Molecular marker analysis of European Setosphaeria turcica populations

Setosphaeria turcica is the causal agent of northern corn leaf blight, a foliar maize disease of worldwide economic importance. In Europe, its severity increases. To investigate the pathogen's population-genetic structure in central Europe, a total of 80 isolates was sampled in Germany, Switzerland, France, Austria, and Hungary and investigated with 52 random amplified polymorphic DNA (RAPD) markers. The mating type of the isolates was determined in testcrosses. Among the 73 isolates from maize there were 26 different RAPD haplotypes. All isolates with identical haplotype are considered clonemates. The haplotype shared by most members was represented by 22 isolates from Germany, Switzerland, and France, indicating high fitness and substantial migration. Only a single clone had members in both southeastern Austria and southwestern Switzerland, suggesting that the Alps constitute a major barrier for this pathogen. Several haplotypes differed by only one or two RAPD bands from the predominant haplotype and may have arisen by mutation. Few other clonal lineages were detected. The evolution of some haplotypes could not be explained by mutation alone. Sexual recombination may rarely occur. In population samples from Germany, Switzerland, and France, mating type MAT2 was predominating, while most isolates from Austria and Hungary had MAT1. Seven isolates from Johnson grass (Sorghum halepense), an alternative host of S. turcica, were clonemates and very different in RAPD haplotypes from all isolates collected from maize.     

玉米部分自交系对丝黑穗病和大斑病的抗性鉴定

选取37份常用玉米自交系,采用人工接种的鉴定方法对丝黑穗病(Sphacelotheca reiliana)和大斑病(Exserohilum turcicum)的抗性进行评价。结果表明,不同玉米自交系对丝黑穗病和大斑病表现出不同的抗性,对丝黑穗病表现出抗病和感病的自交系分别占供试自交系的48.6%和51.4%,其中仅09杜引-1表现高抗(HR);对大斑病表现抗病和感病的自交系分别占供试自交系的35.1%和64.9%,其中仅自交系Mo17表现高抗(HR)。     

Resistance to anthracnose and turcicum leaf blight in sorghum under dual infection

A half diallel mating design was used to study the inheritance of anthracnose and turcicum leaf blight (TLB) in six sorghum cultivars. Applying pathogens inoculum separately and applying both pathogens simultaneously differently affected the reaction of each genotype. GA06/18 was resistant to both pathogens. GA06/106 x Epuripuri and MUC007/009 x Epuripuri showed high heterosis for resistance to both diseases indicating that they were good materials for sorghum breeding. Additive and non‐additive (dominance) variance components were almost equally reflected by equal contribution of both variances towards the anthracnose resistance suggesting that both additive and dominance gene effects were involved in anthracnose resistance. Contribution of additive gene effects towards TLB resistance was greater than non‐additive gene effects suggesting that additive gene effects were more important in controlling TLB resistance. This study highlighted that deployment of resistant varieties is the most cost effective way to manage both diseases especially when integrated with appropriate agronomy practices.     

利用Brn1基因分析嘴突脐孢种（Exserohilum rostratum）内变异研究

对形态变异特征较大的嘴突脐孢种Brn1基因核苷酸序列系统发育进行了分析。从系统发育树中可以看出,供试菌株与突脐孢属的其它菌种聚类在同一个分支上,与弯孢属和离蠕孢属的菌种明显区分开,形成了一个独立演化群。利用DNADIST程序计算遗传距离矩阵分析所有供试嘴突脐孢种菌株间的最小遗传距离值和最大遗传距离值分别为0.0078和0.0197,供试嘴突脐孢种菌株间的遗传距离值变化较大,但该种菌株间距离值小于系统树中种内最大遗传距离值0.0242。这一结果表明嘴突脐孢种内不同菌株间的变异属于种内变异。Brn1基因核苷酸序列分析可以用于嘴突脐孢种鉴定。     

利用Brn1基因分析嘴突脐孢种（Exserohilum rostratum）内变异研究

对形态变异特征较大的嘴突脐孢种Brn1基因核苷酸序列系统发育进行了分析。从系统发育树中可以看出，供试菌株与突脐孢属的其它菌种聚类在同一个分支上，与弯孢属和离蠕孢属的菌种明显区分开，形成了一个独立演化群。利用DNADIST程序计算遗传距离矩阵分析所有供试嘴突脐孢种菌株间的最小遗传距离值和最大遗传距离值分别为0.0078和0.0197，供试嘴突脐孢种菌株间的遗传距离值变化较大，但该种菌株间距离值小于系统树中种内最大遗传距离值0.0242。这一结果表明嘴突脐孢种内不同菌株间的变异属于种内变异。Brn1基因核苷酸序列分析可以用于嘴突脐孢种鉴定。     

玉米大斑菌(Exserohilum turcicum)和小斑菌(Helminthosporium maydis)相互关系的研究

玉米小斑病菌(Helminthosporium maydis)和玉米大斑病菌(Exseiohilum turcicum)的相互关系中,小斑病菌可强烈地抑制大斑病菌的生长,在PDA培养基上可形成明显的抑菌区,在玉米植株上能减少大斑病病斑的数目,病斑变小,产孢能力也降低。玉米小斑病菌对大斑病菌的抑制作用因不同菌株的组合而异,抑制作用的强度也随不同接种方法和培养条件而变化。根据小斑病菌对大斑病菌的抑制作用,结合小斑病菌对温度较易适应的特性,初步推断我国春玉米区有逐步发展为小斑病常发区的潜在可能性。     

Maize resistance to northern corn leaf blight is potentiated by nickel

Northern corn leaf blight (NCLB), caused by Exserohilum turcicum, is one of the most devastating diseases affecting maize yield worldwide. A foliar spray of nickel (Ni) to potentiate maize resistance against NCLB was investigated by examining alterations in the photosynthetic apparatus (leaf gas exchange and chlorophyll [Chl] a fluorescence parameters), production of ethylene and reactive oxygen species as well as activities of defence and antioxidant enzymes. Mycelial growth of E. turcicum was inhibited by Ni in vitro. Inoculated plants sprayed with Ni exhibited higher foliar Ni concentration, reduced NCLB symptoms, and lower concentrations of malondialdehyde and hydrogen peroxide. In inoculated leaves of plants not sprayed with Ni, concentrations of Chl a, Chl b, and carotenoids were lower and the photosynthetic apparatus was impaired at the biochemical level due to high NCLB severity. The activities of antioxidant enzymes were not affected by Ni, except an increase in glutathione reductase activity for noninoculated plants sprayed with Ni. High lipoxygenase and polyphenoloxidase activities, lower ethylene production, as well as elevated production of phenolics and lignin helped decrease NCLB severity in the leaves of Ni-sprayed plants.