A high-throughput glasshouse bioassay to detect crown rot resistance in wheat germplasm

A high-throughput and reliable seedling bioassay to screen wheat germplasm for crown rot resistance was developed. Single wheat seedlings were grown in square seedling punnets in a glasshouse and inoculated with a monoconidial Fusarium pseudograminearum isolate 10 days after emergence. The punnets were laid horizontally on their side and a 10- µ L inoculum droplet placed on the stem base. Seedlings were incubated at near-saturated relative humidity, and crown rot severity was assessed 35 days after inoculation. Studies on the duration of incubation period, inoculum concentration and temperature were carried out to optimize these parameters. Seedling growth at 25/15(±5)°C in a glasshouse and 48-h incubation at near-saturated RH in darkness gave the best results. When crown rot resistance rankings of 16 Australian cultivars from the bioassay were compared with their field performance, Spearman's rank correlation coefficient was highly significant. This indicated that the seedling bioassay mimicked field resistance to crown rot in adult plants. A bootstrap resampling analysis showed little or no improvement in the coefficient of variation with an increasing number of replications, indicating a high level of precision and reproducibility. By detecting small but consistent differences in crown rot severity, the bioassay proved effective in large-scale screening for partial resistance: already over 1400 wheat genotypes have been screened. The high degree of precision makes this an invaluable tool in the understanding of pathogen aggressiveness, host specialization and parasitic fitness.     

Comparing rice germplasm groups for growth, grain yield and weed-suppressive ability under aerobic soil conditions

Germplasm and cultivars need to be selected as parents for breeding weed‐competitive aerobic rice in the tropics. Forty rice (Oryza sativa) cultivars belonging to the aus, indica and tropical japonica germplasm groups, or derived from crosses among them, were evaluated in adjacent weed‐free and weedy trials in aerobic soil conditions during the wet seasons of 2001–2003. The objectives of this study were to assess vegetative growth, grain yield under weed‐free (Y_F) and weedy (Y_W) conditions, and weed‐suppressive ability (WSA) of different germplasm groups. In the first 4 weeks after sowing, indica cultivars had faster growth in height, tillering and crop biomass than other groups. They also had high Y_F, Y_W and strong WSA. Aus cultivars were similar to the indica types in early growth and WSA, but were poor in Y_F. Tropical japonica groups and the group derived from indica/tropical japonica crosses were generally inferior to aus and indica groups in early growth and WSA. Both of their Y_F and Y_W were lower than that of the indica group. Therefore, indica germplasm seemed to be most suitable for breeding high‐yielding and weed‐suppressive aerobic rice for the tropics. The relationship of WSA with various traits within tropical japonica germplasm revealed that fast early growth, rather than plant erectness, is crucial to WSA.     

扁穗牛鞭草种质遗传多样性的ISSR分析

用ISSR标记对来自中国西南地区(四川、重庆、贵州)的28份扁穗牛鞭草材料的遗传多样性进行了检测。从96个ISSR引物中共筛选出13个多态性明显、反应稳定的引物。28份材料的DNA共扩增出129条谱带,平均每个引物扩增出9.9条带,多态性条带比率达84.2%。材料间遗传相似系数为0.466~0.980,表现出丰富的遗传多样性。通过聚类分析和主成分分析,将28份扁穗牛鞭草分为两大类,同一地区的扁穗牛鞭草品种(系)基本聚在同一类,呈现出一定的地域性分布规律。     

Host status and reaction of <Emphasis Type="Italic">Medicago truncatula</Emphasis> accessions to infection by three major pathogens of pea (<Emphasis Type="Italic">Pisum sativum</Emphasis>) and alfalfa (<Emphasis Type="Italic">Medicago sativa</Emphasis>)

Ditylenchus dipsaci, the stem nematode of alfalfa (Medicago sativa), Mycosphaerella pinodes, cause of Ascochyta blight in pea (Pisum sativum) and Aphanomyces euteiches, cause of pea root rot, result in major yield losses in French alfalfa and pea crops. These diseases are difficult to control and the partial resistances currently available are not effective enough. Medicago truncatula, the barrel medic, is the legume model for genetic studies, which should lead to the identification and characterization of new resistance genes for pathogens. We evaluated a collection of 34 accessions of M. truncatula and nine accessions from three other species (two from M. italica, six from M. littoralis and one from M. polymorpha) for resistance to these three major diseases. We developed screening tests, including standard host references, for each pathogen. Most of the accessions tested were resistant to D. dipsaci, with only three accessions classified as susceptible. A very high level of resistance to M. pinodes was observed among the accessions, none of which was susceptible to this pathogen. Conversely, a high level of variation, from resistant to susceptible accessions, was identified in response to infection by A. euteiches.     

10份菠萝种质资源的描述和评价

对收集的10份菠萝种质资源植株的芽、叶片及其果实性状进行描述和评价.结果表明:徐台品种的可溶性固彤物含量最高,其余指标接近于巴厘品种但无刺,是巴厘品种较好的一个替代品种;上海2号品种果型端正,果肉橙黄色,品质中上,Vc含量高,是较好的鲜食和加工皆宜品种;ST品种风味好,口感好,是一个优良的鲜食品种.     

老岭自然保护区的野生果树种质资源

青龙县老岭的野生果树种质资源比较丰富，初步查明有１２种，５０种。简要叙述了主要种的生物学特点及用途，进行了必要的讨论。     

Evaluation,tissue culture propagation,and dissemination of ‘Saba’ and ‘Pelipita’ plantains in Costa Rica

Fruit characteristics of the disease-resistant bluggoe-type (ABB) cooking bananas (Musa × paradisiaca L.) ‘Saba’ and ‘Pelipita’ were compared with those of the susceptible ‘Currare’ (‘Horn’). Yields of ‘Saba’ and ‘Pelipita’ were similar to those of ‘Currare’; however, ‘Saba’ and ‘Pelipita’ yielded fewer hands with a greater number of small fruit when compared with ‘Currare’. Shoot-tip cultures of both clones were readily initiated on a modified Murashige and Skoog (MS) basal medium supplemented with N⁶-benzyladenine (BA) in combination with indole-3-acetic acid (IAA). Propagation cultures were initiated by splitting shoot tips along their longitudinal axis and re-culturing the individual pieces to basal medium supplemented with 5 mg l^?1 BA. Transfer of axillary shoots to hormone-free medium resulted in rapid and extensive root formation. Plantlet survival after transfer to methyl bromide-treated soil exceeded 90%. Establishment in the field was achieved following procedures normally used for vegetative propagation of this crop. Trial plantings of in vitro propagated ‘Saba’ and ‘Pelipita’ were established in various provinces of Costa Rica for grower evaluation and for future comparison of growth and reproductive development with plants of these and other cultivars propagated from corms.     

一种与板栗嫁接亲和性高的茅栗居群及其RAPD分析

在湖北武汉的北部山区发现一种与板栗有较高嫁接亲合性的茅栗居群，3～5年生该茅栗居群做砧木与当地品种大红袍嫁接成活率在80％以上，嫁接后20年仍然能正常结果；应用RAPD技术分析该居群与栽培板栗品种、野生板栗、锥栗的遗传关系，表明该茅栗居群与板栗的亲缘关系紧密，尤其与野生板栗接近。分析认为该茅栗与板栗嫁接亲和性高的原因可能是该茅栗居群“渗入”更多的板栗基因．     

Sesbania seed collections in Southern Africa

The International Centre for Research in Agroforestry (ICRAF) is a member of the Consultative Group on International Agricultural Research (CGIAR) system and has recently established a Multipurpose Tree Germplasm Resource Unit (MPT-GRU) in Nairobi, Kenya. The first major activity of the MPT-GRU was to undertake a regional germplasm collection ofSesbania in 5 countries in southern Africa in a collaborative mode with National Agricultural Research Services (NARS). The collections took place in Botswana, Malawi, Namibia, Zambia and Zimbabwe.Key elements of a generalised collaborative mode (the model) are indicated follwed by a summary of actual events. The initial phase involved joint planning and training sessions between NARS, three sister CGIAR centres and one regional institution, the Southern Africa Development Conference (SADC) Regional Gene Bank (SRGB). This was followed by actual collections during 1993 led by National scientists with different levels of CGIAR participation in each of the five countries. The International Board of Plant Genetic Resources (IBPGR) took the lead in pre-collection training activities, ICRAF for developing the collection programme and the International Livestock Centre for Africa (ILCA) for seed drying, testing and despatch for field trials. NARS gene banks guided the necessary administrative processes. The ICRAF lead scientist for the species and provenance evaluation phase was a crucial member of the planning process thus allowing integration of the collection with the eventual field evaluation. The article focuses on the collection strategy, administrative protocols for actual collections and summary results. Some advantages and difficulties associated with the collection programme and model are discussed. The collections were important in bringing together agriculturalists and foresters in a common germplasm collection exercise.