陕西关中地区甘蓝型油菜白粉病的病原菌鉴定

为明确陕西关中地区甘蓝型油菜白粉病的病原种类,通过显微观察以及分子鉴定方法,对引起陕西关中地区油菜白粉病的病原进行鉴定。病原菌分生孢子梗简单不分枝,分生孢子顶生,无色,椭圆形或桶柱形,未发现闭囊壳。采用rDNA ITS通用引物扩增了病菌ITS区,对其产物进行测序及系统发育分析,5株菌与Erysiphe cruciferarum聚在一个独立的分枝上,支持率为96%。结合形态学和系统发育分析,鉴定陕西关中地区甘蓝型油菜白粉菌病原为Erysiphe cruciferarum。     

普通小麦rDNA的ITS区及其基因组起源

采用特异引物对普通小麦(Triticum aestivum L.) rDNA的ITS区片段进行PCR扩增并测序,通过邻接法聚类分析, 得到3种类型的扩增产物。结果表明,ITS区序列长度是602 bp,其中ITS1和ITS2分别有8个和20个变异位点,ITS区揭示的遗传分化距离变化范围为0~0.038,平均值为0.021。通过从GenBank搜索并下载普通小麦野生近缘种ITS序列与本研究获得的普通小麦ITS序列进行比对,并用MEGA、PAUP、PHYLIP软件分析,按Kimura-2参考模型计算分化距离,以旱雀麦(Bromus tectorum)为外类群邻接法构建聚类树。根据杂交后代具有亲本的ITS序列遗传特点,认为小麦形成较晚,尚未同步进化完全,从分子水平上为普通小麦是异源六倍体提供了证据。通过与其A、B、D基因组可能供体的ITS区序列进行比对分析发现各自有不同程度的变异,认为普通小麦在多倍体形成过程中发生了序列消除现象,结合我们提出的“同步进化”对于不同的基因或者说不同类型的DNA序列是不同步的假说,解释了无法找到真正供体的原因。综上所述,我们认为A、B、D基因组的原初供体可能分别是乌拉尔图小麦(T. urartu)、山羊草(T. speltoides)和节节麦(T. tauschii)。     

基于ITS序列探讨西瓜种下分化

【研究目的】对源自中国和非洲的15个西瓜Citrullus lanatus的核糖体基因内转录间隔区(in-ternal transcribed spacers,ITS)全序列进行比较分析。供试材料包括Mucosospermus亚种、Vulgaris亚种、源自中国的3个品种、源自加纳的3个品种和1个来自布基纳法索的品种。【结果】西瓜种内总变异位点27个,占总碱基数的5.93%,6个信息位点,占总碱基数的1.32%。不同品种西瓜的ITS序列全长455～473bp,G+C含量61.49%～63.41%。【结论】从ITS序列全长构建的系统树可以看出西瓜具有地理分化现象,中国西瓜和非洲西瓜分属不同分支。此研究对西瓜的引种、育种以及研究西瓜的地理演化都具有一定的指导意义。     

广州市异木棉属种质资源遗传评价

异木棉属(Ceiba)属的物种大都有很高的观赏价值,并被广泛引种栽培于世界各地的热带和亚热带地区。目前在华南地区广泛栽培的“美丽异木棉”是不是真正的美丽异木棉(C. speciosa),当初引进了一个物种还是多个物种都还存在疑问。本研究利用nrITS测序和ISSR分子标记两种方法来对广州市“美丽异木棉”172份种质资源进行了分析。基于nrITS序列分析表明,所分析的172个“美丽异木棉”样品中至少包括异木棉属三个物种以及它们之间的杂种,这三个物种分别是美丽异木棉(C. speciosa),C. insignis和C. crispiflora。通过比较基于nrITS序列鉴定的物种与对应个体的形态性状,干型、茎干上刺的有无、花瓣条纹多少、雄蕊筒附属物颜色和花期共五个性状与基于nrITS序列鉴定的物种存在明显的相关性,而花瓣形状、叶片边缘有无锯齿、花的大小和花瓣先端颜色与基于nrITS序列鉴定的物种无明显的相关性。ISSR分析表明,这些样品可以分为六个分支,同样这五个形态性状与基于ISSR的聚类有较好的相关性。本研究首次从分子角度揭示了华南地区栽培的“美丽异木棉”实际上包括异木棉属三个物种以及大量的物种间杂种。因此将所有栽培的个体直接称为美丽异木棉是不正确的,而应该结合其形态性状和分子数据来鉴定。“美丽异木棉”的遗传背景及这些种质资源遗传关系的解决为进一步开展优良品种选育和科学管理奠定了基础。     

Successful backcrosses of somatic hybrids between Sinapis alba and Brassica oleracea with the Brassica oleracea parent

Somatic hybrids between Sinapis alba (2n= 24) and Brassica oleracea (2n= 18) have been backcrossed with the B. oleracea parent. Whereas backcrosses with the diploid B. oleracea parent were unsuccessful, 344 BC₁ seeds could be obtained from inter-valence crosses with tetraploid B. oleracea (2n= 4x= 36). The investigated 96 BC₁ plants segregated for morphological traits and for fertility. They were backcrossed with diploid B. oleracea or self-pollinated, depending on their male fertility. The BC₁F₂ and BC₂ progenies segregated well for the morphological traits. Disturbances were observed especially in the generative phase (flower development and pollen fertility). Both male fertile and male sterile BC₁F₂ and BC₂ plants were obtained and backcrossed or self-pollinated with the B. oleracea parent. The presence of either one of the parental or the cybrid organelle genomes was detected. In the progenies, a stable maternal inheritance of the organelle genome patterns was observed. Isozyme analyses revealed polymorphism for the leucine aminopeptidase (LAP) which was used for the identification of S. alba genes in the progenies. Cytological investigations showed a clear differentiation between the BC₁F₂ and BC₂ plants. Whereas the BC₁F₂ plants possess large numbers of chromosomes ranging from 34 to 40, the BC₂ material was strongly reduced to chromosome numbers ranging from 20 to 22. Preliminary investigation of the meiosis suggests the possibility of introgressions of S. alba-DNA into the B. oleracea genome.     

Development of B-Genome Chromosome Addition Lines of B. napus Using Different Interspecific Brassica Hybrids

By interspecific hybridization within the genus Brassica, trigenomic haploids were produced and back-crossed four times with B. napus, variety ‘Andor’. From this material, monosomic B-genome chromosome addition lines were selected with the extra chromosome derived from three different B-genome sources, i.e., B. nigra (BB), B. carinata (BBCC), and B. juncea (AABB). After selfing and/or microspore culture, disomic addition lines were obtained. Meiotic behavior was studied of the trigenomic hybrids, the pentaploid BC₁ plants, and the monosomic addition lines. The addition lines were shown to possess cytological stability and good fertility.     

Feulgen-DNA densitometry of embryo sacs permits discrimination between sexual and apomictic plants in Paspalum simplex

The chromosomes of sexual diploid plants of Paspalum simplex were colchicine-doubled and the plant obtained were crossed with their aposporous natural tetraploid counterparts to generate a F1 population segregating for apomixis. Analysis of the DNA content during megagametogenesis indicated that although the nuclei of nucellus and developing embryo sacs were in both the G1 and G2 phases, polar nuclei and egg cells of mature embryo sacs tended to remain in the G1 phase. Because both meiotic and aposporous mature embryo sacs are of the 8-nucleated-type in P. simplex and are barely distinguishable, nuclear DNA content of polar nuclei was used to distinguish apomictic and sexual phenotypes and confirmation obtained by progeny testing. This revised version was published online in August 2006 with corrections to the Cover Date.     

Ploidy reduction in blackberry

Polyploidy in blackberries and ploidy differences between Rubus species are obstacles to the efficient introduction of valuable germplasm, both intra- and interspecific, into blackberry breeding programs. Expansion of the germplasm base would be facilitated by reducing the ploidy level of blackberry cultivars to the diploid level. In this report selection of twin seed, interspecific hybridization, and pollen irradiation were compared as methods in the recovery of dihaploids from tetraploid blackberry cultivars. One dihaploid was obtained through selection of twin seed and several were obtained following interspecific hybridization. The infrequency of twinning and difficulty in detecting twin seed in Rubus reduced the efficiency of this method. The efficiency with which dihaploids could be obtained following interspecific hybridization varied with the pollen parent. Reduced seed set and seed quality following pollinations with respectively R. parvifolius and R. hirsutus could be used to advantage in the recovery of dihaploids from blackberries. Ploidy reduction in several tetraploid blackberry cultivars was obtained following pollinations with 100 and 150 kR gamma irradiated pollen. Most of the seedlings obtained at the 50 kR dosage were aneuploid. Pollen irradiation at 150 kR was the most efficient method of obtaining dihaploids from tetraploid blackberries. Twenty percent of the seedlings obtained following this treatment were dihaploid.     

流式细胞术在植物学研究中的应用——检测植物核DNA含量和倍性水平

流式细胞仪作为高效的检测工具,在植物学研究的多个领域都发挥了重要作用。兰州大学干旱与草地生态教育部重点实验室分子生态所通过大量的植物流式细胞术实验,针对检测植物核DNA含量和倍性水平,总结出一套详细通用的实验方法。同时着重阐述了各个实验环节的关键点。分析因碎片过多而导致实验失败的原因,并提供了切实可行的解决方法。对今后检测各种植物具有重大指导意义,同时也促进了流式细胞术在植物学研究中的应用。     

The Gene Pools of the Grasspea (Lathyrus sativus L.)

Interspecific hybridization between the grasspea, Lathyrus sativus, and 15 wild species in Section Lathyrus is reported. Only two species, L. amphicarpos and L. cicera produced viable F¹ hybrids with low fertility when crossed with L. sativus as male parent. Crosses with six other species produced pods following pollination when L. sativus was the male, but seedlings were inviable, seeds did not germinate or pods were empty or had totally shrivelled seeds. When L. sativus was the female parent, only one cross with L. gorgoni produced an F¹, but the seedling was inviable. The germplasm resources of the grasspea are identified, with L. amphicarpos and L. cicera placed in the secondary gene pool and the other species in the tertiary gene pool. The definition of these germplasm resources is discussed in terms of grasspea improvement through plant breeding.     

Relationships between African species of the genus Cucumis L. Estimated by the production,vigour and fertility of F1 hybrids

Summary The production, vigour, and fertility of F₁ hybrids between nine African species of the genus Cucumis L. were studied as a measure of the relationships between the species. Hybrid plants were obtained from 29 out of the 72 possible cross combinations. Two F₁ hybrids died as seedlings, and 27 hybrids were raised to maturity. Pollen production and stainability varied greatly amongst these hybrids, as did fruit and seed set following self pollination and backcrossing with either parental species. The fruit shape of the hybrids was always intermediate between that of both parental species.Two species appeared to be closely related: C. prophetarum L. and C. anguria var. longipes A. Meeuse. Most other species produced highly to moderately fertile F₁ hybrids with at least one other species. C. metuliferus Naud. produced only sterile hybrids with C. zeyheri Sond. 2x. The results sustain the recent taxonomic classification of the genus (Jeffrey, 1980).     

Critical Discussion on Abortive Interspecific Crosses in Brassica

In most interspecific hybridization among diploid Brassica species (n = 8, 9, 10), few or no hybrids are obtained, and the three crosses of tetraploid (n = 17, 18, 19) by diploid species are usually only partially successful, especially in one of the reciprocal crosses. Such a cross-incompatibility complex is explained in this paper by a polar-nuclei activation (PNA) hypothesis which proposes two reversible functions, a normal reproduction and a sexual barrier, of double fertilization in higher plants. The first, i.e. the relative activating value (AV) of diploid species, was estimated as 1.0–3.5, whereas that of tetraploid species was 2.7–5.2. In addition, crosses with a polar nuclei activation index (AI) of about 15–87 % were compatible but those beyond the two limits were incompatible, 50 % of those showing normal seed development after self-pollination.