不同碳源氮源对腐霉菌株生长的影响

在喀麦隆芋芳根涡病病原研究中，测定了不同碳源、氮源对分离自喀麦隆芋艿田间及来自中国的腐霉菌株生长习性的影响。实验结果表明，除了钟腐霉（Ｐｙｔｈｉｕｍｖｅｘａｎｓ）菌株只能吸收葡萄糖、果糠而不能吸收蔗糖外，其余腐霉菌株均能利葡萄糖、果糖、蔗糖作为碳源。所有试验菌株均不能利用半乳糖、麦芽糖及可溶性淀粉。钟腐霉菌株之形态特征与特殊碳源营养的相关性显示了用碳源作为菌株鉴定辅助标准的可行性，氮源营养试验结果表明，所有腐霉菌株均能利用四种氮源，根据不同氮源对菌丝生长的影响，依次为Ｌ－天门冬氨酸，Ｌ－精氨酸，硝酸铵，硝酸钾。     

草地类型梯度分析

紫泥泉地区位于天山北坡低山带，具有代表性的冬春秋放牧场。本文应用数量分类（ＴＷＩＮＳＰＡＮ）、排序（ＤＣＡ）和回归分析方法研究了草地类型的分类及其分布的梯度规律。研究结果表明：该地区的草地类型按传统分类划分出１８个型，ＴＷＩＮＳＰＡＮ分类结合ＤＣＡ排序归纳出８个型，其中６个型为地带性草地类型，２个型为非地带性草池类型；地带性草地类型沿水热梯度分布，非地带性草地类型沿质地梯度分布。     

ITS—RFLP分析进行昆虫病原线虫斯氏属和异小杆属的分类鉴定

本研究通过PCR扩增和六种限制性内切酶（AluⅠ，HinfⅠ，MboⅠ，RsaⅠ，HaeⅢ和PvuⅡ）酶切，对国内害虫防治上常用的几种昆虫病原线虫，包括斯氏属S.car-pocapsae,S.feltiae和S.glaseri以及异小杆属H.bacteriophora,H.zealandica,H.indicus和H.megidis等8个品系rDNA-ITS进行分析。建立起可以区分各线虫种的标准RFLP图谱。该方法快速简便，稳定可靠，需要的样品量少。可以用于新鲜的，或冻存的样品，甚至分析单条的线虫，不仅可进行昆虫病原线虫的快速分类鉴定。而且进一步可以应用于线虫田间释放的辅助监测。实际田间感染率的测定和线虫毒力的比较。     

Orobanche species and population discrimination using intersimple sequence repeat (ISSR)

Summary Orobanche species are commonly identified using morphological characteristics. In many cases, the distinction of closely related species is difficult, and a molecular tool is more suitable to differentiate them. In this study, genomic polymorphism between morphologically distinct species was investigated through amplification by polymerase chain reaction (PCR) of intersimple sequence repeat (ISSR) regions. Five primers were used to study genetic variation in the morphologically distinct species O. hederae and O. amethystea, as well as the closely related species O. cernua and O. cumana. For the first two species, all the primers detected genetic polymorphism. Anchored primers allowed the identification of more specific molecular markers than non‐anchored tri‐ and tetranucleotide primers. Genetic polymorphism was investigated among three O. hederae populations using the two types of primer. One non‐anchored and two anchored primers detected intraspecific variation, which was not correlated with the geographical location of those populations. The primer (GATA)₄ detected polymorphism between five specimens each of O. cernua and O. cumana species collected from different countries, permitting these two closely related species to be clearly differentiated. This study demonstrated that ISSR markers can be highly reliable for precise identification of Orobanche species.     

Phytophthora urerae sp. nov., a new clade 1c relative of the Irish famine pathogen Phytophthora infestans from South America

An unknown Phytophthora species was discovered in the central Peruvian Andes on blighted foliage of the native South American plant species Urera lacineata. Urera is a genus of native flowering shrubs in the nettle family Urticaceae. This new taxon Phytophthora urerae sp. nov. is herewith formally described based on extensive morphological analysis, phylogenetic analysis of nuclear and mitochondrial loci, and AFLP analysis. Phytophthora urerae sp. nov. is a close relative of the Irish famine pathogen, Phytophthora infestans, and only the third clade 1c taxon described from South America to date. In contrast to the clade 1c taxon Phytophthora andina, first described in South America as a hybrid, P. urerae does not appear to be a hybrid based on cloning and sequencing nuclear loci. Findings of new species in South America may provide novel insights into the origin and evolutionary history of clade 1c Phytophthora species.     

A new species of Malus in China,Malus shizongensis Liu sp. nov

Based on morphological, molecular biological, and molecular systematic studies, we describe here a new species of Malus from Yunnan, China. We compared the morphology of this new species, Malus shizongensis Liu sp. nov, with three Malus species, including M. hupehensis, M. baccata, and M. micromalus. Although the appearance of M. shizongensis was similar to these three species, it differed in height, branch color, branch hair, and flower color. To better identify the taxonomy of this new species, genome of M. shizongensis and that of seven Malus species, including M. prunifolia, M. sylvestris, M. sieversii, M. hupehensis, M. baccata, M. robusta, and M. micromalus were analyzed. A phylogenetic tree based on genome analysis indicated that M. shizongensis was close to M. hupehensis. Furthermore, M. shizongensis had its species-specific SNPs, and the number of species-specific SNPs was similar to that of three close species(M. hupehensis, M. baccata, and M. micromalus). Based on the above information, we named this new species as M. shizongensis Liu sp. nov.     

Identification of Rosellinia species as producers of cyclodepsipeptide PF1022 A and resurrection of the genus Dematophora as inferred from polythetic taxonomy

Rosellinia (Xylariaceae) is a large, cosmopolitan genus comprising over 130 species that have been defined based mainly on the morphology of their sexual morphs. The genus comprises both lignicolous and saprotrophic species that are frequently isolated as endophytes from healthy host plants, and important plant pathogens. In order to evaluate the utility of molecular phylogeny and secondary metabolite profiling to achieve a better basis for their classification, a set of strains was selected for a multi-locus phylogeny inferred from a combination of the sequences of the internal transcribed spacer region (ITS), the large subunit (LSU) of the nuclear rDNA, beta-tubulin (TUB2) and the second largest subunit of the RNA polymerase II (RPB2). Concurrently, various strains were surveyed for production of secondary metabolites. Metabolite profiling relied on methods with high performance liquid chromatography with diode array and mass spectrometric detection (HPLC-DAD/MS) as well as preparative isolation of the major components after re-fermentation followed by structure elucidation using nuclear magnetic resonance (NMR) spectroscopy and high resolution mass spectrometry (HR-MS). Two new and nine known isopimarane diterpenoids were identified during our mycochemical studies of two selected Dematophora strains and the metabolites were tested for biological activity. In addition, the nematicidal cyclodepsipeptide PF1022 A was purified and identified from a culture of Rosellinia corticium, which is the first time that this endophyte-derived drug precursor has been identified unambiguously from an ascospore-derived isolate of a Rosellinia species. While the results of this first HPLC profiling were largely inconclusive regarding the utility of secondary metabolites as genus-specific chemotaxonomic markers, the phylogeny clearly showed that species featuring a dematophora-like asexual morph were included in a well-defined clade, for which the genus Dematophora is resurrected. Dematophora now comprises all previously known important plant pathogens in the genus such as D. arcuata, D. bunodes, D. necatrix and D. pepo, while Rosellinia s. str. comprises those species that are known to have a geniculosporium-like or nodulisporium-like asexual morph, or where the asexual morph remains unknown. The extensive morphological studies of L.E. Petrini served as a basis to transfer several further species from Rosellinia to Dematophora, based on the morphology of their asexual morphs. However, most species of Rosellinia and allies still need to be recollected in fresh state, cultured, and studied for their morphology and their phylogenetic affinities before the infrageneric relationships can be clarified.     

温度对住宅区气体污染物扩散的影响

温度在气体污染物扩散的过程中起一定的作用。在现实生活中,由于日晒和地表辐射的存在,使得地面、建筑物外表面都与空气存在一定的温差。温差的存在会改变地表及壁面附近的流场,从而对住宅区污染物的扩散产生影响。利用理论推导对热力因素及扩散因素的关系进行了研究,并且与数值模拟的试验结果进行比较。结果发现理论推导与试验结果整体趋势相一致。这表明在与无温差情况相比较,温差存在时,地表及壁面附近流场更加紊乱;温差与气体污染物的扩散具有正相关性,对住宅区污染物的稀释起积极作用。     

森林对降水的影响概述

森林能否增加降水,这是植树造林、美化环境等工作中必然要考虑的问题。文章总结了国内外相关文献,就森林对降水的影响做了阐述。综合现有研究结果来看,森林对降水有无影响目前还没有普遍性的结论;对于局地森林对降水的影响应持保守态度,既不能说"有",也不能说"无"。明确的结论必须结合当地地形、天气、气候条件做具体的研究分析后才能得出,这样的结论才更科学,更具指导意义。因此关于宁夏植树造林是否对宁夏的区域气候产生影响,以及有什么样的影响,目前还不清楚。另外一个主要问题就是森林的尺度,即多大面积的森林才会对区域降水产生影响,因为如果森林的面积很有限,对区域降水的影响是否也很有限等等,这些问题都需要进一步深入研究和探讨。