抗白粉病小偃麦异代换系的细胞学和RAPD鉴定

利用细胞学和RAPD方法,对从长穗偃麦草与普通小麦复合杂交后代中选育的抗白粉病小麦种质系山农87074－526和山农87074－551进行了鉴定。结果表明,两种质系的根尖细胞染色体数目均为2n=42,花粉母细胞减数分裂中期I（PMC MI）染色体构型为2n=21Ⅱ;二者杂交F1 PMC MI染色体构型亦为2n=21Ⅱ,两种质系分别与小麦中国春的杂种F1 PMC MI染色体构型均为2n=20Ⅱ 2I,说明两种质系为相同的双体异代系。在苗期和成株期两种质系对白粉病15号菌种均表现免疫,其白粉病抗性为显性,并且来自长穗偃麦草,抗白粉病基因位于它们所含的偃麦草染色体上。从80个随机引物中,筛选出2个引物OPE13和OPH15能在两种质系中稳定地扩增出长穗偃麦草亲本的特异DNA片段。     

野生二粒小麦抗白粉基因的转移及其RAPD分析

白粉病已成为威胁我国小麦稳产的重要病害之一。寻找并使用新的白粉病抗源成为当今抗白粉病育种的关键。报道野生二粒小麦抗白粉病基因向普通小麦转移,无论是正交还是反交,用普通小麦作轮回亲本,随着回交代数增加,抗性单株选择难度加大,从正,反单交F6中均获得了稳定抗病株系,同时,研究利用RAPD方法对小麦-野生二粒小麦抗白粉病和感白粉病9个衍生系进行了分析研究。研究结果表明,5个随机引物（OPH-07,OPQ-08,OPQ-16,OPQ-19,OPZ-16）能在抗,感9个衍生系中分别扩增出普通小麦所没有的野生二粒小麦特异带型;其中OPH-07340bp和OPQ-19900bp为抗病系的特征带。     

抗白粉病小麦——中间偃麦草异附加系的细胞学和RAPD鉴定

利用细胞学和ＲＡＰＤ技术,对从小麦与中间偃麦草杂种后代中选育的抗白粉病异附加系ＤＡＬ６６进行了鉴定。结果证明ＤＡＬ６６根尖细胞染色体数为４４,花粉母细胞减数第一分裂中期（ＰＭＣ ＭＩ）杂色体模型为２ｎ＝２２Ⅱ。对ＤＡＬ６６及其双亲进行ＲＡＰＤ分析,从４０个随机引物中筛选出１个特异引物（ＯＰＥ－０２）能够稳定地扩增出特异带型。     

嫁接对辣椒根际土壤环境的影响及其与抗病性和产量的关系

以‘卫士’(WS)和‘部野丁’(BYD)辣椒为砧木,‘新丰2号’(XF)辣椒为接穗嫁接,以‘新丰2号’自根嫁接辣椒(XF/XF)为对照(CK),研究嫁接对辣椒根际土壤微生物量、物理性质、养分含量及土传病害和产量的影响.结果表明: 嫁接辣椒新丰/卫士(XF/WS)与新丰/部野丁(XF/BYD)根际土壤的真菌和放线菌数量较多,放线菌比例较大;定植60 d时,嫁接辣椒根际土壤过氧化氢酶(CAT)和过氧化物酶(POD)活性显著高于CK;定植90 d时,XF/WS根际土壤磷酸酶、蔗糖酶、脲酶、硝酸还原酶(NR)活性显著高于CK;此外,嫁接辣椒根际土壤浸提液中的烃类化合物增多,XF/WS和XF/BYD根际土壤N、P、K含量显著低于CK,根际土壤电导率(EC)略高,XF/WS的pH显著高于CK,而XF/BYD与CK差异不显著.说明嫁接可优化辣椒根际土壤环境,增强其对土传病害的抗性,XF/WS和XF/BYD的产量分别比CK增加40.8%和28.7%.     

Identification of powdery mildew (Erysiphe graminis sp. tritici) and take-all disease (Gaeumannomyces graminis sp. tritici) in wheat (Triticum aestivum L.) by means of leaf reflectance measurements

The ability to identify diseases in an early infection stage and to accurately quantify the severity of infection is crucial in plant disease assessment and management. A greenhouse study was conducted to assess changes in leaf spectral reflectance of wheat plants during infection by powdery mildew and take-all disease to evaluate leaf reflectance measurements as a tool to identify and quantify disease severity and to discriminate between different diseases. Wheat plants were inoculated under controlled conditions in different intensities either with powdery mildew or take-all. Leaf reflectance was measured with a digital imager (Leica S1 Pro, Leica, Germany) under controlled light conditions in various wavelength ranges covering the visible and the near-infrared spectra (380–1300 nm). Leaf scans were evaluated by means of L*a*b*-color system. Visual estimates of disease severity were made for each of the epidemics daily from the onset of visible symptoms to maximum disease severity. Reflectance within the ranges of 490₇₈₀ nm (r² = 0.69), 510₇₈₀nm (r² = 0.74), 516₁₃₀₀nm (r² = 0.62) and 540₁₃₀₀ nm (r² = 0.60) exhibited the strongest relationship with infection levels of both powdery mildew and take-all disease. Among the evaluated spectra the range of 490₇₈₀nm showed most sensitive response to damage caused by powdery mildew and take-all infestation. The results of this study indicated that disease detection and discrimination by means of reflectance measurements may be realized by the use of specific wavelength ranges. Further studies have to be carried out, to discriminate powdery mildew and take-all infection from other plant stress factors in order to develop suitable decision support systems for site-specific fungicide application.     

Highly efficient in vitro proliferation and genetic stability analysis of micropropagated Ceropegiaevansii by RAPD and ISSR markers: A critically endangered plant of Western Ghats

Ceropegiaevansii McCann (family: Asclepiadaceae), a critically endangered plant of Western Ghats has acquired significant importance due to its medicinal implications, edible tubers, and ornamental flowers. This study deals with the optimization of axillary bud proliferation using nodal explants followed by genetic stability analysis of regenerants. Maximum number of shoots (11.6 ± 1.1) was observed on the Murashige and Skoog (MS) medium supplemented with 6-benzylaminopurine (4.0 mg/l) and indole-3-acetic acid (0.3 mg/l) with 85% shoot multiplication frequency. In vitro-grown shoots were rooted best in 1/2 MS medium supplemented with indole-3-butyric acid (1.0 mg/l) with an average of 10.3 ± 0.9 roots per shoot and 92% rooting frequency. Plantlets were acclimatized best (90%) in a mixture of sterile soil, sand, and coco peat (1:2:1). Micropropagated plants were subjected to random amplified polymorphic DNA and inter simple sequence repeat markers analyses. Collectively, 759 bands were generated which were monomorphic and similar to the mother plant. Findings of this study are the first report on micropropagation and assessment of genetic stability of micropropagated plantlets in C. evansii which suggests that axillary shoot proliferation can safely be used as an effective tool for propagation and conservation of C. evansii.     

大棚黄瓜霜霉病气候生态防治方法研究再报——高温控制与病情和产量关系及其防治指标

本文采用田间温度控制试验资料,用数理统计的方法分析高温控制范围、控制时间和控制频率与大棚黄瓜霜霉病的发生期、流行期、发生程度以及产量的关系,并建立了统计相关模式,确定了高温控制生态防治方法的技术指标。最高温度、高温控制时间和控制频率这3个主要指标与病情和黄瓜产量的关系非常密切,最高气温每升高1℃,发病期和流行期将推迟3—5天,病叶率降低13—15％,黄瓜产量可增长10％左右。在一定范围内,控制时间越长,频率越高,则发病期和流行期越晚,病情越轻,产量越高。研究证明,高温控制方法是一个有效的生态防治方法,具有明确的气候生态学依据。     

Location and mapping of the powdery mildew resistance gene MlRE and detection of a resistance QTL by bulked segregant analysis (BSA) with microsatellites in wheat

Powdery mildew (Blumeria graminis f. sp. tritici) is one of the most damaging diseases of wheat (Triticum aestivum). The objective of this study was to locate and map a recently identified powdery mildew resistance gene, MlRE, carried by the resistant line RE714 using microsatellites uniformly distributed among the whole genome together with a bulked segregant analysis (BSA). The bulks consisted of individuals with an extreme phenotype taken from a population of 140 F₃ families issued from the cross between RE714 (resistant) and Hardi (susceptible). The population had been tested with three powdery mildew isolates at the seedling stage. Qualitative interpretation of the resistance tests located the MlRE gene on the distal part of the long arm of chromosome 6A. A subsequent quantitative interpretation of the resistance permitted us to detect another resistance factor on a linkage group assigned to chromosome 5D, which was constructed with microsatellites for which a polymorphism of intensity between bulks was observed. This quantitative trait locus (QTL) explained 16.8– 25.34% of the total variation. An interaction between both the resistant factor (MlRE and the QTL) was found for only one of the isolates tested. This study shows the advantage of making a quantitative interpretation of resistant tests and that the use of microsatellites combined with BSA is a powerful strategy to locate resistance genes in wheat. Received: 30 August 1999 / Accepted: 11 November 1999     

Patterns of genetic variation detected by RAPDs suggest a single origin with subsequent mutations and long-distance dispersal in the apomictic fern Dryopteris remota (Dryopteridaceae)

Debates on speciation processes in pteridophytes have revived. In order to study the evolutionary origin of an apomictic fern species, we investigated the genetic variation in the strictly agamosporous Dryopteris remota. We determined the genotypes of 22 individuals from many different locations within the species' European distribution and of 20 individuals from a Swiss population. A previous study on isozyme variation showed no intraspecific genetic variation in a similar sample set (Schneller and Holderegger, 1994, American Fern Journal 84: 94-98). In contrast to this, four out of 12 random amplified polymorphic DNA (RAPD) primers tested revealed low genetic diversity among individuals of D. remota from different locations. Intrapopulational genetic variation was also very low, but in the single population studied, a unique multiband genotype could be detected. The geographic distribution of genetic variation found in D. remota was best explained by the assumption of a single origin, the accumulation of somatic mutations during spread, and occasional, but effective, events of dispersal over large distances. The present study thus stresses the importance of long-distance dispersal in evolutionary processes and biogeography of ferns.