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首页> 外文OA文献 >Emerging issues in the U.S. Corn Belt: infection of corn by Clavibacter michiganensis subsp. nebraskensis and use of foliar fungicides to protect yield
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Emerging issues in the U.S. Corn Belt: infection of corn by Clavibacter michiganensis subsp. nebraskensis and use of foliar fungicides to protect yield

机译：美国玉米带中出现的新问题：密歇根州立克氏杆菌亚种感染玉米。内布拉斯加州和使用叶面杀菌剂保护产量

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Currently two major issues pertaining to disease management in corn production in the US Corn Belt are the spread of Goss\u27s wilt and leaf blight caused by Clavibacter michiganensis subsp. nebraskensis (Cmn), and the use of foliar fungicides on corn for `plant health\u27 benefits. This dissertation presents data regarding infection of corn by Cmn, and fungicide effects on disease management and yield.Greenhouse and laboratory research was undertaken to determine if infection of corn by Cmn may occur without severe wounding, such as that caused by hail, sand blasting or wind damage. Corn plants with no obvious wounding were spray inoculated with a suspension of Cmn (~108 cfu/ml) and compared to plants that were wounded and spray inoculated. The incidence of Goss\u27s wilt and leaf blight on non-wounded inoculated plants was 37.0% and 60.0% under ambient and increased humidity conditions, respectively compared to 100% incidence on plants that were wounded and inoculated with the pathogen. Leaf wash assays showed populations of epiphytic Cmn survived and increased over time on corn leaves. Fluorescence and scanning electron microscopy (SEM) revealed that Cmn colonized leaves in localized sites including the junctions between epidermal cells, cuticle depressions, in and around stomata, and at the bases of glandular trichomes. Furthermore, single cells and aggregates of Cmn were observed within substomatal chambers using SEM. We propose that sites of epiphytic Cmn localization such as stomata and trichome bases may serve as infection courts for Cmn in the absence of severe wounding.Field research was conducted from2010 to 2012 at multiple locations in the Corn Belt to assess the effects of fungicide application timing on disease development and yield of hybrids that varied in susceptibility to Cercospora zeae-maydis (Czm) and Setosphaera turcica (St), cause gray leaf spot (GLS) and northern corn leaf blight (NCLB), respectively. A standard experimental design and set of treatments (hybrid, multiple pathogen inoculation types and timing and fungicide applications timing) were used in all four states (Illinois, Iowa, Ohio and Wisconsin). Generally foliar disease severity was low, final severities in the non-sprayed control were less than 5% at all site years except for Illinois in 2010 and 2011 (disease severity ranged from16 - 22%). Fungicide application (VT/ R1) significantly reduced disease severity relative to the control in five of eight site years (P \u3c0.05). Disease was reduced by 30% at Wisconsin in 2011, by approximately 20% at Illinois in 2010, 29% at Iowa in 2010, and 32% and 30% at Ohio in 2010 and 2012, respectively. The untreated control had significantly lower yield (P \u3c0.05) than the fungicide-treated in three site-years. Fungicide application increased the yield by approximately 6% at Ohio in 2010, 5% at Wisconsin in 2010 and 6% in 2011. Yield differences ranged from 30- 550 kg /ha and could not consistently be attributed to benefits related to physiological processes enhanced by the use of fungicides. Results suggest susceptibility to disease and prevailing environment are important drivers of observed differences among treatments and sites.A case study teaching resource that communicates a grower\u27s decision-making process when considering the application of foliar fungicides in corn was developed and presented to students at Iowa State University in an introductory plant pathology course. The case study presentation is designed for a 50 minute class session, using both a small group and whole-class review and discussion style. Students were also given the opportunity to write a 140 character \u22tweet-like\u22 statement, comment or question for an expert. Tweeting enhanced discussion and enabled the instructors to moderate discussion, connect student ideas to the lesson and inform the entire class on issues raised related to corn production in the US Corn Belt such as scouting, fungicide application, break even prices and physiological processes enhanced by fungicides. More than 80% of the students appreciated the \u22real life scenario\u22 approach and felt it enhanced their appreciation of the issue.
机译：当前，在美国玉米带中，与玉米生产中的疾病管理有关的两个主要问题是密歇根州立克氏杆菌亚种引起的戈斯枯萎病和叶枯病的蔓延。内布拉斯加州（Cmn），以及在玉米上使用叶面杀菌剂以促进植物健康。这篇论文提供了有关Cmn对玉米的感染以及杀真菌剂对疾病管理和产量的影响的数据。温室和实验室研究确定了Cmn对玉米的感染是否可能在没有严重伤害的情况下发生，例如冰雹，喷砂或风的损害。将没有明显伤口的玉米植株用Cmn（〜108 cfu / ml）悬浮液喷雾接种，然后与受伤和喷雾接种的植株进行比较。在环境和湿度增加的条件下，未受伤的接种植物的戈斯枯萎和叶枯病的发生率分别为37.0％和60.0％，而受伤和接种病原体的植物的发生率为100％。洗叶试验表明，附生Cmn种群在玉米叶片上存活并随时间增加。荧光和扫描电子显微镜（SEM）显示，Cmn定植在局部位置的叶片，包括表皮细胞，表皮凹陷，气孔内和周围以及腺毛的基部之间的交界处。此外，使用SEM在气孔下腔室内观察到了Cmn的单细胞和聚集体。我们建议在没有严重伤害的情况下，将附生的Cmn定位部位（例如气孔和毛状体基部）用作Cmn的感染场所.2010年至2012年在玉米带的多个位置进行了现场研究，以评估杀菌剂施用时机的影响玉米（Czm）和黑粉菌（Stosphaera turcica）（St）易感性各不相同的杂交种的病害发展和产量，分别导致灰叶斑病（GLS）和北方玉米叶枯病（NCLB）。在所有四个州（伊利诺伊州，爱荷华州，俄亥俄州和威斯康星州）均使用了标准的实验设计和一套处理方法（混合，多种病原体接种类型，时机和杀菌剂施用时机）。一般而言，除2010年和2011年的伊利诺伊州外，在所有地点，叶面疾病的严重程度均较低，未喷雾对照的最终严重度均低于5％（疾病严重程度为16-22％）。相对于对照组，在八个位点的五年中，杀菌剂的施用（VT / R1）显着降低了疾病严重程度（P \ u3c0.05）。 2011年，威斯康星州的疾病减少了30％，2010年在伊利诺伊州减少了约20％，2010年在爱荷华州减少了29％，2010年和2012年在俄亥俄州减少了32％和30％。在三个位点年中，未处理的对照的产量（P \ u3c0.05）显着低于杀菌剂处理的产量。施用杀真菌剂使俄亥俄州的产量在2010年增加了大约6％，在威斯康星州增加了5％，在2010年增加了6％，在2011年增加了6％。产量差异介于30-550千克/公顷之间，不能始终归因于与增强生理过程有关的收益使用杀菌剂。结果表明对疾病和流行环境的易感性是观察到不同处理方法和地点之间差异的重要驱动因素。开发了一个案例研究教学资源，该方法传达了种植者在考虑使用玉米叶面杀菌剂时的决策过程，并向爱荷华州立大学植物病理学入门课程。案例研究演示文稿设计为一个50分钟的课程，使用小组讨论和全班讨论和讨论方式。学生也有机会为专家撰写140个字符的\ u22tweet式\ u22陈述，评论或问题。发推文加强讨论，使讲师能够进行讨论，将学生的想法与课程联系起来，并向全班介绍与美国玉米带玉米生产相关的问题，例如侦察，杀菌剂施用，收支平衡和杀菌剂增强的生理过程。超过80％的学生赞赏“现实生活中的情景”方法，并认为它增强了他们对该问题的理解。

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    Obura, Salome Mallowa;

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  • 年度 2015
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