红掌细菌性疫病的病原菌初步鉴定

 在云南西双版纳的红掌上发现一种由细菌侵染引起的病害,从叶片的病组织上分离到具有致病性的杆状细菌,将分离的病原菌接种于健康的红掌上,表现出与田间一致的症状。感病初期在叶缘或叶脉间出现水渍状小点,后期病斑多呈棕褐色至黑色坏死,病健交界处多呈黄色。从接种发病的病斑与田间标样上分离的病原菌菌落形态完全相同。通过菌株的培养性状、常规生理生化特性及透射电镜下菌体形态观察结果,将病原菌初步鉴定为黄单胞菌属(Xanthomonas)。BIOLOG鉴定和致病性测定结果进一步鉴定病原菌为地毯草黄单胞菌花叶万年青致病变种Xanthomonas axonopodis pv. dieffenbachiae(Xad)(McCulloch & Pirone) Vauterin et al.     

INTERACTIVE EFFECT OF SULFUR AND NITROGEN ON GROWTH AND YIELD ATTRIBUTES OF OILSEED CROPS (BRASSICA CAMPESTRIS L. AND ERUCA SATIVA MILL.) DIFFERING IN YIELD POTENTIAL

Field experiments were conducted to determine the interactive effect of sulfur (S) and nitrogen (N) on growth and yield attributes of oilseed crops [Brassica campestris L. (V₁) and Eruca sativa Mill. (V₂)] differing in yield potential. Two combinations of S and N (in kg ha^?1): 0S + 100N (?S+N;T₁) and 40S + 100N (+S+N;T₂) were used. Biomass accumulation, leaf area index (LAI), leaf area duration (LAD), and photosynthetic rate in the leaves were determined at various phenological stages. The results showed that the combined application of S and N (+S+N) significantly (P<0.05) improved the growth and yield attributes of both the genotypes compared with N applied alone (?S+N). Genetic variability was observed between the two genotypes in response to combined application of S and N (T₂). Genotype V₁ had higher biomass accumulation, photosynthetic rate, seed yield, oil yield, biological yield, and harvest index when compared with genotype V₂. Treatment T₂ resulted in 142, 95, 56, and 349% enhancement in biomass accumulation, leaf-area index (LAI), leaf-area duration (LAD) and photosynthetic rate, respectively in comparison with treatment T₁ in genotype V₁. Seed yield, oil yield, biological yield, and harvest index were improved by 141, 171, 85, and 30%, respectively, by treatment T₂ in comparison with T₁. In the case of genotype V₂, increase in biomass accumulation, LAI, LAD, and photosynthetic rate due to application of treatment T₂ were 156, 137, 125 and 467%, respectively, over the results of T₁. Seed yield, oil yield, biological yield and harvest index improved by 193, 251, 98, and 48%, respectively, with this treatment. On the basis of results obtained in this study, it can be concluded that sulfur must be included in the nutrient management package for optimum growth and yield attributes of oilseed crops. Furthermore, the yield potential of oilseed crops with low seed and oil yield can be improved using this treatment as achieved in our study in case of taramira (Eruca sativa Mill.), a genotype with low seed and oil yield.     

国外新引进水稻品种（系）对我国水稻白叶枯病致病型的抗性反应

采用成株期人工剪叶接种鉴定方法,评价451份新引进的国外水稻新品种（系）对我国田间流行的5个水稻白叶枯病致病型的抗性反应。结果显示国际水稻研究所新材料是水稻白叶枯病重要的抗源。本试验还筛选出一批抗性较好的抗性材料,可供育种家在选配亲本时选用。     

菜豆普通细菌性疫病菌在土壤和植株残体中的越冬能力

为评估菜豆普通细菌性疫病菌地毯草黄单胞杆菌菜豆致病变种或褐色黄单胞菌褐色亚种在土壤及植物残体中的越冬能力,对采自黑龙江、内蒙古、山西、河北及新疆的18块菜豆生产田的20份土壤及14份植物残体样品进行病原菌分离和鉴定。在MT选择性培养基上有12个土壤样品和13个植株残体样品提取液产生典型的类似黄单胞菌菌落。选取29个分离物进行致病性测定,有27个分离物对菜豆品种"英国红"致病。利用地毯草黄单胞杆菌菜豆致病变种和褐色黄单胞菌褐色亚种的特异性引物X4c/X4e及褐色黄单胞菌褐色亚种特异性引物Xf1/Xf2对29个分离物进行多重PCR检测,其中17个分离物为地毯草黄单胞杆菌菜豆致病变种,10个分离物为褐色黄单胞菌褐色亚种。结果表明,菜豆普通细菌性疫病菌可以在黑龙江、内蒙古、山西、河北的一些菜豆种植区的土壤及植株残体中越冬存活。     

水稻黄单胞菌致病相关基因插入突变体系的建立

 水稻白叶枯病菌（Xanthomonas oryzae pv. oryzae, Xoo）和条斑病菌（Xanthomonas oryzae pv. oryzicola, Xoc）是水稻上的模式病原菌,分别引起水稻白叶枯病（bacterial blight, BB）和细菌性条斑病（bacterial leaf streak, BLS）。为了精确和高效地实现目的基因的突变,本研究利用pK18mobGⅡ载体,建立了一套适于Xoo和Xoc目的基因定点插入的突变体系。通过同源片段与目的基因间的同源重组,成功获得了Xoo和Xoc的hrcV和hrpF突变体。PCR和Southern杂交证实：pK18mobGⅡ携带不同大小的同源片段,能够整合于hrcV和hrpF的特定位点;200～400 bp的同源片段能够获得最佳的突变效率;两亲接合的转化效率是电转化的5～100倍。毒性测定结果显示,hrcV基因决定着Xoo在水稻上的致病性。致病相关基因插入突变体系的建立为研究水稻黄单胞菌与水稻互作中致病相关基因的功能奠定了遗传学研究基础。     

Genomic variability and plasticity of Pseudomonas causing coffee leaf spots in Minas Gerais state,Brazil

Foliar spots caused by Pseudomonas coronafaciens pv. garcae (Pcg), Pseudomonas amygdali pv. tabaci (Pat) and Pseudomonas cichorii (Pch) are major bacterial diseases that can reduce coffee production. However, little is known about the genetic diversity and molecular mechanisms underlying the pathogenicity to coffee plants of these bacteria. In this study, genome sequences of Pcg, Pat and Pch strains isolated from coffee plants in Minas Gerais state, Brazil, were used to assess their variability and plasticity, and compare their type III secretion system (T3SS) and apoplastic effector repertoires as well as tabtoxin biosynthetic/detoxification genes. Genomic diversity was found for all three phytopathogens, among which Pch possesses the highest number of exclusive proteins. The Pcg genome is the most stable whereas that of Pch is the most plastic, which is related to their host ranges. When compared with those of Pseudomonas syringae pv. tomato DC3000, hrp/hrc gene sequences are more conserved in Pcg and Pat than in Pch, which also possesses the smallest T3SS and the largest apoplastic effector repertoires. The only T3SS effector family common to all three pathogens is AvrE, suggesting that, as for other plant–Pseudomonas interactions, it may play a crucial role for pathogenicity towards coffee plants. Apoplastic proteins associated with maintaining the redox balance and degrading proteins/peptides not previously described as important in plant–bacteria interactions were found. Gain/loss of the tabtoxin biosynthetic cluster with retention of the antitoxin gene was observed, indicating that tabtoxin production is not a limiting factor for the occurrence of mixed infections.     

水稻细菌性条斑病及其抗性研究进展

本文简要综述了近年来国内外对水稻抗细菌性条斑病在病原菌鉴定、水稻抗源筛选、抗性生理遗传以及抗性的分子生物学等方面的研究进展，以期为水稻细条病的深入研究提供参考。     

Production and preliminary characterization of monoclonal antibodies raised against <Emphasis Type="Italic">Xanthomonas campestris</Emphasis> pv. <Emphasis Type="Italic">mangiferaeindicae</Emphasis>

Bacterial black spot disease of mango is caused by Xanthomonas campestris pv. mangiferaeindicae (Xcm), which consists of two genotypically and phenotypically distinct groups of strains. Monoclonal antibodies (MABs) were produced – 15 against CFBP 1717, a group I strain, and 9 against CFBP 2919 (yellow-pigmented), a group II strain – and were analyzed for their characteristics. On the avidin-biotin peroxidase complex enzyme-linked immunosorbent assay, the dilution limit of the MABs was between 100 and 200000 and was 10 times higher when measured on the corresponding ascitic fluid. All kinds of isotypes were represented among the MABs. All the Japanese Xcm strains, designated group I by hrp-restriction fragment length polymorphism (RFLP) analysis, reacted equally with MAB 1A7H12G3, which is the most specific for all but one worldwide group I strains, and to only one strain among group II. Also, to various extents, serological heterogeneity inside the two groups was consistently differentiated based on isozyme and RFLP analyses. MAB 1E2E1 against CFBP2919, because of its narrow specificity, and MAB 1A7H12G3 against CFBP1717, because of its broad specificity, will be useful for epidemiological studies or general control of the pathogen.     

采用两种突变方法对甘蓝黑腐病菌XC_1348基因的功能解析

为研究甘蓝黑腐病菌Xcc8004基因组中一个功能未知的假定蛋白XC_1348的基因功能,本研究用自杀质粒pK18mob和pK18mobSacB分别通过同源单交换和同源双交换构建XC_1348的非极性整合突变体1348nk和有标记的缺失突变体DM1348Gm,并对两种突变体的表型进行检测,结果显示该基因突变后不影响细菌的胞外多糖（EPS）产量、胞外酶活性以及细菌游动性.有趣的是该基因的两种突变体的致病力存在较大差异,原因可能是Xcc经两种方法定点突变后分别具有的不同基因组结构而影响到某些基因的表达所致.通过研究初步了解了XC_1348基因的功能并为今后改进定点突变方法提供现实依据.     

过氧化脲及尿素配比对水培上海青生长及品质的影响

水培蔬菜中硝酸盐富集及供氧状况是当前水培体系亟待解决的问题.为降低水培上海青Brassica campestris ssp.Chinensis(L.)硝酸盐含量,本研究分别通过部分尿素替代日本园试配方中硝酸盐,以及不同过氧化脲(UHP)与尿素配比的方式,探究减硝增氧对水培叶菜生长及品质的影响.首先以30％、40％、50...