Genetic variation of the durum wheat landrace Haurani from different agro-ecological regions

The durum wheat landrace Haurani (Triticum durum Desf.) is grown under contrasting climatic regions of Syria from Deir Ezzor, in the North-East (230 m altitude, 150 mm mean annual rainfall), to Qunaytra, in the South-West (1060 m altitude, 825 mm mean annual rainfall). In order to assess the genetic variation between and within Haurani populations, samples from eight provinces of Syria (Daraa, Damascus, Qunaytra, Deir Ezzor, Hassakeh, Aleppo, Homs and Hama) were analysed by RFLPs and seed storage proteins of glutenin subunits as markers. The analyses showed the presence of genetic polymorphisms in all populations with the highest values in those from Homs and Hassakeh. Moreover, the results point out differences in genetic distances between populations; some populations were further apart, such as Damascus and Aleppo, whereas others were closer to each other, for instance Homs and Hama. Cluster analysis identified two distinct groups of populations, characterized by geographical proximity, with similar rainfall and altitude. It is suggested that the similarity of landraces at locations close to each other might be the result of more frequent seed exchanges between farmers or of gene flow due to 5% estimated outcross rate of Haurani.     

A comparison of crop data measured by two commercial sensors for variable-rate nitrogen application

Nitrogen (N) fertilizer rates applied spatially according to crop requirements can improve the efficiency of N use. The study compares the performance of two commercial sensors, the Yara N-Sensor/FieldScan (Yara International ASA, Germany) and the GreenSeeker (NTech Industries Inc., Ukiah, California, USA), for assessing the status of N in spring wheat (Triticum aestivum L.) and corn (Zea mays L.). Four experiments were conducted at different locations in Quebec and Ontario, Canada. The normalized difference vegetation index (NDVI) was determined with the two sensors at specific growth stages. The NDVI values derived from Yara N-Sensor/FieldScan correlated with those from GreenSeeker, but only at the early growth stages, where the NDVI values varied from 0.2 to 0.6. Both sensors were capable of describing the N condition of the crop or variation in the stand, but each sensor had its own sensitivity characteristics. It follows that the algorithms developed with one sensor for variable-rate N application cannot be transferred directly to another sensor. The Yara N-Sensor/FieldScan views the crop at an oblique angle over the rows and detects more biomass per unit of soil surface compared to the GreenSeeker with its nadir (top-down) view of the crop. The Yara N-Sensor/FieldScan should be used before growth stage V5 for corn during the season if NDVI is used to derive crop N requirements. GreenSeeker performed well where NDVI values were >0.5. However, unlike GreenSeeker, the Yara N-Sensor/FieldScan can also record spectral information from wavebands other than red and near infrared, and more vegetation indices can be derived that might relate better to N status than NDVI.     

PCR Marker-based Analysis of Wild and Cultivated Yams (<Emphasis Type="Italic">Dioscorea</Emphasis> spp.) in Nigeria: Genetic Relationships and Implications for <Emphasis Type="Italic">ex situ</Emphasis> Conservation

Reliable characterization of the variation among wild and cultivated yams in Nigeria is essential for improved management and efficient utilization of yam genetic resources. RAPD and double stringency PCR (DS-PCR) analyses were used to investigate genetic relationships and the extent of redundancy among 30 accessions of two cultivated, and 35 accessions of four wild yam species collected from Nigeria. Twenty-five selected random decamer and two microsatellite primers were used individually and in combination to generate DNA profiles for each accession of the six Dioscorea species. The number of amplified fragments varied from 7 to 18 fragments per primer/primer combination. Different levels of intraspecific genetic diversity were found, with Dioscorea rotundata Poir. being the most variable. Based on identical profiles for the RAPD and DS-PCR primers, 12 duplication groups consisting of a total number of 37 accessions were observed in the present study. An UPGMA analysis grouped the majority of plants according to the species. Cultivated yams belonging to the D. cayenensis–rotundata species complex, which were classified into seven morphotypes/varietal groups, could be clearly separated into two major groups corresponding to D. rotundata Poir. and D. cayenensis Lam. D. cayenensis cultivars exhibited a low level of intraspecific variation and were genetically close to the wild species Dioscorea burkilliana J. Miège. D. rotundata cultivars classified into six varietal groups showed a high degree of DNA polymorphism and were separated into two major groups that appeared most closely related to Dioscorea praehensilis Benth. and Dioscorea liebrechtsiana de Wild. We propose, based on these results, that cultivars classified into D. cayenensis should be considered as a taxon separate from D. rotundata. The implications of intraspecific variability for the ex situ conservation of wild and cultivated yam germplasm in Nigeria are discussed.     

山西省新疆杨造林中其个体基因变异的研究

新疆杨(Populus bolleana LAUCHE)是山西省北部乃至中国西北部重要的阔叶树造林树种,但目前发现只有雄性植株,它很可能是一个或几个无性系通过无性繁殖而大规模传播开来,基因变异狭窄,会给造林带来巨大的潜在危险。于2004年到2005年在山西省境内随机采集59个样树,在德国爱博斯瓦尔德大学(FH-Eberswalde)的生态实验室进行了同工酶分析。分析结果显示,在山西省境随机采样的59个新疆杨树中,88%的被猜测为是一个或同样的无性系。初步证实山西省境内的新疆杨造林基因变异有限,这就是说在山西境内新疆杨的造林潜在着巨大的风险。同时就避免或降低这种风险的可能性进行讨论。     

Genetic Relationship between <Emphasis Type="Italic">Castanea sativa</Emphasis> Mill. Trees from North-western to South Spain Based on Morphological Traits and Isoenzymes

This study is focused in the main chestnut growing areas from north- to south-western Spain. We studied 50 accessions corresponding to 22 cultivars named by local growers; 11 from Andalucía, 9 from Castilla-León, and 2 from Extremadura. These were compared with 22 types classified previously in Galicia (82 accessions). Ten morphological traits and five isoenzyme systems were used to classify them and establish genetic relationships. A lower genetic variability has been found in Extremadura (middle Spain) and Andalucía (south) than in Galicia (north western) which may be because of the lower importance of the crop in those areas and the geographic barriers between them. Galicia could be the origin of the types found in Castilla-León, Extremadura, and south-western Andalucía, and the types found in Central Andalucía were closer to those found in Castilla-León and Extremadura. Most accessions studied (117/132) could be classified positively, making 37 out of 44 cultivars found from northern to southern Spain. Three groups of synonymies were found in Castilla-León: ‘Brava’ and ‘Negral’, ‘Gallego’ and ‘Injerto’, and ‘Rapega’ and ‘Verdello’. Most of the Spanish types have been propagated as a principal clone. Variability within the types is important and must be considered to select the best clones as cultivars.     

Genomic, protein and antigenic variability of mycoplasma bovis

Restriction endonuclease analysis (REA) with three enzymes SmaI, PstI, BamHI- was used to identify 13 different genomic groups among 37 Mycoplasma bovis strains. One genomic group was comprised of 14 strains. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) patterns for one strain chosen from each genomic group and an international reference strain PG45 were all similar. Antigenic variability in M. bovis species was investigated by immunoblotting, using serum from a calf that had been naturally infected with M. bovis and three M. bovis-specific monoclonal antibodies — mAbs N₂, I₂ and 5D7. Twenty M. Bovis field strains were tested, comprising one from each genomic group, six from the same genomic group and the reference strain. Antigenic profiles obtained with calf serum differed markedly one from the other, the heterogeneity being equally great among the strains belonging to the same genomic group as those coming from different groups. A stable antigen common to 164 out of 168 strains was detected by mAb N₂, whilst with mAbs I₂ and 5D7, two different membrane antigenic systems were demonstrated that were strikingly variable. These variations in expression occurred not only from one strain to another, but also within the same lineage of clones from a single cell.     

Analyzing isolate variability of Macrophomina phaseolina from a regional perspective

Sexton, Z.S., Hughes, T.J., and Wise, K.A. 20XX. Analyzing isolate variability of Macrophomina phaseolina from a regional perspective. Crop Protection. XX:XXXX. Charcoal rot of soybean (Glycine max L.), caused by Macrophomina phaseolina (Tassi) Goid, has been reported more frequently in the north–central United States in recent years. Growth of isolates collected from the northern and southern U.S. was compared in vitro under various incubation temperatures, and isolate pathogenicity was assessed on cultivars adapted to each region. Results indicate that northern isolates had increased growth at 15 °C compared to isolates from southern states, while southern isolates grew 23% more at 40°C compared to northern isolates. Isolates from both regions were pathogenic on charcoal rot resistant and susceptible cultivars adapted for each region. This is the first research to suggest the importance of screening germplasm under regional environmental conditions and with local or regionally adapted isolates when evaluating cultivar resistance to charcoal rot.     

50个大菊品种形态学性状比较分析

以麻城市五脑山林场菊花种质资源圃中50种大菊品种为研究对象,采用田间随机区组实验设计,对64个形态性状进行了测定,并进行了一致性及变异性分析、主成分分析和聚类分析,结果表明:在所有性状中有59个性状变异系数大于15％;前7个主成分对变异的贡献率达81.45％,其中特征量较大的花部性状对大菊品种分类具有较大的影响;通过聚类分析可将50份大菊种质资源分为4类,形态差异明显;株型可作为大菊分类的一个重要指标.     

利用土壤切片的数字图像定量评价土壤孔隙变异度和复杂度

研究结果表明 :利用土壤切片的数字图像 ,以孔隙周长和面积为基础数据 ,可以定量评价小尺度上的孔隙变异度 ,也可以对孔隙复杂度进行研究 ;土壤孔隙在mm尺度上也具有较高的变异度和复杂度 ;粒径 1～ 3mm和粒径 <2cm的重组土壤的孔隙在 2D空间多呈现网络状 ,而原状土壤的孔隙则多呈不规则的枝状或椭圆状 ;不同处理及不同土壤类型之间在孔隙周长、孔隙度以及孔隙变异度和复杂度方面存在不同程度的差异。     

蒙古栎材积生长的变异性研究

[目的]研究蒙古栎材积生长的变异性。[方法]对7株蒙古栎材积生长的株内和株间变异性进行分析,拟合经验生长方程和理论生长方程。[结果]蒙古栎材积生长株间变异在幼龄期不明显,随时间增加而增大,生长速率稳定后,差异性存在且稳定增加。蒙古栎材积生长在株内的变异性较小,幼龄期至生长期生长速率加快,变异性有所增加,生长稳定后,差异性存在且稳定。[结论]蒙古栎在生长过程中材积变化受外界因素的干扰较小,可较准确预测未来几年的材积生长状况。