Evaluation of chickpea resistance against some isolates of Ascochyta rabiei, the causal agent of ascochyta blight

Ascochyta blight, incited by Ascochyta rabiei (Pass.) Lab., is one of the most important fungal diseases that has been shown to cause significant yield losses on chickpeas in Kermanshah province, Iran. One of the most effective and reliable methods of controlling the disease has been the use of resistant cultivars worldwide. This requires the identification of the physiological races of the fungus in the region in advance. In this regard, pathogenicity of 30 isolates of A. rabiei was determined using 10 differential chickpea varieties (mean of 1-9 degree of disease in three replications) under greenhouse conditions. In this respect, isolates fell into four groups, whereas based on infection type three groups were identified using cluster analysis. Disease resistance of four chickpea cultivars, Hashem, Jam, ILC-482 and Bivanij, were evaluated against isolates from each of three groups separately and in combination in the greenhouse and field conditions (with 4 replications). The experiment was repeated twice with three replications in greenhouse. Chickpea cultivars were sprayed with fungal spore suspension (2x10(5) spores/ml). Results showed that Jam and Bivanij cultivars were susceptible under greenhouse as well as field conditions. Hashem was tolerant to group I and susceptible to groups II and III and in the field. ILC-482 was tolerant to groups II and I and susceptible to group III and the combination of groups under greenhouse condition.     

Suppression of phenylalanine ammonia-lyase activity elicited in date palm by Fusarium oxysporum f. sp. albedinis hyphal wall elicitor

The inoculation of the seedling roots of the resistant (Bousthami Noir) and susceptible (Jihel) date palm (Phoenix dactylifera) cultivars by Fusarium oxysporum f. sp. albedinis induced an increase in phenylalanine ammonia-lyase (PAL) activity. The response of the PAL activity in the resistant cultivar was faster and higher than in the susceptible one. However, the elicitation of the seedlings with the hyphal wall elicitor (HWE) of the pathogen induced identical PAL activity in both cultivars. In the resistant cultivar, the the PAL activity elicited with the HWE was not influenced by the addition of the fungal culture filtrate (FCF) whereas it was suppressed in the susceptible cultivar. This FCF suppressor effect was dose-dependent, not influenced by sodium periodate, whereas it was strongly reduced by the heat (121 °C for 45 min) and pronase E. These results show that differential induction of the defence mechanisms in both cultivars was not related to differences in the induction of the PAL activity, but to the suppression of its elicitation in the susceptible cultivar.     

Host plant resistance of different chickpea genotypes against Ascochyta rabiei (Pass.) Lab. under tunnel conditions

Host plant resistance is the most efficient and easy way to manage chickpea blight caused by Ascochyta rabiei (Pass.) Lab. For this purpose, 374 chickpea lines/varieties from various research organisations were evaluated in plastic tunnels. None of the line showed immune response against the blight; however, one line (K-01005) was found to be highly resistant. Moreover, 15 entries were resistant, 136 exhibited moderate resistant reaction, 150 were susceptible and 72 showed highly susceptible response. The genotypes found that resistance against blight can serve as a source of resistance for breeding programmes, and they could be released for commercial production directly.     

Virulence diversity of Ascochyta rabiei the causal agent of Ascochyta blight of chickpea in the western provinces of Iran

Chickpea is the third most important food legume in the world. The most important limiting factor for the chickpea production in the world, including Iran, has been the Ascochyta blight. The pathogenic variation of 40 Ascochyta rabiei isolates from the western provinces of Iran was assessed on eight chickpea differential lines. The results revealed that A. rabiei population is diverse in the western provinces of Iran and the virulence rating of isolates across differential lines showed a large but continuous pathogenic variability. Based on the statistical analysis and the continuous response in differential lines, it was not possible to categorise A. rabiei isolates in the present study into pathotypes or races. Information obtained from the current study can be valuable in developing quarantine methods aimed to prevent dissemination of highly virulent isolates and in the development of durable resistant cultivars against the Ascochyta blight of chickpea.     

白车轴草病原菌链格孢菌及其症状研究

通过对不同白车轴草无性系病叶样本的病原菌分离、接种、鉴定及致病力测定,并结合野外观察,研究了安徽铜陵铜尾矿区白车轴草叶斑病病原菌链格孢菌(Alternaria tenuisNees)的致病、发病状况和寄主植物的抗病性、研究表明,不同白车轴草无性系抗病性有明显差异,根据寄主植物发病情况,以及病斑大小、形状、颜色等,将白车轴草无性系分为抗病型(R)和感病型(S)。     

Studies on the expression of marker genes in chickpea

Conditions were established for the optimum transient expression of beta-glucuronidase and neomycin phosphotransferase II genes introduced into zygotic embryos of chickpea (Cicer arietinum L. 6153 and CM72) by accelerated tungsten particles. Plasmid DNA at a concentration of 12 microgram per milligram of tungsten particles when accelerated with an inflow of helium gas at 60 kilogram per square centimeter through a distance of 24 centimeter in a chamber maintained at a negative pressure of 71.12 centimeter of mercury, resulted in optimal transient expression of the beta-glucuronidase gene in chickpea embryos. However, the expression of the marker genes was 20-40% higher under a cauliflower mosaic virus promoter in comparison to the Win6 and actin promoters. When Agrobacterium tumefaciens was used to transfer marker genes into zygotic embryos and the resultant plants were analysed for activity of the beta-glucuronidase and neomycin phosphotransferase II genes, both of these genes were expressed in tumorous tissues. When a disarmed strain of Agrobacterium was used, normal shoots were regenerated in which the lower parts showed expression of both genes at a frequency of 20%. This revised version was published online in June 2006 with corrections to the Cover Date.     

Mapping quantitative trait loci in chickpea associated with time to flowering and resistance to Didymella rabiei the causal agent of Ascochyta blight

Drought is the major constraint to chickpea (Cicer arietinum L.) productivity worldwide. Utilizing early-flowering genotypes and advancing sowing from spring to autumn have been suggested as strategies for drought avoidance. However, Ascochyta blight (causal agent: Didymella rabiei (Kov.) v. Arx.) is a major limitation for chickpea winter cultivation. Most efforts to introgress resistance to the pathogen into Kabuli germplasm resulted in relatively late flowering germplasm. With the aim to explore the feasibility of combining earliness and resistance, RILs derived from a cross between a Kabuli cultivar and a Desi accession were evaluated under field conditions and genotyped with SSR markers. Three quantitative trait loci (QTLs) with significant effects on resistance were identified: two linked loci located on LG4 in epistatic interaction and a third locus on LG8. Two QTLs were detected for time to flowering: one in LG1 and another on LG2. When resistance and time to flowering were analyzed together, the significance of the resistance estimates obtained for the LG8 locus increased and the locus effect on days to flowering, previously undetected, was significantly different from zero. The identification of a locus linked both to resistance and time to flowering may account for the correlation observed between these traits in this and other breeding attempts.     

橘全爪螨对双甲脒的抗性选育及其P450基因的表达差异分析

为了对双甲脒进行抗性风险评估, 弄清P450基因在橘全爪螨Panonychus citri抗药性中的作用, 在室内用双甲脒对橘全爪螨进行了抗性选育和交互抗性研究, 同时分析了橘全爪螨双甲脒抗性和敏感品系P450基因表达差异。经过12代抗性选育, 获得了橘全爪螨双甲脒抗性品系, 与敏感品系比较, 橘全爪螨对双甲脒的抗性倍数达到26.32倍。抗性风险评估表明, 橘全爪螨对双甲脒抗性遗传力h²为0.148。螺螨酯、 丁醚脲、 炔螨特和三唑锡对抗性品系的LC₅₀分别为敏感品系的16.85, 4.98, 2.13和2.05倍, 表明双甲脒抗性品系对螺螨酯、 丁醚脲、 炔螨特和三唑锡具有明显的交互抗性。阿维菌素、 苯丁锡、 哒螨灵、 矿物油对抗性品系LC₅₀分别为敏感品系的1.10, 1.21, 0.67和0.99倍, 表明双甲脒抗性品系对上述4种药剂没有显著的交互抗性。基因差异性分析发现, 抗性品系中有16条P450基因发生了上调, 27条P450基因发生了下调, 其中CYP389A6上调倍数最高［log₂ratio (RS/SS)=11.526］, CYP389A2下调倍数最高［log2ratio(RS/SS) =-12.683］, 由此推断, CYP389A6上调和CYP389A2下调可能是橘全爪螨对双甲脒产生抗性的重要原因。     

Involvement of ethylene signaling in Azospirillum sp. B510-induced disease resistance in rice

A bacterial endophyte Azospirillum sp. B510 induces systemic disease resistance in the host without accompanying defense-related gene expression. To elucidate molecular mechanism of this induced systemic resistance (ISR), involvement of ethylene (ET) was examined using OsEIN2-knockdown mutant rice. Rice blast inoculation assay and gene expression analysis indicated that ET signaling is required for endophyte-mediated ISR in rice.

Abbreviations: ACC: 1-aminocyclopropane-1-carboxylic acid; EIN2: ethylene-insensitive protein 2; ET: ethylene; ISR: induced systemic resistance; JA: jasmonic acid; RNAi: RNA interference; SA: salicylic acid; SAR: systemic acquired resistance     

Molecular analysis of Ascochyta rabiei (Pass.) Labr., the pathogen of ascochyta blight in chickpea

Genetic diversity in Ascochyta rabiei (Pass.) Labr., the causative agent of ascochyta blight of chickpea, was determined using 37 Indian, five American (USA), three Syrian, and two Pakistani isolates. A total of 48 polymorphic RAPD markers were scored for each isolate and the data used for cluster analysis. Most of the isolates clustered in the dendrogram essentially according to geographic origin. Based on the two major clusters A and B, Indian isolates were grouped into two categories, type-A and type-B. Isolates of A. rabiei within the Punjab state were more diverse than isolates from other states in northwestern India. A DNA marker (ubc756_{1.6 kb}), specific to Indian isolates was identified. This is the first report of a molecular diversity analysis of Indian isolates of A. rabiei. The information may assist Indian chickpea breeders in the proper deployment of blight-resistant cultivars and in disease management. Received: 25 April 2000 / Accepted: 11 July 2000     

Influence of bacterial leaf blight on the photosynthetic characteristics of resistant and susceptible rice

The effect of crop disease on photosynthetic characteristics is important for disease control. Two varieties, Shenzhou 98 and Neiwuyou 8015 with resistance and susceptibility to bacterial leaf blight (BLB), respectively, were selected, and the responses of the net photosynthetic rate (P_N) to active photon flux density (PPFD) and intercellular carbon dioxide concentration (C_i), as well as chlorophyll fluorescence, pigments and stomatal resistance (SR), were measured. The results showed that BLB infection greatly decreased the maximum photosynthetic rate (P_max), light saturation point (LSP), carboxylation efficiency (CE), maximal fluorescence (F_m) and actual photochemical efficiency of PSII ( Φ _PSII) but increased the light compensation point (LCP) and dark respiratory rate (R_D), which suggested that the performance of rice photosynthesis was decreased by BLB infection. The BLB infection had a lower effect on resistant rice Shenzhou 98 than on susceptible rice Neiwuyou 8015. The reduction of pigment and increased SR caused by BLB infection may have resulted in the decline in the photosynthetic rate. Significant effects of the BLB infection were observed on chlorophyll fluorescence F_m and Φ_PSII in resistant and susceptible rice. These parameters may be useful for noninvasive monitoring of plant disease considering the negative effect caused by other stresses.     

Effects of colonization of a bacterial endophyte,Azospirillum sp. B510, on disease resistance in tomato

A plant growth-promoting bacteria, Azospirillum sp. B510, isolated from rice, can enhance growth and yield and induce disease resistance against various types of diseases in rice. Because little is known about the interaction between other plant species and this strain, we have investigated the effect of its colonization on disease resistance in tomato plants. Treatment with this strain by soil-drenching method established endophytic colonization in root tissues in tomato plant. The endophytic colonization with this strain-induced disease resistance in tomato plant against bacterial leaf spot caused by Pseudomonas syringae pv. tomato and gray mold caused by Botrytis cinerea. In Azospirillum-treated plants, neither the accumulation of SA nor the expression of defense-related genes was observed. These indicate that endophytic colonization with Azospirillum sp. B510 is able to activate the innate immune system also in tomato, which does not seem to be systemic acquired resistance.     

Ascochyta blight of chickpea reduced 38% by application of Aureobasidium pullulans (anamorphic Dothioraceae,Dothideales) to post-harvest debris

In 2004–2005, application of non-amended suspensions of Aureobasidium pullulans conidia to post-harvest chickpea debris resulted in 37.9% fewer Ascochyta blight lesions on chickpea test plants relative to controls. Analogous tests in 2006–2007 resulted in 38.4% fewer lesions. Ascospores released from debris were predominantly Davidiella sp. (anamorph, Cladosporium sp.), followed by Didymella rabiei (anamorph, Ascochyta rabiei, agent of Ascochyta blight).     

肺炎克氏杆菌nifA基因在巴西固氮螺菌固氮基因表达的铵调节中的作用

固氯螺菌(Azospirillum)是一类仅在限铵和微好氧条件下固氮的微生物,它可与许多禾本科作物联合共生⑴,具有较大的应用潜力。铵作为固氮作用的调节信号,在固氮螺菌的实际应用中是首要的限制因素。在固氯螺菌中,铵不但具有与肺炎克氏杆菌(Klebsiella pneumoniae)相似的阻遏固氮酶合成的作用,而且还对已合成的固氮酶进行活性调节⑵。研究表明,其固氮酶翻译后活性调节的机制类似于深红红螺菌(Rhodospirillum rubrum)⑶,即在有铵条件下其固氮酶铁蛋白的一个亚基被共价修饰而丧失活性,这一过程是可逆的。由于铵在固氮螺菌中双水平地调节固氮作用,使得在野生菌株中研究其固氮基因表达水平上的调节较为困难。Zhang等⑷利用区域定位诱变技术获得了巴西固氮螺菌Sp7（A．Brasilense Sp7)的draT-突变株,在该突变株中铵不再影响固氮酶的活性,这为其固氮基因表达调节的研究提供了一个良好的材料。本文将组成型表达的肺炎克氏杆菌nifA基围引入该突变株中,通过分析讨论铵对巴西固氮螺菌固氮基固表达的调节作用方式。     

Time-course analysis of the phenols in cucumber mosaic virus-resistant, -tolerant and -susceptible tomato genotypes

In this study, changes in quantity and quality of phenolic compounds were compared in cucumber mosaic virus (CMV)-inoculated and -un-inoculated plants of nine resistant, tolerant, susceptible and highly susceptible genotypes at three different time intervals. Total phenolic contents and the number of phenolic compounds were generally increased in CMV-inoculated plants. Maximum per cent increase in total phenolic contents over un-inoculated controls was observed as 77.55% in resistant genotype TMS-1, 84.17% in tolerant genotype L06238 and 82.88% in resistant genotype L02223 after 10, 20 and 30 days of inoculation, respectively. Thin layer chromatography of inoculated and un-inoculated plants indicates that in most of the tested genotypes, the number of phenolic compounds varied from cultivar to cultivar and within the same cultivar, depending upon the status of plants and growth stages. However, the trend of increase in quantity and quality of phenolic compounds in the tested units was not constant to draw a meaningful conclusion.     

水稻白叶枯病抗性基因Xa21和稻瘟病抗性基因Pi-d2激酶蛋白质在毕赤酵母中的表达及条件优化

【目的】白叶枯病和稻瘟病是最主要的水稻病害,Xa21是水稻白叶枯病抗性基因,Pi-d2是稻瘟病抗性基因,二者都编码类受体激酶蛋白质。本研究旨在毕赤酵母系统中表达XA21和PI-D2激酶蛋白质。【方法】用Xa21和Pi-d2的激酶区PCR产物,构建了pPICZαA-Xa21K、pPICZαA-Pi-d2K重组质粒,酶切及测序验证后,将重组质粒线性化,转化到毕赤酵母菌株中,系统地比较了不同酵母菌株(KM71、GS115、X33),不同甲醇浓度(1%、2%、3%),不同pH(pH5、pH6、pH7、pH8)值,不同诱导时间(24h、48h、72h)条件下激酶蛋白质的表达情况。【结果】XA21和PI-D2激酶蛋白质可以在毕赤酵母中表达,但表达的蛋白质不能分泌到培养基上清中,而只能在菌体中检测到,对表达条件的系统比较发现,毕赤酵母菌株KM71和X33、2%的甲醇诱导浓度、pH5和48h以上的诱导时间有利于激酶蛋白质的表达,最后我们在酵母裂解物上清中获得了纯化的考染可见的激酶蛋白质。【结论】在毕赤酵母中表达了XA21和PI-D2激酶蛋白质,为下一步生化特性研究奠定了基础。     

Biochemical alterations in leaves of resistant and susceptible cotton genotypes infected systemically by cotton leaf curl Burewala virus

Leaf curl disease caused by Cotton Leaf Curl Burewala virus (CLCuBuV) has been recognized as serious threat to cotton in Indian subcontinent. However, information about cotton–CLCuBuV interaction is still limited. In this study, the level of phenolic compounds, total soluble proteins, and malondialdehyde (MDA) and the activities of phenylalanine ammonia-lyase (PAL), peroxidase (POX), catalase (CAT), proteases, superoxide dismutase (SOD), and polyphenol oxidase (PPO) were studied in leaves of two susceptible (CIM-496 & NIAB-111) and two resistant (Ravi and Co Tiep Khac) cotton genotypes. Disease symptoms were mild in the resistant genotypes but were severe in highly susceptible genotypes. The results showed that phenolic compounds, proteins, PAL, POX, CAT, proteases, SOD, PPO, and MDA play an active role in disease resistance against CLCuBuV. The amount of total phenols, proteases, MDA, and PPO was significantly higher in leaves of CLCuBuV-inoculated plants of both resistant genotypes as in non-inoculated plants, and decreased in CLCuBuV-inoculated plants of both susceptible genotypes over their healthy plants. POX, protein content, SOD, and PAL activities showed lower values in resistant genotypes, while they decreased significantly in susceptible genotypes as compared to the noninoculated plants except PAL, which showed non-significant decrease. CAT was found to be increased in both susceptible and resistant genotypes with maximum percent increase in resistant genotype Ravi, as compared to non-inoculated plants. The results showed significantly higher concentrations of total phenols and higher activity of protease, MDA, SOD, and PPO in resistant genotype Ravi after infection with CLCuBuV, suggesting that there is a correlation between constitutive induced levels of these enzymes and plant resistance that could be considered as biochemical markers for studying plant-virus compatible and incompatible interactions.     

吉林人群强直性脊柱炎6号染色体短臂上的HLA区域遗传易感基因定位研究

为了寻找中国人群中与强直性脊柱炎相关的新的易感基因及其所在位置, 在与强直性脊柱炎强连锁的6 号染色体短臂上的HLA基因区域内选取11个SNPs多态位点, 通过对中国吉林地区79名AS患者和132名正常对照者进行case-control分析, 发现TNF-a -850处TT突变基因型在AS组中的分布高于正常对照组（P=0.027）, 突变型T等位基因在AS组和正常对照组中的分布差异更为显著（P=0.002）。通过多位点之间的连锁不平衡分析发现, LTA基因、TNF-a基因、LST1基因和NCR3基因中的 5个SNPs多态位点之间存在连锁不平衡, 范围是15 kb, 在这5个SNPs多态位点组成的单体型中, TCTTC单体型在AS组和正常对照组中的分布有显著差异（c2=7.406, P=0.0065）,并且该单体型中含有具有统计学意义的TNF-a –850的突变型等位基因T。提示在LTA、TNF-a、NCR3和LST1 这4个基因构成的15 kb范围内可能存在增加AS患病易感性的位点, 可能是TNF-a –850 C→T突变, 也可能是在TNF-a –850附近的其他位点。     

基于多目标评价方法的乳腺癌易感基因排序及其网络表达研究

目的利用已有的研究结果和数据,采用多目标评价方法建立乳腺癌易感基因评价模型,对与已知乳腺癌基因关系密切的其它基因进行分析和排序,并给出结果的网络表达模式。方法通过分析已有的文献,并利用有关的基因数据库和已有文献中的数据,提炼出乳腺癌易感基因的多目标评价体系,构建基于加权和法的乳腺癌易感基因评价模型,并利用Cytoscape软件进行评价结果计算和评价结果的网络模式表达。结果利用多目标模型所得到的评价结果,与已有的研究结果一致。其中,乳腺癌易感基因TopBP1排名第二,已知乳腺癌候选易感基因HMMR排名第六。结论文章提出的多目标评价模型能够准确评价被选基因与乳腺癌易感性之间的关系,所提出的评价方法与相关软件结合使用,将成为癌症易感基因研究方面有效的分析方法和途径。