滇西北地区冬虫夏草和阔孢虫草的遗传分化研究

应用随机扩增多态性DNA（RAPD）技术对来自云南西北部高黎贡山和丽江玉龙雪山的6个冬虫夏草Cordycepssinensis（Berk．）Sacc．,来自德钦地区三个地方的8个阔孢虫草C.crassisporaZang,YangetLi以及来自云南昆明的一个蛹虫草C.militaris（Vuill）Fr．进行分析。18个随机引物获得的RAPD谱带清晰并呈现多态。遗传距离分析表明,冬虫夏草／阔孢虫草与蛹虫草之间存在显著的遗传差异。冬虫夏草与阔孢虫草之间的遗传差异较为明显。在同种虫草个体中,来自同一地方的样本间遗传差异较小,不同地方的样本间遗传差异较大。说明云南虫草的不同地理群体间存在遗传分化。应用UPGMA和NJ法构建的分子系统树将来自不同地方的冬虫夏草及阔孢虫草分别聚在一起,提示RAPD标记在虫草群体中有显著的地区特异性。RAPD作为有效的遗传标记,可在分子水平上研究虫草属的遗传分化、起源和系统演化等。     

稻瘟病抗病基因Pi15的精细定位

稻瘟病抗病基因Pi15曾被作者鉴定为与已知抗病基因Pii具有连锁关系,但是,Pii基因究竟位于染色体6还是9上存在争议.为了确定Pi15基因的染色体位置,利用分子标记在由15个抗病个体和141个感病个体组成的F2群体中,通过混合群体分离法(BSA)与隐性群体分析法(RCA)相结合的手段,对目标基因进行了连锁分析.首先,从染色体6和9分别选择10个微卫星标记进行了分析,结果表明,只有位于染色体9的RM316与目标基因连锁,重组率为(19.1±3.7)%.为了进一步确定这种连锁关系,从染色体9选择了4个序列标定位点(STS)标记进行分析,结果表明,只有G103与目标基因连锁,重组率为(5.7±2.1)%.为了获得与目标基因更加紧密连锁的分子标记,对目标基因进行了RAPD)分析.在筛选、分析了1 000个随机引物之后,从中获得了3个目标基因紧密连锁的分子标记BAPi15486、BAPi15782、BAPi15844.它们与目标基因的重组率分别为0.35%、0.35%和1.1%.这些紧密连锁的分子标记可作为分子标记辅助基因聚合和克隆的出发点.     

稻瘟病菌效应蛋白的分泌特征及其在水稻细胞中的转运

许多病原菌能够通过分泌不同的效应蛋白以调控植物的防御以及胞内进程,从而助其有效入侵植物组织。稻瘟病菌的效应蛋白根据其不同的定位特点,被分为细胞质效应蛋白与质外体效应蛋白两类。在侵染过程中,细胞内的侵染菌丝被源于宿主植物的交界面菌丝膜(extrainvasive hyphal membrane, EIHM)包围,由EIHM与侵染菌丝细胞壁形成的质外体隔间是效应蛋白分泌的"必经通道"。此外,在稻瘟病菌侵染过程中会形成一个高度局部化的结构—活体营养表面复合体(biotrophic interfacial complex, BIC),它能够聚集由侵染菌丝分泌的细胞质效应蛋白。该文综述了稻瘟病菌效应蛋白的功能及其迁移过程,介绍了BIC的两个重要的形成阶段,阐明了不同效应蛋白的定位特点以及胞间转运的动态过程,揭示了效应蛋白分泌、转运至水稻细胞质以及在水稻细胞之间移动的分子机制。     

Effect of a Photo-synthetic Inhibitor on Tryptamine Pathway-mediated Sekiguchi Lesion Formation in Lesion Mimic Mutant of Rice Infected with Magnaporthe grisea

A lesion-mimic mutant of rice (cv. Sekiguchi-asahi) showed enhanced resistance to Magnaporthe grisea infection, thereby inducing Sekiguchi lesion ( sl ) formation and tryptamine accumulation under light. Both Sekiguchi lesion formation and tryptamine accumulation in leaves infected with M. grisea were inhibited by pretreatment with the photosynthetic inhibitor, 3-(3, 4-Dichlorophenyl)-1,1-dimethylurea (DCMU), which suppressed the gene expression of tryptophan decarboxylase ( TDC ), monoamine oxidase activity, H₂O₂ generation and DNA fragmentation. Catalase activity was inhibited by M. grisea infection under light, but magnitude of the inhibition was reduced in leaves pretreated with DCMU. Furthermore, tryptophan accumulated in M. grisea- infected leaves under light but not in DCMU-pretreated ones. Interestingly, such DCMU inhibition was reduced in the presence of tryptophan. Our studies suggest that chloroplasts function as the inhibitor of anti-oxidant system such as catalase activity and the supplier of a precursor of tryptamine and tryptophan in the sl mutant infected with M. grisea .     

A new species of Boletopsis Associated with Pinus sylvestris L. in Scotland

Summary

The identity of a recent Scottish collection thought to be Boletopsis leucomelaena was examined with the help of molecular techniques. This poroid fungus proved to be a new species of Boletopsis differing from the European species occurring with Pinus sylvestris, which should continue to be called B. grisea. The new name Boletopsis peplexa is introduced for all the Scottish collections with Pinus sylvestris.     

The effect of take-all disease on gas-exchange rates and biomass in two winter wheat lines with different drought response

There have been no studies of the effect of take-all on leaf gas-exchange rates, despite the fact that take-all severely restricts plant water and nutrient uptake, which results in significant biomass and grain yield reduction. Here we describe the effect of inoculation with Gaeumannomyces graminis (Sacc.) var. tritici (Ggt) on carbon assimilation rate (A) and biomass production of wheat plants grown under two water regimes. We show that the impact of Ggt inoculation on plant growth and leaf A may be through reduced photosynthetic capacity of the leaves and not water stress per se. The nature of this reduced photosynthetic capacity remains uncertain but may involve nutrient deficiency and different enzymes produced by the fungus. In each of the 3 years the experiment was conducted, Ggt significantly reduced A, i.e. at anthesis by 18% in 2000, 15% in 2001, and 12% in 2002. In agreement with other field studies, Ggt reduced tiller number and production of all plant components, mostly root dry mass and grain mass per plant. Highly significant negative correlations were found between disease rating and A in all years, showing that at disease ratings equal or higher than 3 (on a scale from 1 to 4) A could practically be zero. While A decreased, intercellular CO₂ concentration increased or did not change, and stomatal conductance was relatively high. In addition, A was more reduced under high than under low soil moisture content. These results support the idea that water stress per se did not contribute to the observed reduction of A. The mechanism of photosynthetic capacity reduction due to the Ggt root-rotting fungus is of interest as it may lead to the molecular mechanisms of plant resistance and ultimately to the development of take-all resistant plants.     

Sensitivity of Magnaporthe grisea to the Sterol Demethylation Inhibitor Fungicide Propiconazole

Baseline sensitivity of Magnaporthe grisea to a sterol demethylation inhibitor (DMI) propiconazole was determined using 52 wild-type single-spore isolates. The 50% effective concentrations of these 52 isolates to propiconazole ranged from 0.145 to 1.446  μ g/ml. Among the 52 isolates, two (07–82 and 04–006) were hypersensitive to propiconazole. The propiconazole-hypersensitive (PHS) isolates were also hypersensitive to another DMI fungicide triadimefon, but not to a benzimidazole fungicide carbendazim. Compared with the propiconazole-sensitive (PS) isolates, the PHS isolates retained normal pathogenicity. Real-time PCR analysis showed that expression of cyp51 gene in the PHS isolates was not significantly different from that in the PS isolates. Analysis of DNA sequence of cyp51 gene showed that the PHS isolates 07–82 and 04–006 had an amino acid substitution at the codon position 234 and 450, respectively, where the amino acids were conserved in the CYP51 of other fungi, which indicated that the substitutions in CYP51 might be related to hypersensitivity of M. grisea to DMI fungicides.