of foliage from all four clovers, white clover was eaten preferentially, and the low‐formononetin red clover was preferred to the high‐formononetin red clover. The results suggest that formononetin and associated metabolites in red clover may act as chemical defences against adult S. lepidus and that distribution in forage legumes can be manipulated by plant breeding to improve root health.     

Rhizobium trifolii mutants deficient in exopolysaccharide production

Spontaneous mutants of Rhizobium trifolii 24AR5 which did not produce exopoly-saccharide were isolated. The non-mucoid mutants formed small white and ineffective nodules on both red and white clover. These nodules contained infection threads, but only a small number of bacteria were released into nodule cells, and bacteroids were rarely observed. The non-mucoid phenotype was not complemented by the symbiotic plasmid (pJB5JI) of Rhizobium leguminosarum.     

一个超矮秆核质杂种小麦的初步研究

在用普通小麦对长穗偃麦草(Etytrigia elongata=Agropyron elongatum,2n=70)的核代换回交过程中,在BC_9F_1发现了一个超矮秆核质杂种小麦,株高35厘米左右,定名为小偃矮。细胞学观察和与普通小麦正反杂交的遗传分析,证明:(1) 小偃矮是一个异源胞质单体附加系(21″W+1′Ag);(2) 长穗偃麦草细胞质和附加的外来染色体没有携带矮秆基因;(3) 矮秆遗传主要受细胞核内一对显性矮化基因控制。     

Root hair deformation in the white clover/Rhizobium trifolii symbiosis

Rhizobium trifolii most frequently infects its host white clover (Trifolium repens L.) by means of infection threads formed in markedly curled root hairs. Rhizobium infections are classified as either lateral or apical based on whether they originate in the branches or at the apex of the root hairs. A quantitative estimate of lateral and apical infection in the region of the host root (Trifolium repens L. cv. Regal Ladino) that possessed mature and immature root hairs at the time of inoculation with Rhizobium trifolii TAI (CSIRO, Canberra City, Australia) indicated that lateral infection occurred more frequently in the mature root hair region of the root. Apical infections were more common in the immature root hair region. Cell free filtrates collected from R. trifolii cultured in association with the host roots induced branching in white clover root hairs. A partially purified preparation of the branching factor was obtained from freeze-dried filtrates by ethanol extraction and ion exchange chromatography. Preliminary studies on the characteristics of these substances suggest that some are dialyzable and heat stable white others are non-dialyzable and heat labile. The dialyzable, heat-stable compounds contain neutral sugars and range between 1200 to 10000 daltons in size. In roots that were exposed to low concentrations (6–25 μg-ml^?1) of these partially purified deformation factors before inoculation, the developmentally mature root hairs were deformed at the time of inoculation. Nodules appeared in the mature and immature root hair region of these plants at the same time. In plants exposed to water, nodules were observed in the immature root hair region and mature root hair regions 3 and 5 days after inoculation, respectively. Based on these results, we conclude that the nodule development was hastened in the plants exposed to the root hair-deforming substances because the mature root hairs of these plants were made infectible at the time of inoculation by this exposure.     

Growth response of native shrubs to acid mine spoil and to proposed soil amendments

Successful reclamation of acid mine sites may be enhanced by revegetating with species that are tolerant to acid mine spoil conditions. This study was conducted to assess the response of four native shrub species, Amelanchier alnifolia Nutt., Symphoricarpos albus (L.) Blake, Berberis repens Lindl., and Ceanothus sanguineus Pursh, to 1) pyritic acid mine spoil amended with various levels of lime and composted sewage sludge with added ammonium nitrate (CSS+N) and 2) acidified granitic spoil, with and without CSS+N. Species responded to soil acidity and nutrient supply similarly in both spoil materials. Berberis and Amelanchier exhibited acid soil tolerance, Symphoricarpos grew poorly in acidic soils but had low mortality, and Ceanothus responded to low pH with very poor growth, high mortality, or both. Amelanchier was conservative in growth and did not respond to either soil pH or nutrient supply with significant differences in biomass accumulation. Symphoricarpos varied in response to CSS+N but was most productive at neutral or higher pH. Berberis responded to nutrient availability with substantial increases in biomass production, including significant growth in strongly acidic spoil. Ceanothus responded to nutrient availability with large increases in biomass and was most productive with added CSS+N at neutral or higher pH. Nitrogen fixing nodules developed on the roots of Ceanothus plants grown in granitic spoil without CSS+N. The results indicated that these species differ significantly in acid soil tolerance and in their potential for growth, stress tolerance, and resource acquisition.