Components of resistance to late blight (Phytophthora infestans) in eight South AmericanSolanum species

Four components of partial resistance toPhytophthora infestans were measured after inoculation in the greenhouse and in the field ofSolanum arnezii x hondelmannii, S. berthaultii, S. circaeifolium, S. leptophyes, S. microdontum, S. sparsipilum, S. sucrense andS. vernei, and four hybrid progenies ofS. microdontum withS. tuberosum. The four components were infection efficiency, lesion growth rate, generation time and sporulation capacity. The results were compared with resistance ratings derived from field experiments, and with observations made on the potato cultivars Bintje, Bildstar, Libertas and Pimpernel. Genetic variation for all components was found, while the relative importance of the components of partial resistance appeared to vary between the species. InS. microdontum, generation time, infection efficiency and lesion growth rate, and inS. tuberosum infection efficiency, lesion growth rate and sporulation capacity appeared positively associated, but in other species no such association was found. A strong hypersensitive reaction, the expression of which appeared to depend on environmental conditions, was found inS. microdontum. ForS. berthaultii, infection efficiency appeared to be the main resistance component.Abbreviations ADPC area under the disease progress curve - IE infection efficiency - LGR lesion growth rate - GT generation time - SC sporulation capacity     

The effect of the presence of R-genes for resistance to late blight (Phytophthora infestans) of potato (Solanum tuberosum) on the underlying level of field resistance

The differential genotypes R₁, R₁₀ and R₁₁, as originally defined by Black, were crossed with R-gene-free cultivars and the progenies divided into two subpopulations comprising those which had inherited the R-gene and those which had not. The underlying level of field resistance of the two groups was compared in a field trial in which they were inoculated with an isolate that could overcome the relevant R-genes. The R-gene-bearing group was significantly ( P  < 0·001) more resistant than the R-gene-free group, with mean scores over four dates in 2000 of 4·86 and 4·09, respectively, on a 1–9 scale of increasing resistance, and of 4·10 and 2·35 on one date in 2001. However, the magnitude of the effect depended on the R-gene and the year of the trial. Data from a progeny of cv. Stirling (with an R-gene and a high level of field resistance) were examined and the same effect of an R-gene found. Fewer of the R-gene-bearing group of clones were highly susceptible, and more were resistant. The most resistant clones always bore the R-gene. It is concluded that increased resistance is conferred by the defeated R-gene or linked genes for field resistance.     

Selection and use of a mathematical model to evaluate components of resistance to Phytophthora infestans in potato

Five models of general epidemics, spatially homogeneous, were all shown to fit well to disease progress data forPhytophthora infestans on a susceptible potato cultivar. The models were: the logistic equation, the paralogistic or Vanderplank equation, two models from medical epidemiology with similar complexity, and a slightly more complex model with explicit treatment of lesion expansion. The use of the models for analysing the sensitivity of disease progress to changes in resistance components is discussed. Sensitivity analysis of the most complex model, by varying components within their range of genetic variation, indicates lesion expansion and infection efficiency as the components offering the best perspectives for resistance breeding. Improving two components simultaneously reduces disease progress slightly more than additively, but not enough to add other components to the list of breeding objectives. Pitfalls in using models for component sensitivity analysis, in the form of erroneous model initializations, are discussed, including implications for the role of components in the development of natural epidemics and in resistance breeding trials.     

大豆DNA脱甲基化酶相关基因的克隆及连作胁迫应答

利用大豆基因组数据库Phytozome v12.1.6获得大豆DNA脱甲基化相关基因Glyma03g34860和Glyma10g07601的CDS序列,以大豆叶片RNA为模板,RT-PCR克隆获得Glyma03g34860基因大小为5 226 bp,Glyma10g07601基因大小为6 045 bp。利用STRING在线软件预测这两个转录本的互作蛋白质完全一致,主要互作蛋白8个,包括一个AP位点裂解酶和2个RNA聚合酶亚基;采用qRT-PCR分析他们对大豆连作综合逆境胁迫的响应。结果表明:连作综合逆境胁迫使Glyma03g34860和Glyma10g07601的表达均不同程度上调,其中,Glyma10g07601基因在大豆品种安达农家、黑大豆、绥农14和黑农40达显著水平(P0.05),分别增加1.37、1.22、1.98倍和1.67倍;Glyma03g34860基因在大豆品种垦丰16、绥农14达显著水平(P0.05),分别增加1.62倍和1.65倍,因此推测他们可能通过使基因组DNA脱甲基化而参与大豆连作综合逆境胁迫的响应。     

Oxidative stress induces high transcription of Rhm52 and Rhm54, novel genes identified as being involved in recombinational repair in Magnaporthe grisea

The first two recombinational repair genes of Magnaporthe grisea were cloned. Analysis of the deduced amino acid sequences revealed that Rhm52 and Rhm54 are Saccharomyces cerevisiae RAD52 and RAD54 homologs, respectively. Phenotypic complementation testing of these genes showed their function in recombinational repair. Both genes were in single copies in M. grisea genome. Expression of these genes was induced by methyl methanesulfonate and ultraviolet radiation as known for other homologs of the RAD52 epistasis group. Higher induction of both genes by oxidative stress and heat shock indicated the probability for recombinational repair during the infection cycle of M. grisea. The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under the accession numbers AB091332 and AB091330     

Distribution of major clonal lineages EU_13_A2, EU_2_A1, and EU_23_A1 of Phytophthora infestans associated with potato late blight across crop seasons and regions in Algeria

Potato is one of the most important agricultural crops in Algeria and worldwide. Each year, potato late blight, caused by Phytophthora infestans, is responsible for significant damage that leads to large production losses, and is thus a direct threat to food security in Algeria. In this study, 131 isolates of P. infestans and 92 DNA fingerprints captured on FTA cards were sampled from commercial and seed production fields in three major potato production regions (western, eastern, and central) during the main-season and late-season in Algeria over six cropping seasons (2010–2016). Genotypes of P. infestans and population genetic diversity were analysed using a 17-plex simple-sequence repeat (SSR) marker assay, and the mating type of all isolates was characterized. Both mating types (A1 and A2) were found, and often occurred in the same field. Differences in mating type proportion were observed between regions and between sampling periods. Analysis with SSR markers showed the prevalence of the EU_13_A2 lineage (70%) over EU_2_A1 (16%), EU_23_A1 (10%), and 4% of unknown multilocus lineage (MLL). The EU_13_A2 showed differentiation within the group. EU_23_A1 was found mainly in late-season crops. However, the cropping region did not influence the distribution of lineages due to the dispersal of the pathogen in Algeria by seeds. Genetic structure did not reveal a clear variation in distribution of the three lineages throughout the sampling regions. These data provide important new information on the composition and change over time of P. infestans populations in Algeria and open the way for a better understanding of the local epidemiology of this important pathogen.     

四倍体马铃薯SSR遗传图谱的构建及晚疫病抗性QTL初步定位

利用四倍体马铃薯栽培种‘大西洋'和‘陇薯6号'杂交得到的190个F_1株系为作图群体,构建了四倍体马铃薯的分子遗传图谱,采用区间作图法对马铃薯晚疫病抗性进行了QTL初步定位。结果显示:通过对190个F_1株系进行检测,共发现有7个与晚疫病抗性相关的QTL位点,分别分布在第5、6、7、10和11连锁群上;各位点的LOD值在2.70~10.32之间,其中主效QTL位点3个(LOD≥3.5),可解释17.37%~65.68%的表型变异。获得紧密连锁的特异标记(S183-210、S148-460)为进一步进行QTL精确定位提供了参考。     

辣椒PP2C家族基因鉴定与响应低温胁迫的表达分析

对辣椒PP2C基因家族成员进行全基因组鉴定和特征分析,并研究CaPP2Cs基因在低温胁迫下的表达模式,结果表明：在辣椒参考基因组共系统鉴定出99个CaPP2Cs基因家族成员,并不均匀地分布在12条染色体上,CaPP2Cs基因编码的氨基酸数介于99~1 572 aa,分子量介于10.94~178.40 Da,等电点介于4.08~9.51。系统进化树分析可将辣椒和拟南芥的PP2C基因分为13个亚族,每个亚族均含有辣椒PP2C基因,基因结构分析表明CaPP2Cs基因的外显子数量介于1~18;在CaPP2Cs基因的启动子中发现许多与光、低温和激素响应有关的顺式作用元件。转录组数据分析表明,CaPP2C31基因在叶片中的表达量显著高于其他基因,CaPP2C16则特异性地表达于授粉后50 d的胎座中。低温处理24 h时,CaPP2C97和CaPP2C3在叶片中呈现显著的下调表达;低温处理1 h时,CaPP2C36、CaPP2C5、CaPP2C53、CaPP2C43、CaPP2C99等基因在根中明显上调,CaPP2C19、CaPP2C23、CaPP2C44、CaPP2C95则显著下调,表明CaPP2Cs可能在辣椒响应低温胁迫中发挥作用。     

Involvement of a vascular hypersensitive response in quantitative resistance to Ralstonia solanacearum on tomato rootstock cultivar LS‐89

Ralstonia solanacearum causes bacterial wilt disease in Solanaceae spp. Expression of the Phytophthora inhibitor protease 1 (PIP1) gene, which encodes a papain‐like extracellular cysteine protease, is induced in R. solanacearum‐inoculated stem tissues of quantitatively resistant tomato cultivar LS‐89, but not in susceptible cultivar Ponderosa. Phytophthora inhibitor protease 1 is closely related to Rcr3, which is required for the Cf‐2‐mediated hypersensitive response (HR) to the leaf mould fungus Cladosporium fulvum and manifestation of HR cell death. However, up‐regulation of PIP1 in R. solanacearum‐inoculated LS‐89 stems was not accompanied by visible HR cell death. Nevertheless, upon electron microscopic examination of inoculated stem tissues of resistant cultivar LS‐89, several aggregated materials associated with HR cell death were observed in xylem parenchyma and pith cells surrounding xylem vessels. In addition, the accumulation of electron‐dense substances was observed within the xylem vessel lumen of inoculated stems. Moreover, when the leaves of LS‐89 or Ponderosa were infiltrated with 10⁶ cells mL^?1 R. solanacearum, cell death appeared in LS‐89 at 18 and 24 h after infiltration. The proliferation of bacteria in the infiltrated leaf tissues of LS‐89 was suppressed to approximately 10–30% of that in Ponderosa, and expression of the defence‐related gene PR‐2 and HR marker gene hsr203J was induced in the infiltrated tissues. These results indicated that the response of LS‐89 is a true HR, and induction of vascular HR in xylem parenchyma and pith cells surrounding xylem vessels seems to be associated with quantitative resistance of LS‐89 to R. solanacearum.     

莲草直胸跳甲热激蛋白90基因的分子特征、表达模式及对温度胁迫的响应

莲草直胸跳甲Agasicles hygrophila是世界性入侵杂草空心莲子草Alternanthera philoxeroides的专食性天敌,冬季低温和夏季高温会影响其种群数量从而降低防控效果。为进一步探讨莲草直胸跳甲对温度胁迫适应性的分子生态机制,本研究对其热激蛋白90(AhHSP90)进行了蛋白结构、磷酸化修饰及系统发育等生物信息学分析,并采用荧光定量PCR检测了AhHSP90基因的时空表达动态及不同温度胁迫后的表达。RT-qPCR结果显示,AhHSP90在莲草直胸跳甲整个生活史及雌成虫各组织中均有表达;高温(30、35和40℃)、低温(-5、0、5、10、15和20℃)胁迫2 h后,AhHSP90在高温40℃下表达显著升高,但在其他温度下无显著差异。根据对AhHSP90分子特征、表达模式以及对温度胁迫的响应等方面的综合分析,推测其可能在莲草直胸跳甲发育及抵抗高温过程中发挥着重要的作用。     

Expression of genes related to Parkinson’s disease after paraquat treatment in Drosophila melanogaster

This study was designed to determine the minimum effective concentration of paraquat that modulated the expression of PKD-related genes in Drosophila. We first studied the viability of Drosophila and then tested the expression of the PKD-related genes—Parkin, UCH, and tau—in various concentrations of paraquat in the water sucked by Drosophila. The lowest effective concentration of paraquat was approximately 20 μM and the gene expression was induced at paraquat doses between 20 mM and 20 μM. Parkin and tau expression was inhibited, while that of UCH was significantly increased.Next, we examined the expression of the Parkin and UCH genes in the neurons of SOD-reduced mutants under oxidative stress conditions and found that Parkin was up regulated, while UCH was down regulated. We also found that the expression of Parkin was regulated by JNK. This study revealed that paraquat affects the expression of PKD-related genes via oxidative stress.In conclusion, our results showed that paraquat in the water sucked by Drosophila altered the gene expression at a minimum concentration of 20 μM, and that it not only promoted but also inhibited PKD-related gene expression via signal transduction mediated by oxidative stress. In order to confirm whether paraquat is a causal factor of PKD, more balanced and in-depth tests seem to be done looking into multiple aspects.     

棉铃虫表皮蛋白基因CP22和CP14的表达特征及其对甲氧虫酰肼的响应

为揭示棉铃虫Helicoverpa armigera表皮蛋白（cuticular protein,CP）基因在其生长发育及应对药剂胁迫中的作用,克隆棉铃虫2个CP基因CP22和CP14,利用实时荧光定量PCR技术分析其在不同发育阶段和不同组织中的相对表达量,并于显微镜下观察甲氧虫酰肼亚致死剂量处理后棉铃虫3龄幼虫的表皮形态,并用实时荧光定量PCR技术测定药后CP22和CP14基因的相对表达量。结果显示,CP22和CP14的开放阅读框全长分别为570 bp和393 bp,分别编码189个和130个氨基酸;CP22和CP14都具有1个几丁质结合域,属于CPR家族RR-1亚类;CP22和CP14基因均在棉铃虫5龄幼虫表皮中表达水平高;这2个基因在棉铃虫幼虫期的表达水平高于在卵期、蛹期和成虫期的表达水平,且在4龄幼虫体内表达量最高,在蜕皮后随着日龄的增加表达量逐渐降低;甲氧虫酰肼处理后棉铃虫3龄幼虫表皮黑化、皱缩,发生蜕皮异常,显微观察显示其内外表皮分离,真皮细胞解体;甲氧虫酰肼处理后24 h和48 h,棉铃虫CP22和CP14基因的相对表达量显著上调。表明棉铃虫CP22和CP14基因参与棉铃虫幼虫蜕皮,并且响应甲氧虫酰肼胁迫,可作为防治棉铃虫的潜在靶标基因。     

Association of MACE-based insecticide resistance in Myzus persicae with reproductive rate, response to alarm pheromone and vulnerability to attack by Aphidius colemani

Reproductive success and response to alarm pheromone, both potentially important components of fitness, were assessed using clones of Myzus persicae (Sulzer) to establish associations with insecticide resistance conferred by insensitive modified acetylcholinesterase (MACE). Both traits showed significant trends that were apparently related to this mechanism. MACE forms appeared to reproduce at slower rates than non-MACE forms expressing moderate (R1) levels of another resistance mechanism based on elevated carboxylesterase. However, MACE forms were more responsive to alarm pheromone than their non-MACE counterparts. The potential implications for parasitoid performance were tested using two clones showing clear differences in alarm response. The level of parasitism of M persicae by the parasitoid Aphidius colemani (Viereck) was significantly lower in MACE forms on pepper crops compared to non-MACE forms. In addition, the distribution of MACE and non-MACE forms differed on the pepper plants, with more MACE forms being found on the growing points. The presence of the parasitoid A colemani did not alter this change in distribution.