紫外线诱导小麦条锈菌毒性突变及突变体的RAPD分析

以夏孢子相对致死率90%左右作为紫外线处理最适时间,发现8min为小麦条锈菌条中29号单孢菌系(CY29-3)最适处理时间,其夏孢子相对致死率达88.97%。CY29-3的夏孢子经紫外线处理、扩繁、筛选品种筛选及4代的稳定选择后,获得了两个毒性变异的突变菌株。毒性突变产生的Jubi菌株对尤皮Ⅱ号的毒性增强,反应型由野生菌系的0型变为4型;非毒性突变产生的Funo菌株在阿夫上的反应型由野生菌系的4型变为2型。研究结果表明两突变菌株在鉴别寄主上的反应型和毒性范围也明显不同于野生菌系,说明紫外线诱导的小麦条锈菌变异是不定向和复杂的。对野生菌系和两个突变菌株进行RAPD分析后发现,两突变菌株与野生菌系之间的DNA多态性存在显著差异,多态率分别为10.58%和11.57%,说明紫外线可使小麦条锈菌基因组DNA发生较大的变化且突变位点比较复杂。     

Genetic differences in fruit-set patterns are determined by differences in fruit sink strength and a source : sink threshold for fruit set

Background and Aims

Fruit set in indeterminate plant species largely depends on the balance between source and sink strength. Plants of these species show fluctuations in fruit set during the growing season. It was tested whether differences in fruit sink strength among the cultivars explained the differences in fruit-set patterns.

Methods

Capsicum was chosen as a model plant. Six cultivars with differences in fruit set, fruit size and plant growth were evaluated in a greenhouse experiment. Fruit-set patterns, generative and vegetative sink strength, source strength and the source : sink ratio at fruit set were determined. Sink strength was quantified as potential growth rate. Fruit set was related to total fruit sink strength and the source : sink ratio. The effect of differences observed in above-mentioned parameters on fruit-set patterns was examined using a simple simulation model.

Key Results

Sink strengths of individual fruits differed greatly among cultivars. Week-to-week fruit set in large-fruited cultivars fluctuated due to large fluctuations in total fruit sink strength, but in small-fruited cultivars, total fruit sink strength and fruit set were relatively constant. Large variations in week-to-week fruit set were correlated with a low fruit-set percentage. The source : sink threshold for fruit set was higher in large-fruited cultivars. Simulations showed that within the range of parameter values found in the experiment, fruit sink strength and source : sink threshold for fruit set had the largest impact on fruit set: an increase in these parameters decreased the average percentage fruit set and increased variation in weekly fruit set. Both were needed to explain the fruit-set patterns observed. The differences observed in the other parameters (e.g. source strength) had a lower effect on fruit set.

Conclusions

Both individual fruit sink strength and the source : sink threshold for fruit set were needed to explain the differences observed between fruit-set patterns of the six cultivars.     

Stability of Sweet Potato Cultivars to Alternaria Leaf and Stem Blight Disease

Alternaria leaf petiole and stem blight is an economically important disease of sweet potato ( Ipomoea batatus L.) in tropical and sub-tropical environments. Published research on cultivar resistance to the sweet potato disease is limited. To evaluate cultivar reaction and stability to the disease, multi-location and replicated experiments were established in 12 environments in Uganda. Disease severity (area under disease progress curves – AUDPC), and cultivar root yield were also assessed. Significant differences (P < 0.001) in AUDPC were detected among cultivars. Mean AUDPC ranged from 46.3 (Araka Red) to 78.4 (New Kawogo) across locations and seasons and the genotypes Araka Red and Tanzania had the lowest disease values. The location and season effects accounted for 67.1% and 7.5% of the total variance of AUDPC recorded among cultivars. The ranking of cultivars based on predicted AUDPC from Additive Main Effect and Multiplicative Interactive model (AMMI) showed that the NASPOT 1, the susceptible check, and New Kawogo were most susceptible to the disease in 11 of the 12 environments. Low and stable disease was consistently recorded and predicted on NASPOT 3 and the landrace cultivars Tanzania, Dimbuca, and Araka Red across environments. These results suggest that landrace cultivars had relative stability to the disease and wide adaptation across environments. These results suggest that AMMI statistical model and other multivariate techniques can be utilized for prediction of Alternaria disease stability in these locations.     

Floral sex allocation and reproductive success within inflorescences of Hosta ventricosa,a pseudogamous apomict

Aims Within inflorescences of sexually reproducing hermaphrodites, the production of ovules, fruits and seeds commonly declines from basal (early-opening) to distal (late-opening) flowers, while pollen production remains constant or only changes slightly, with the result that distal (late-opening) flowers become functionally male. However, few empirical studies have specifically examined whether or not changes in allocation to pollen production actually lead to changes in the number of seeds sired, a more direct measure of male fitness. In pseudogamous apomicts, fitness depends on the number of seeds produced; thus, a contrasting pattern of variation in the pollen-to-ovule (P/O) ratio within inflorescences might be expected.Methods We investigated floral sex allocation and reproductive success within racemes of Hosta ventricosa, a pseudogamous apomictic hermaphrodite possessing flowers that open acropetally. We quantified variations in pollen number, ovule number, the P/O ratio and fruit and seed production, from 2007 to 2011, among flowers within racemes of four populations of H. ventricosa in southwest China. Ecological causes for fruit and seed production were evaluated by observing patterns of pollen deposition, flower removal and supplemental pollination.Important findings Pollen number, ovule number and the P/O ratio declined from basal-to-distal positions in all sampled populations (years). Fruit and seed production decreased distally in most populations (years). Low fruit and seed set of distal flowers was not due to pollen limitation because pollen deposition never declined distally and the low fruit and seed set of distal flowers remained even after supplementary pollination was provided. The flower-removal experiment indicated that inter-fruit competition for resources among flowers was common. The low P/O ratio of distal flowers in H. ventricosa might be favored because they were unable to obtain fitness by donating pollen and siring seeds on other plants. Our study may help to understand the adaptive significance of sex allocation among flowers within inflorescences of sexually reproducing hermaphrodites.     

测墒补灌对不同穗型小麦品种耗水特性和干物质积累与分配的影响

在田间试验条件下, 以中穗型小麦(Triticum aestivum)品种‘山农15’和大穗型品种‘山农8355’为供试材料, 设置3个0-140 cm土层土壤相对含水量处理: W0 (拔节期65%, 开花期60%)、W1 (拔节期70%, 开花期70%)、W2 (拔节后8天70%, 开花后8天70%), 采用测墒补灌的方法补充土壤水分达到目标相对含水量, 对两个不同穗型小麦品种的耗水特性和干物质积累与分配进行了研究。结果表明: (1)两品种籽粒产量均以W0处理最低, ‘山农15’ W1和W2处理无显著差异, ‘山农8355’ W1处理显著高于W2处理; 两品种W1处理的水分利用效率和灌溉水利用效率均显著高于W2处理。‘山农15’ W1处理的籽粒产量和灌溉水利用效率分别显著低于和高于‘山农8355’的W1处理, 水分利用效率无显著差异; 两品种W2处理的籽粒产量、水分利用效率和灌溉水利用效率均无显著差异。(2)两品种总耗水量以W0处理最低, ‘山农15’ W1处理显著低于W2处理, ‘山农8355’两处理无显著差异; 两品种W1处理的土壤供水量及其占总耗水量的比例显著高于W2处理。‘山农15’ W1处理的总耗水量和灌水量占总耗水量的比例显著低于‘山农8355’, 土壤供水量占总耗水量的比例显著高于‘山农8355’; 两品种W2处理总耗水量, 土壤供水量及其占总耗水量的比例无显著差异。(3)两品种W1处理成熟期干物质积累量显著高于其他处理, W1处理提高了‘山农8355’开花后干物质积累量及其对籽粒的贡献率, 对‘山农15’无显著影响。‘山农15’ W1和W2处理成熟期干物质积累量显著低于‘山农8355’, 开花前贮藏同化物向籽粒的转运量和转运率、对籽粒的贡献率均显著高于‘山农8355’, 开花后干物质积累量及其对籽粒的贡献率低于‘山农8355’。综合考虑干物质积累与分配、籽粒产量、水分利用效率和灌溉水利用效率, W1处理是两品种节水高产的最佳土壤相对含水量处理。     

53个猕猴桃品种(品系)亲缘关系的SCoT分析

现有主流猕猴桃品种的遗传背景相对单一,亲本来源地理分布狭窄,亲缘关系不清晰.为充分利用杂种优势,该研究以广西植物研究所猕猴桃种质资源圃收集的53个猕猴桃品种(品系)叶片为材料,使用SCoT分子标记进行遗传多样性分析.结果表明:(1)10条引物在53份猕猴桃供试材料中共扩增出110条条带,各引物扩增的条带在8～15条之间...     

The relative importance of architecture and resource competition in allocation to pollen and ovule number within inflorescences of Hosta ventricosa varies with the resource pools

Background and Aims

Allocation of resources to floral traits often declines distally within inflorescences in flowering plants. Architecture and resource competition have been proposed as underlying mechanisms. The aim of the present study is to assess the relative importance of resource competition and architectural effects in pollen and ovule production on racemes of Hosta ventricosa, an apomictic perennial herb.

Methods

Combinations of two defoliation treatments (intact and defoliated) and two fruit-set treatments (no-fruit and fruit) were created, and the roles of architecture and resource competition at each resource level were assessed.

Key Results

Pollen and ovule number per flower increased after defoliation, but pollen to ovule ratio per flower did not change. Pollen, ovules and the pollen to ovule ratio per flower declined distally on racemes at each resource level. In the intact treatment, fruit development of early flowers did not affect either pollen or ovule number of late flowers. In the defoliated treatment, fruit development of early flowers reduced both pollen and ovule numbers of late flowers due to over-compensation caused by defoliation. Late flowers on defoliated fruit racemes produced less pollen than intact fruit racemes but the same number of ovules; therefore, the reduction in pollen number was not caused by over-compensation. In addition, the fruit-set rate of early flowers during flowering was higher in intact racemes than in defoliated racemes.

Conclusions

In flowering plants, the relative importance of architecture and resource competition in allocation to pollen and ovules may vary with the resource pools or the overall resource availability of maternal plants.     

Centennial olive trees as a reservoir of genetic diversity

Background and Aims

Genetic characterization and phylogenetic analysis of the oldest trees could be a powerful tool both for germplasm collection and for understanding the earliest origins of clonally propagated fruit crops. The olive tree (Olea europaea L.) is a suitable model to study the origin of cultivars due to its long lifespan, resulting in the existence of both centennial and millennial trees across the Mediterranean Basin.

Methods

The genetic identity and diversity as well as the phylogenetic relationships among the oldest wild and cultivated olives of southern Spain were evaluated by analysing simple sequence repeat markers. Samples from both the canopy and the roots of each tree were analysed to distinguish which trees were self-rooted and which were grafted. The ancient olives were also put into chronological order to infer the antiquity of traditional olive cultivars.

Key Results

Only 9·6 % out of 104 a priori cultivated ancient genotypes matched current olive cultivars. The percentage of unidentified genotypes was higher among the oldest olives, which could be because they belong to ancient unknown cultivars or because of possible intra-cultivar variability. Comparing the observed patterns of genetic variation made it possible to distinguish which trees were grafted onto putative wild olives.

Conclusions

This study of ancient olives has been fruitful both for germplasm collection and for enlarging our knowledge about olive domestication. The findings suggest that grafting pre-existing wild olives with olive cultivars was linked to the beginnings of olive growing. Additionally, the low number of genotypes identified in current cultivars points out that the ancient olives from southern Spain constitute a priceless reservoir of genetic diversity.     

Lectin in five soybean cultivars previously considered to be lectin-negative

Hemagglutinating proteins were isolated by affinity chromatography from seeds of each of five cultivars of soybeans (Clycine max (L.) Merr.) previously reported to lack detectable lectin (S.P. Pull et al., 1978; Science 200, 1277). Quantities were between 1,000 and 10,000 times less than that found in the seeds of the reference cultivar, Chippewa. The sensitivity of the hemagglutinating assay was 0.05 g ml^-1. Hemagglutinating activity was demonstrated in affinity-purified fractions from bulk seeds and seeds from individual plants in two cultivars, 30–70% ammonium-sulfate-precipitable fractions of seeds from individual plants of all five cultivars, and in whole crude extracts of individual seeds from each cultivar. In all instances, hemagglutinating activity was inhibited by galactose, anti-soybean agglutinin (SBA), and lectin-binding polysaccharide produced by Rhizobium japonicum. Affinity-purified lectin from seeds of a single Columbia plant was labeled with fluorescein isothiocyanate (FITC) and observed by fluorescence microscopy to bind to R. japonicum cells with specificity, intensity and localization indistinguishable from FITC-SBA. Lectins from distinguishable from FITC-SBA. Lectins from three cultivars in sufficiently high concentration for study had molecular properties very similar to Chippewa SBA.Abbreviations FITC fluorescein isothiocyanate - IgG immunoglobulin G - SBA soybean agglutinin     

小麦大面积种植品种与骨干亲本的遗传差异解析

为了解小麦大面积种植品种和育种骨干亲本的遗传差异特点,利用分布于小麦全基因组的428个SSR标记对4个大面积种植品种和4个骨干亲本进行了比较分析。结果表明,8个材料间的遗传距离变异范围为0.460~1.126,平均0.876,其中骨干亲本间的平均遗传距离(0.955)高于大面积种植品种(0.718)。骨干亲本中检测到的等位变异数较大面积种植品种高16.4%,前者的平均等位变异(2.90)也略高于后者(2.43)。从不同基因组和染色体来看,骨干亲本在A、B和D基因组上及19对染色体(除了2D和6D)的平均等位变异均高于大面积种植品种。以上分析表明骨干亲本的遗传异质性高于大面积种植品种。进一步比较二者的分子差异,发现骨干亲本中有518个特有等位变异(在大面积品种中没有出现),其中Xwmc513和Xbarc59为骨干亲本共有位点,大面积品种中也检测到315个特有等位变异,其中Xp3029、Xwmc235、Xgwm518、Xgdm43、Xbarc146和Xcfd80为共有位点。前人研究表明骨干亲本的一些染色体区段传递给了大面积种植品种,在它们的形成中发挥了重要作用。本研究发现的特异位点可能是遗传研究中除了骨干亲本重要位点之外的一些需要重点关注的基因组区域,进一步研究有助于解析一个品种是被大面积推广利用或成为骨干亲本的形成原因。