西瓜绵腐病菌生物学特性研究

本文针对辽宁省西瓜生产上近年趋重发生的绵腐病,通过病原菌形态特征观察、柯赫氏法则证病试验、rDNA-ITS序列测定及分析,确定其致病菌为瓜果腐霉(Pythium a phanidermatum);并对该病原菌的主要生物学特性进行了研究.试验结果表明:菌丝在黄瓜煎汁培养基、蔗糖培养基、硫酸铵、甘氨酸培养基中生长最适;其生长最适温度35℃,最适pH为6～8;光照对菌丝生长影响较小;菌丝致死温度为51℃,10 min.产生孢子囊以菠菜煎汁培养基为最适,在麦芽糖、硝酸钾培养基中孢子囊产生量最大;产生孢子囊的最适温度为25℃、最适pH为8;光照培养产生孢子囊数量最多.     

In vitro techniques for genomic alteration in rice plants

Because of the explosive increase in world population, a sufficient food supply must be achieved by varietal improvement in the major cereal crops including rice. It is expected that new in vitro techniques incombination with conventional breeding methods may effectively raise the yield potential. On the other hand, there are many environmental problems to be solved world-wide such as, global warming, environmental pollution, ecological destruction, reduction in water supplies and so on. Therefore, it is necessary to rapidly develop new varieties for the future combining of higher yield potential with excellent grain quality, and resistance to both biotic and abiotic stresses for the promotion of sustainable agriculture. Although many efforts have been made to introduce useful traits from wild species to cultivated rice via hybridization, it is still difficult to overcome breeding barriers such as cross incompatibility and hybrid sterility and inviability in practical breeding. Now in vitro techniques are going to make it possible to use genetic manipulation and cell culture and fusion techniques to speed up the breeding process. For sustainable agriculture, it is important to utilize the useful genes from alien species. For this purpose, asymmetric protoplast fusions have already been used successfully to transfer disease resistance in Brassica napus. In this experiment, a high level of resistance to the rice blast disease was transferred from wild species through asymmetric fusions. It is also noted that manipulation of cytoplasmic genomes is possible through asymmetric fusions as shown in the induction of new cytoplasmic male sterility (CMS). This revised version was published online in August 2006 with corrections to the Cover Date.     

Geographical distribution of ribosomal DNA variation in taro, Colocasia esculenta (L.) Schott, in eastern Asia

Restriction fragment length polymorphism (RFLP) at the ribosomal RNA gene loci (rDNA) was investigated in 227 accessions of taro, Colocasia esculenta (L.) Schott, from China, Japan, Taiwan, and Vietnam. Eighteen different restriction fragment patterns of rDNA were observed. The results were largely consistent with a previous classification based on isozyme data. Some rDNA patterns were distributed extensively in the temperate zone from inland China to Japan. On the other hand, some other patterns ranged in coastal and/or insular areas from the tropical zone to the temperate zone (Japan). These geographical distributions may suggest two different routes for the introduction of taro into Japan: one from China,and the other most likely from Southeast Asia, via Taiwan and the Ryukyu Islands (southern Japan). This revised version was published online in August 2006 with corrections to the Cover Date.     

Somaclonal variation as a source of resistance to eyespot disease of sugarcane

After 10 years of evaluation in different locations with high levels of incidence of disease, a group of sugarcane somaclones derived from callus tissues was selected for eyespot resistance. Resistance evaluations of four somaclones were performed under field and laboratory conditions. The results confirmed the superiority of two somaclones, one resistant and one tolerant to eyespot disease. Restriction analysis of mitochondrial DN A revealed that the two somaclones had a different DNA organization which distinguished them both from each other and from the donor plant; the restriction profile was similar however to that of the resistant control done. Restriction patterns of a third somaclone, also resistant, were similar to those of the donor plant. Differences among the somaclones were also evident when using a maize ribosomal DNA probe.     

Development of conventional multiplex PCR method for discrimination between Dispharynx nasuta and Cheilospirura hamulosa (Nematoda: Acuariidae) parasitizing poultry

The poultry infections caused by Dispharynx nasuta and Cheilospirura hamulosa nematodes are difficult to be diagnosed by fecal examination because of their egg similarity. In this study, we analyzed DNA sequences of nuclear ribosomal 18S-ITS1-5.8S-ITS2-28S region of D. nasuta and C. hamulosa and developed conventional multiplex PCR method using species-specific primers for discriminating between the two species. The method amplified 455-bp and 319-bp fragments specific to D. nasuta and C. hamulosa, respectively, and did not produce them against the other chicken nematode species, Ascaridia galli, Oxyspirura mansoni, Heterakis gallinarum, Heterakis beramporia, and Heterakis indica, suggesting that the multiplex PCR is sensitive and available for species diagnosis.     

rDNA-ITS2应用于赤眼蜂分子鉴定的研究

本研究通过对拟澳洲赤眼蜂Trichoramma confusum，甘蓝夜蛾赤眼蜂T.brassicae，广赤眼蜂T.evanescens，食胚赤眼蜂T.embryophagum，及松毛虫赤眼蜂T.dendrolimi的6个地理种群的rDNA-ITS2进行克隆测序，又运用软件DNAStar的MegAlign程序对不同赤眼蜂属间，赤眼蜂属种间，同种不同地理种群之间以及同一赤眼蜂个体不同拷贝之间的ITS2序列的遗传分歧及相似性进行了分析。结果表明：赤眼蜂属与外群ITS2序列的遗传相似性很低，赤眼蜂属内不同种之间IT2序列保守性适中，种内或不同的地理种群之间以及同一个体不同ITS2拷贝间非常保守。说明ITS2序列可作为赤眼蜂种级水平分类鉴定的良好靶标序列。     

山东兔场皮肤真菌病病原rDNA-ITS区序列测定及分析

利用皮肤真菌核糖体内转录间隔区（Internal transcribed spacer,ITS）序列通用引物,对采自山东地区主要兔场的皮肤真菌病的16株分离菌进行了PCR扩增,ITS区的克隆、测序、序列变异及遗传进化关系分析。经与Gen-Bank核酸序列数据库数据比对结果表明：16株病菌分别为须癣毛癣菌（12/16,75%）、犬小孢子菌（2/16,12.5%）、石膏样小孢子菌（2/16,12.5%）;不同病原菌的5.8SrDNA序列高度保守,而ITS区的变异性则较高;对该区序列的聚类分析表明,不同种菌株ITS1比ITS2在碱基构成和序列长度上有更大变异;而种内各菌株的ITS1和ITS2在长度上均没有变异,碱基构成上存在微小的变异,可基于该区进行兔皮肤真菌的分类鉴定。该研究确定了兔皮肤病原PCR检测特异引物的靶序列,为兔皮肤真菌病病原的特异性分子鉴定提供了可靠的靶标,为兔皮肤真菌的科学分类提供了分子依据。     

28SrDNA PCR-RFLP分析在侧耳属系统发育研究中的应用

对侧耳属18个种52个菌株及3个其它属的菌株的28S rDNA 5‘端进行PCR扩增，得到长度约为1．46kb的片段。对该片段分别用7种限制性内切酶AluⅠ、BamHⅠ、HaeⅢ、HhaⅠ、HinfⅠ、MspⅠ、TaqⅠ酶切，结果表明，MspⅠ酶切片段多态性最高，AluⅠ对侧耳属无酶切多态性。聚类分析结果表明，菌株间的相似系数为0．569－1．000，在92％相似水平可将侧耳分为5大类：Ⅰ、红平菇和桃红侧耳；Ⅱ、鲍鱼菇和囊盖侧耳；Ⅲ、具核侧耳；Ⅳ、金顶侧耳；Ⅴ、其它所有供试侧耳。     

污水处理池环境细菌遗传多样性分析

以碱加热裂解法从山西农业大学污水直接和间接排放处理池自然水样中分离细菌总DNA ,以细菌 16SrRNA基因特异性引物扩增 16SrRNA基因片段。采用T -A克隆系统克隆分子量为 1339bp的PCR产物 ,构建了rDNA亚克隆文库。用三种识别六碱基的限制性内切酶两两组合消化重组质粒。共分析了两个处理池自然水样各 30个rDNA重组质粒 ,分别发现 4种和 8种细菌rDNA基因型。各基因型频率的分布变化比较大 ,最高和最低的频率分别为 0 2 5和 0 0 1。部分基因型频率间差异显著 ,遗传多样性指数分别为 0 4和 0 9。