玉米圆斑病菌生理小种鉴定结果

 玉米圆斑病是我省目前大面积推广的吉单101杂交种亲本‘吉63’自交系果穗上发生的严重病害,它影响‘吉63’自交系的繁育和制种工作。     

玉米圆斑病发生调查报告

我县早在1971年发现玉米吉63自交系的果穗上有黑腐的症状。以后病情继续发展,成为配制吉单101等杂交种的主要障碍。从1979年夏开始我们对玉米圆斑病的发生、流行和防治,进行了调查和试验研究。 病原与症状 该病原菌属半知菌类、丛梗孢目、暗梗     

玉米圆斑病种子带菌问题的初步研究

玉米圆斑病菌为害玉米果穗,引起穗腐,并可随种子传播(雷切森:《种传真菌注释名录》,1979年版)。过去陕西省未见此病,后因种植带菌杂交玉米西单三号和自交系吉63带菌种子,1977年起相继在陕北洛川、黄陵等县发生。作者利用洛川的西单三号     

人工接种对新月弯孢菌侵染玉米籽粒的影响

研究了人工接种不同接种时期和方法对新月弯孢菌侵染玉米籽粒的影响,结果表明:玉米弯孢叶斑病菌可以侵染玉米果穗籽粒,使玉米籽粒产生褐色病斑。伤口接种法能使玉米果穗100%发病;花丝通道接种也可导致果穗发病,但其发病频率很低;而花丝喷雾接种和苞叶喷雾接种病菌不能成功侵染玉米果穗籽粒;吐丝后10 d和乳熟期接种只能引起接种点籽粒发病,病菌扩展不好;但籽粒形成期接种的玉米果穗籽粒不仅接种点发病,而且其周围的籽粒也感染了病菌,病菌扩展情况较好。试验明确,玉米籽粒形成期采用伤口接种是使玉米籽粒发生弯孢叶斑病的一种较为理想的人工接种方法。     

受玉米大斑病菌侵染后玉米抗感近等基因系SOD动态变化的研究

 以玉米抗、感大斑病菌近等基因系为材料,研究了玉米抗病系和感病系在接种玉米大斑病菌后SOD活性和SOD同工酶谱的动态变化。结果发现,在病原菌侵染初期携带显性抗病单基因的抗病系SOD活性一般呈下降趋势,明显地低于不携带任何已知抗病基因的感病近等基因系;在病原菌侵染中、后期却较大幅度上升,反而逐渐明显地高于感病近等基因系。在HZ1遗传背景中Rf值为0.25的SOD同工酶酶带,与Ht2和HtN等抗病基因的作用有关。本文认为SOD及有关活性氧代谢在玉米对大斑病菌抗性中可能具有重要的作用。     

环境与寄主条件对玉米灰斑病菌侵染寄主的影响

利用玉米灰斑病菌株20-47、感病玉米品种(掖单13)和抗病玉米品种(沈单10号),在人工气候室和自然条件下对影响玉米灰斑病菌侵染的环境条件和寄主生育期进行了研究。结果表明:玉米灰斑病是属偏高温高湿类型的病害,在温湿度条件不能得到满足时,病害就难以完成侵染发病;病菌接种侵入的最佳温度为25℃左右,水滴条件下侵染最容易;土壤条件特别是氮、磷肥如果施用不均匀、不足或过多,也都可以对结果产生影响,在通常情况下,增施氮、磷肥能提高玉米对灰斑病的抗性;在一定光照强度范围内,光对鉴定结果的影响不明显,但光暗交替更有利于寄主发病;寄主不同生育期对病原菌侵染寄主的影响不同,11～12叶期(喇叭口期)接种,病菌较易侵染。     

玉米穗粒腐病接种技术及品种抗病性鉴定

以玉米穗粒腐病的优势病原菌串珠镰刀菌Fusarium moniliforme为接种菌源,采用4种接种方法进行比较,以针刺果穗较深处(籽粒与穗轴间)发病最重,花丝喷雾法发病最轻;接种时期以玉米乳熟期接种为好;接种浓度10×40倍下每视野60个分生孢子;接种量以每果穗接种2.5ml孢子悬浮液发病最重。同时规范了病情分级标准及品种抗、感程度划分标准。采用规范程序,对63份玉米自交系及杂交种进行了抗病性鉴定。     

安徽省玉米小斑病菌生理小种鉴定及对烯唑醇的敏感性

玉米小斑病是由玉蜀黍双极蠕孢(Bipolarismaydis)引起玉米叶部发病的病害之一,该病害广泛分布在世界玉米产区,严重影响玉米生产。玉米小斑病菌存在明显生理分化现象,目前已证实在中国存在T、C、S和O共4个小种。由于近年来不育细胞质的感病玉米自交系在玉米育     

八个玉米自交系对小斑病(O小种)田间成株期水平抗性因素的观察研究

 根据田间抗病性鉴定结果,选取高抗系齐31和凤白29(新),抗病系威风322和黄早4,中抗系获白,中感系黄204,感病系替423和罗31等八个玉米自交系,对玉米小斑病(Helminthosporium maydis)(O小种)田间成株期水平抗性因素的观察研究。在自然发病条件下,无论在病斑的面积,单位病斑面积上的产孢量或发病始期的病斑数量来看,八个自交系间都存在显著差异(P=0.01)。可是每个因素与田间抗病程度之间看不出有什么相关性。如果把三个因素乘积进行相关性测定,成株期抗病性与水平抗性三个因素乘积之间呈现高度相关性(r=0.85,P=0.01)。     

扎兰屯市玉米丝黑穗病流行原因分析及防治建议

一、病害流行原因分析１．近年来,我地大豆重迎茬减产,加之大豆市场价格又降低。于是,玉米面积扩大,并引进了感病的桦单３２品种,以致菌量逐年增长,寄主感病群体加大。当环境条件适合病害发生,便可造成流行。２．春季干旱、气温高、玉米感病期长,有利于病菌侵入玉米丝黑穗病属于积年流行病害。当玉米播种后（５月上旬）,从种子开始萌动至五叶期（６月上旬）都能受病菌侵染,特别是幼芽期侵染率最高。此期土壤温、湿度条件与发病的关系最为密切。病菌侵入适温在２５℃左右,适宜的土壤湿度在２０％。故春旱年份,常为病害的流行年。…     

玉米丝黑穗病防治研究

玉米丝黑穗病是白城地区的重要病害,一般发病率为3—5%,重者高达30%以上,是生产上急待解决的问题。其症状以正常型为主,有时出现矮化型、矮化丛生型和多分蘖型等特异症状。病株以雌穗为黑穗、雄穗为健穗及雌雄穗皆为黑穗者居多。病穗上自然脱落的厚垣孢子萌发率高,病穗内的萌发率明显降低。此病为系统侵染病害,种子及土壤均可带菌传病,以土壤带菌为主,属土传病害。厚垣孢子在土壤里能存活三年,土壤带菌量越多,菌土覆盖种子越厚,发病率越高。丝黑穗病菌侵染玉米幼苗时间较长,从种子萌芽到四叶期最易侵染,五叶期后,侵染明显下降,八叶期后不再侵染。在幼苗叶片上接菌不能侵染致病。玉米丝黑穗病菌不能侵染高梁。高梁丝黑穗病菌能侵染玉米,但侵染率甚低。侵染玉米后的病菌,不再侵染高梁,只侵染玉米,且致病力明显增强。两菌是同一菌种的不同生理型。用来自九个省、市的丝黑穗病菌接种于不同抗性的自交系鉴定寄主,其致病力不同,陕西和新疆的致病力弱,辽宁和吉林的致病力强。在田间人工接种条件下,鉴定了二百余份自交系和杂交种的抗病性,品种间有明显差异,高抗的近于免疫,高感的发病率在90%以上。抗病性遗传规律表现为双亲高抗的,其后代亦抗,以母本的抗病性起主导作用。选百余种农药处理种子,筛选结果:个别药剂防效有高达70%以上者,但年度间效果不稳定,多数药效稳定在50%左右。     

Gametic phase disequilibria in populations of race 2 and race 3 ofCochliobolus carbonum

Over 3 years 15 samples ofC. carbonum were collected from 11 corn fields in North Carolina and Tennessee. Among 514 isolates of race 2 and 319 isolates of race 3, five phenotypic characters (mating type, production of pseudothecia, production of asci and ascospores, tolerance to cycloheximide and carboxin, respectively) that are controlled by single genes at unlinked loci (Mat, Psu, Asc, Cyh, Crb) were examined. Gametic phase disequilibrium (GPD) was analyzed by three methods. First, observed and expected four-locus haplotype frequencies were compared inG-tests for goodness of fit (method 1) and second, four-locus disequilibrium was calculated using an index of association which is based on the variance of the number of loci at which two isolates in a given population differ (method 2). Third, observed and expected frequencies of allele pairs were compared in 2×2 contingency tables (method 3). Each test was performed on individual and pooled samples which also allowed assessment of heterogeneity among samples. In general this heterogeneity was low, i.e. the consistency of associations among samples was high. Four-locus disequilibrium was significant in race 2 with method 1 but not with method 2. In race 3 we found no disequilibrium with any of the two methods. Method 3 indicated that several allele pairs were significantly associated in race 2 but not race 3. Thus GPD was significant in race 2 but not in race 3. Mating type frequencies were close to 0.50 in race 2 and race 3. This and the non-significant index of association indicate that the sexual stage ofC. carbonum is operating within each of the two race populations. It is suggested that selection favours different haplotypes in the asexual than in the sexual stage of the pathogen. Such disruptive selection may have maintained polymorphisms of genes related to sexual fertility and stabilized gene frequencies inC. carbonum over a period of 15 years (1972–1987).     

玉米自交系对亚洲玉米螟抗性评价初报

在相同田间条件下,用接种方法评价了一些玉米自交系对第一代亚洲玉米螟[Ostrinia furnacalis(Guenee)]的抗性。经鉴定抗螟的有L105、75—242、B75、W59E、404、黄早4、A662、C131A和4004等。它们与感虫自交系比分别减少螟虫幼虫57.8、64.4、55.6、37.8、50.0、71.4、64.3、0和20%,茎蛀孔减少68.3、61.9、55.6、38.1、63.8、57.4、72.3、66.0和47.6%,隧道长度分别减少70.1、77.5、53.2、34.6、71.3、76.6、40.7、77.0和32.9%。茎折、穗和穗柄被害比感虫自交系也明显减轻。     

鞘腐病发生程度与玉米倒伏及产量损失间的相关性分析

为深入探讨鞘腐病的发生对玉米倒伏及产量的影响,通过温室接种法测定了玉米不同发育阶段鞘腐病的发病程度及相关防御酶活性,以确定玉米鞘腐病的易感时期;并通过田间接种不同浓度的层出镰孢菌获得不同发病级别的玉米鞘腐病病株,于乳熟期调查病害发生程度,利用YYD-1B数显植物茎秆强度检测仪测定每株玉米茎秆的抗倒伏能力,收获后测定其产量。结果显示,玉米鞘腐病的易感时期为开花期,郑单958和浚单20在此时期鞘腐病的发病率分别为64.36%和40.22%;病情指数分别达42.73和19.58,均高于其它时期;玉米自交系OH43Ht1、郑58和杂交品种郑单958的茎秆抗倒伏能力均随着玉米鞘腐病发病级别的升高而降低;郑58和郑单958的产量随玉米鞘腐病发病级别的升高而降低,每公顷产量损失郑58从13.84%增加到29.53%、郑单958从3.99%增加到16.72%。表明玉米鞘腐病严重发生时能够降低玉米的抗倒伏能力和产量,且对自交系的影响大于杂交品种,生产中应引起高度重视。     

Leaf and stem blight ofEuphorbia geniculata incited byBipolaris zeicola

Recently leaf and stem blight disease was observed onEuphorbia geniculata Orteg. The pathogen was isolated in pure culture and identified asCochliobolus carbonum Nelson (anamorph:Bipolaris zeicola (Stout) Shoem. =Helminthosporium carbonum Ullstrup). This is the first record of this fungus causing leaf and stem blight disease onE. geniculata. In a greenhouse study, none of 19 other plant species tested showed pathogenic reactions. The specific host range and highly virulent nature ofB. zeicola onE. geniculata indicated that this pathogen has potential for use as a biocontrol agent forE. geniculata.     

Biochemical response of inbred and hybrid corn (Zea mays L.) to R-25788 and its distribution with EPTC in corn seedlings

The average endogenous GSH content of eight lines of inbred corn was almost twofold greater than ten varieties of hybrid corn. When inbred and hybrid corn lines were treated with R-25788, the average GSH content increased by 56 and 95%, respectively. R-25788 protected two special inbred corn lines, GT 112 (atrazine susceptible) and GT 112 RfRf (atrazine resistant) from EPTC injury by increasing the GSH content and GSH S-transferase activity in roots. Most of the radiolabel from [¹⁴C]R-25788-treated plants remained in the root tissues whereas the radiolabel in [¹⁴C]EPTC-treated plants was evenly distributed between foliar and root tissues. From radiolabel experiments, hybrid corn seedlings were found to absorb more R-25788 from soil than EPTC. There was no difference between inbred and hybrid corn in the amounts of R-25788 or EPTC taken up or in the enhancement of GSH S-transferase activity caused by R-25788.     

Maize seed chitinase is modified by a protein secreted by Bipolaris zeicola

Plants contain defense mechanisms that prevent infection by most fungi. Some specialized fungi have the ability to overcome plant defenses. The Zea mays (maize) seed chitinase ChitA has been previously reported as an antifungal protein. Here we report that ChitA is converted to a modified form by a protein secreted by the ear-rot pathogen Bipolaris zeicola (Holomorph = Cochliobolus carbonum). In denaturing chitinase zymograms, ChitA activity was detected in protein extracts from healthy seeds, but not in those from diseased seeds of ears that had been inoculated with B. zeicola. Furthermore, addition of proteins from diseased seeds to those from healthy seeds resulted in the loss of detectable ChitA activity. This indicated that protein extracts from diseased seeds contained a molecule that targets ChitA. We determined that this molecule is a secreted protein we term B. zeicola chitinase modifying protein (Bz-cmp). We purified ChitA from maize seed and Bz-cmp from sterile cultures of B. zeicola. Biochemical experiments demonstrated that Bz-cmp catalytically converts ChitA into a modified form that has reduced molecular mass in SDS-PAGE gels. Native chitinase zymogram analysis of modified and unmodified ChitA demonstrated that, contrary to our initial observation, Bz-cmp does not impair ChitA's chitinase activity but rather its chitin-binding ability. Our findings suggest that ChitA is an important component of defense in developing maize seeds and identifies Bz-cmp as a potential contributor to pathogenicity.     

玉米丝黑穗病原菌侵染的一些细胞学研究

 在玉米生育早期,以幼芽鞘为材料,对11个抗病性不同的自交系进行了研究。玉米丝黑穗病原菌[Sphacelotheca reiliana (Kühn) Clint var.zeae Pass]可在玉米幼芽鞘内表皮上生长和繁殖;其侵染菌丝可直接侵入表皮细胞或通过气孔进入寄主体内。菌丝的侵入诱导了芽鞘内表皮细胞的细胞壁、细胞质和细胞膜特性的异常变化;抗性不同的自交系对病原菌侵入的反应不同,揭示了在生育早期玉米芽鞘细胞就表现了其固有的抗病性。     

Antibiosis of maize inbred lines to the carmine spider mite, tetranychus cinnabarinus

The antibiosis of tenZea mays L. inbred lines to the carmine spider mite,Tetranychus cinnabarinus (Boisduval) (Acari: Tetranychidae), was evaluated. Two maize inbred lines previously reported as resistant to this spider mite and a susceptible inbred line were compared with B96 (formerly called 41:2504B), reported as being resistant to the two-spotted spider mite T. urticae and to the European corn borer (Ostrinia nubilalis Hübner). Other lines were derived from B96. All lines originated in the U.S.A. and were tested in Israel at two different growth stages. Four days after inoculation of detached leaf squares with adult mites, significant differences in susceptibility were observed among lines. At the 3-leaf stage lines B68, B96, B79, A619, B65, B49 and B64 reduced the average mite daily fecundity by 43%, 64%, 66%, 67%, 77%, 81% and 87%, respectively, as compared with the most susceptible line, B52. At the flowering stage, the average reduction in mite daily fecundity was much lower: inbred lines B64, A619 and B96 reduced the average mite daily fecundity by 48%, 51% and 86%, respectively, whereas the seven other genotypes had an intermediate or a susceptible reaction to the carmine spider mite, with A661 being the most susceptible. Our results show that B96 could be used as a source of resistance in developing improved resistance of inbred lines of maize to carmine spider mites.     

Genetics of resistance to downy mildew in Brassica oleracea and breeding towards durable disease control for UK vegetable production

Downy mildew resistance was previously identified from screening a Brassica oleracea collection against two standard UK isolates of Hyaloperonospora parasitica. Sources of resistance were chosen from this material and developed further in this study by generating doubled haploid (DH) and inbred lines. Seedlings from the new lines were tested for resistance to a larger collection of H. parasitica isolates collected in 2001–2002 and 2007–2008 from the main broccoli and cauliflower production regions of the UK. Three lines (derived from borecole or summer cabbage) were broadly resistant to the pathogen isolates. Three of the remaining lines exhibited strong isolate‐specific resistance; several examples of weak or basal level of resistance to some isolates were observed. A new H. parasitica variant collected in 2008 was virulent in the broadly resistant lines, but was avirulent in a line with narrow specificity of resistance. The F₂ and BC₁ seedlings derived from outcrossing each of the three broadly resistant lines to susceptible broccoli and cauliflower lines segregated in a manner indicating that the resistance was controlled by a single dominant gene. No susceptibility was observed amongst F₂ seedlings derived from intercrossing the three resistant lines, indicating that they all share the same or closely linked broad‐spectrum resistance gene(s). DH lines were produced from F₁ plants, and resistant plants were further backcrossed to produce broccoli and cauliflower‐like lines that could be useful pre‐breeding material. A combination of resistance from lines with broad and narrow specificity is recommended for controlling downy mildew in UK brassica production.