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Biology and management of Pythium root dysfunction in North Carolina.

机译：北卡罗莱纳州腐霉菌根功能障碍的生物学和处理。

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摘要

Pythium root dysfunction (PRD) has become an important disease of creeping bentgrass putting greens in the Southeastern U.S., yet very little is known about the etiology, epidemiology, and management of this disease. Seventy-five Pythium isolates were obtained from creeping bentgrass putting greens in NC, SC, GA, and VA. Using morphological and molecular identification techniques, 59 isolates were identified as Pythium volutum and 16 were identified as P. torulosum. A subsample of P. volutum and P. torulosum isolates were tested for pathogenicity in growth chamber experiments. All isolates of P. volutum examined were highly virulent toward creeping bentgrass roots, whereas isolates of P. torulosum were non-pathogenic. Isolates of P. volutum induced drastic reductions in creeping bentgrass root depth and root mass when infected plants were exposed to a four week high temperature regime.;Growth chamber experiments were conducted to determine the impact of temperature on infection of creeping bentgrass roots by P. volutum. This was conducted by varying the temperature during a four week infection period, after which the plants were exposed to a four week heat treatment. Symptoms characteristic of PRD developed in the 12°C, 16°C, 20°C, and 24°C infection temperature treatments, but not in the 28°C and 32°C treatments. Root depth and root mass was reduced prior to heat exposure in only the 12°C, 16°C, and 20°C treatments. After a four week exposure to 32°C/26°C (day/night), considerable reductions in root depth and root mass were observed in all infection temperature treatments except for the 28°C and 32°C treatments.;Field experiments were conducted to evaluate fungicides for preventative control of PRD. Applications of pyraclostrobin provided the best and longest lasting preventative suppression of PRD symptoms. Azoxystrobin and cyazofamid provided moderate levels of preventative suppression and the standard Pythium fungicides were not effective against PRD. In vitro assays were conducted to determine the sensitivity of P. volutum's to fungicides. Pythium volutum isolates were highly sensitive to pyraclostrobin and cyazofamid, moderately sensitive to azoxystrobin, and the least sensitive to mefenoxam.;Growth chamber experiments were performed to evaluate the effects of creeping bentgrass cultivar, organic matter content, and irrigation frequency on development of PRD. 'Crenshaw', 'Syn-96', and 'G-6' were the least susceptible cultivars when compared to 'Penncross'. The popular cultivars 'A-1' and 'A-4' were moderately susceptible and 'LS-44', 'G-2' and 'Penncross' were the most susceptible cultivars. Organic matter added at the time of establishment did not have an effect on PRD development. Symptoms of PRD were most severe when creeping bentgrass was irrigated 6 times a week when environmental conditions were conducive for infection by P. volutum. When creeping bentgrass was irrigated 3 or 4 times a week, PRD symptoms were less severe and turf quality did not decline.;Another series of growth chamber experiments were established to determine the effects of P. volutum infections on creeping bentgrass nitrate uptake, evapotranspiration, and photosynthesis. Nitrate uptake was elevated in creeping bentgrass plants that were infected with P. volutum when compared to the non-inoculated controls. Evapotranspiration was similar among inoculated and non-inoculated plants.
机译：腐霉属根部功能障碍（PRD）已成为美国东南部bent草丛生的一种重要疾病，但对该病的病因，流行病学和管理知之甚少。从在NC，SC，GA和VA上蔓延的草丛果岭中获得了75个腐霉菌分离株。使用形态学和分子鉴定技术，鉴定出59种分离物为腐霉菌，而鉴定出16种分离为假单胞菌。在生长室实验中测试了卷积假单胞菌和风疹假单胞菌分离物的子样品的致病性。所有检出的卷积假单胞菌均对蠕动的草根有极强的毒力，而圆盘假单胞菌的分离物无致病性。当感染的植物暴露于四周高温条件下时，伏牛分离株引起induced草根深和根质量的急剧降低;;进行生长室实验以确定温度对P感染infection草根的影响。体积这是通过在四个星期的感染期间改变温度来进行的，然后将植物进行四个星期的热处理。在12°C，16°C，20°C和24°C的感染温度处理中会出现PRD的症状，但在28°C和32°C的处理中则没有。仅在12°C，16°C和20°C处理中，暴露于热之前，根深和根质量会降低。在暴露于32°C / 26°C（昼/夜）4周后，除28°C和32°C处理外，所有感染温度处理均观察到根深和根质量显着降低。进行评估杀真菌剂对PRD的预防控制。吡菌胺酯的应用可提供最佳和最长的预防性抑制PRD症状的效果。嘧菌酯和cyazofamid提供了中等水平的预防抑制作用，而标准的Pythium杀真菌剂对PRD无效。进行了体外测定以确定福氏疟原虫对杀真菌剂的敏感性。腐霉腐霉对吡唑醚菌酯和氰草胺具有很高的敏感性，对唑菌酯的敏感性中等，对甲灭草胺的敏感性最低。进行了生长室实验，以评价bent草的变种，有机质含量和灌溉频率对珠江三角洲发育的影响。与“ Penncross”相比，“ Crenshaw”，“ Syn-96”和“ G-6”是最不易感的品种。流行的品种'A-1'和'A-4'为中度易感品种，'LS-44'，'G-2'和'Penncross'为最易感品种。建立时添加的有机物对珠三角的发展没有影响。当环境条件有利于卷积假单胞菌的感染时，每星期灌溉6次bent草时，PRD的症状最为严重。每周灌溉3到4次creep草时，PRD症状较轻，草皮质量没有下降。;建立了另一系列的生长室实验以确定伏地黄感染对on草的硝酸盐吸收，蒸散，和光合作用。与未接种对照相比，在感染了福氏疟原虫的ing本草中，硝酸盐的吸收增加。接种植物和非接种植物的蒸散量相似。

著录项

  • 作者

    Kerns, James Patrick.;

  • 作者单位

    North Carolina State University.;

  • 授予单位 North Carolina State University.;
  • 学科 Agriculture Horticulture.;Agriculture Plant Pathology.
  • 学位 Ph.D.
  • 年度 2008
  • 页码 144 p.
  • 总页数 144
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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