Characterization of Fusarium spp. responsible for causing dry rot of potato in Great Britain

A 3-year survey was undertaken to establish the relative frequency of different Fusarium spp. present as inoculum on potato tubers collected from four regions of Great Britain. A total of 219 samples (comprising 10 950 tubers) were collected from the 2000, 2001 and 2002 crops and processed to recover dry rot-producing isolates. In total, 228 isolates of Fusarium spp. were recovered. Most (94·7%) of these isolates were attributed to one of four Fusarium species: F. coeruleum, F. avenaceum, F. culmorum and F. sambucinum (formerly F. sulphureum) . The incidence of the combined Fusarium spp. increased the further south the crops had been grown. Fusarium coeruleum was the most commonly isolated species in each survey year, comprising 37 to 52% of the total Fusarium species. Selected isolates of each species were evaluated for their ability to produce rots in potato tubers. Fusarium sambucinum was a more aggressive pathogen than the other Fusarium species in eight out of 10 cultivars. Fusarium avenaceum and F. culmorum were relatively weaker pathogens. However, these species were aggressive on some cultivars, notably Hermes. The selected isolates were also assessed for their sensitivity to the fungicides thiabendazole and imazalil. Using in vitro tests, 65% of F. sambucinum isolates were resistant to thiabendazole and 7% of F. avenaceum isolates were resistant to imazalil. Tubers treated with imazalil yielded a higher proportion of isolates of F. avenaceum than those that were untreated. Similarly, a higher proportion of F. sambucinum isolates were recovered from tubers treated with thiabendazole than from those that were not treated.     

小麦赤霉病穗组织中黄色镰刀菌和DON毒素的定量分析

为阐明小麦赤霉病穗组织中黄色镰刀菌Fusarium culmorum(简称Fc)与毒素产生之间的关系.分别用TaqMan探针实时定量PCR和ELISA法,对接种4天后的17个小麦品系穗组织中的FcDNA和脱氧雪腐镰刀菌烯醇(DON)含量进行了测定.在Fc DNA定量检测中,TaqMan探针实时PCR技术具有高度的稳定性和可重复性.不同小麦品系的Fc DNA含量差异显著,感病品种比抗病品种高100倍左右;DON含量也不相同,Fc生物量的增加伴随着DON产量的提高,两者之间存在对数关系(y=19758 lnx-111230).菌量较低时,DON含量相对较大;而菌量较高时,DON含量相对偏低.     

Flavescence dorée phytoplasma titre in field‐infected Barbera and Nebbiolo grapevines

Flavescence dorée phytoplasma (FDP) titre in two red grapevine cultivars, Barbera and Nebbiolo, was measured over the vegetative seasons of two consecutive years in two vineyards of the Piemonte Region (northwestern Italy), with a double absolute quantification of FDP cells and grapevine DNA in real‐time PCR. The relationships of pathogen concentration to cultivar susceptibility and symptom severity were investigated. FDP titre was always higher in cv. Barbera than in cv. Nebbiolo infected vines, and this difference was significant at early and late summer samplings of 2008 and at early summer sampling of 2009. A seasonal trend in FDP concentration (low in spring, high in early summer and intermediate in late summer) was conserved for cvs Barbera and Nebbiolo in both years and vineyards. Considering both cultivars and years from both vineyards, a significant positive correlation between FDP concentration and symptom severity was found in the spring samples. Regarding the FDP strains (‐C or ‐D), no differences in pathogen titres were detected for either cultivar. Similarly, the presence of another grapevine yellows phytoplasma, bois noir, a subgroup 16SrXII‐A phytoplasma, in mixed infection with FDP strains had no effect on FDP concentration. These results demonstrate for the first time that grapevine cultivars with different susceptibility to FDP support different pathogen titres.     

基于Hege16的水稻脱粒及其损伤影响因素试验研究

用破碎率、内部损伤率、平均内部损伤度来定量评价稻谷的损伤程度,并在实验室用Hege 16脱粒机进行水稻脱粒试验,分析了脱粒元件线速度、凹版间隙、喂入量等因素对水稻籽粒脱粒损伤以及装置性能指标的影响。进行了单因素试验与正交试验,正交试验结果表明:凹版间隙对于损失率、破碎率、内部损伤率影响较显著,脱粒线速度对平均内部损伤度影响较显著,喂入量影响不显著;得到脱粒试验的最优参数组合为凹版间隙13 mm,脱粒元件线速度18 m/s,喂入量1. 6 g/s。     

Molecular diagnosis and direct quantification of cereal cyst nematode (Heterodera filipjevi) from field soil using TaqMan real-time PCR

Heterodera filipjevi continues to be a major threat to wheat production worldwide. Rapid detection and quantification of cyst nematodes are essential for more effective control against this nematode disease. In the present study, a TaqMan-minor groove binder (TaqMan-MGB) probe-based fluorescence quantitative real-time PCR (qPCR) was successfully developed and used for quantifying H. filipjevi from DNA extracts of soil. The primers and probe designed from the obtained RAPD-SCAR marker fragments of H. filipjevi showed high specificity to H. filipjevi using DNA from isolates-confirmed species of 23 Heterodera spp., 1 Globodera spp. and 3 Pratylenchus spp. The qPCR assay is highly sensitive and provides improved H. filipjevi detection sensitivity of as low as 4^–3 single second-stage juvenile (J2) DNAs, 10^–3 female DNAs, and 0.01 μg μL^–1 genomic DNAs. A standard curve relating to the threshold cycle and log values of nematode numbers was generated and validated from artificially infested soils and was used to quantify H. filipjevi in naturally infested field soils. There was a high correlation between the H. filipjevi numbers estimated from 32 naturally infested field soils by both conventional methods and the numbers quantified using the qPCR assay. qPCR potentially provides a useful platform for the efficient detection and quantification of H. filipjevi directly from field soils and to quantify this species directly from DNA extracts of field soils.     

水稻离体叶片纹枯病接种样品菌量检测方法研究

利用qPCR方法对水稻离体叶片纹枯病接种材料进行纹枯病菌含量的检测,从而对水稻发病程度进行定量分析。各水稻品种接种样品的纹枯病菌DNA含量,从低到高的顺序为:YSBR1、徐稻3号、台北309、泰粳394和Lemont。通过对接种实验条件的精确控制,离体叶片的病斑扫描,以及相对病斑面积的统计分析,验证了关于病害严重程度的qPCR检测结果。大田接种试验中,YSBR1、Lemont和泰粳394的平均病级呈显著差异;这进一步证明,通过纹枯病菌DNA的qPCR方法,能够快速有效地定量检测不同水稻品种的纹枯病抗性差异。该研究可为量化纹枯病发病程度、评价水稻品种的抗性水平及进行纹枯病的早期预报,提供有效的检测手段。     

基于数量化理论Ⅲ的滑坡变形组合预测研究

[目的]探讨基于数量化理论Ⅲ的组合预测模型在滑坡变形组合中的适用性,为滑坡变形组合预测提供新的思路。[方法]选取GM(1,1)、支持向量机、BP神经网络及MC预测作为滑坡变形的单一预测模型,并利用数量化理论Ⅲ分析单项预测的相对误差区间的重要性,进而确定区间权重,再结合预测误差确定的组间权重,综合确定组合预测的权值。[结果]组合预测结果相对误差的平均值为1.1%,方差为0.16。[结论]组合预测较单一预测模型的预测精度及稳定性都有较大的提高。     

廊道式建设工程生态影响评价范围

廊道式建设工程深刻影响沿线的区域生态与环境,定量化开展廊道式建设工程生态影响评价具有重要意义。科学地确定廊道式建设工程生态影响的空间范围,是客观、准确评价工程建设生态影响的前提。目前,廊道式建设工程生态影响评价难以确定合理、标准化的评价范围,同时,存在评价因素单一和缺乏针对性等问题。通过分析不同类型的廊道式建设工程生态影响特征,归纳了典型廊道式建设工程生态影响的评价范围及其确定方法,结合国内外廊道式建设工程生态影响评价范围的相关规定,建议通过类比分析、整合分析、样线法、缓冲区分析等多种方法相结合,分区域、分生态因子确定廊道式建设工程生态影响的评价范围。