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首页> 外文学位 >Cultural and biological control methods for Phytophthora root rot in Fraser fir.
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Cultural and biological control methods for Phytophthora root rot in Fraser fir.

机译：弗雷泽冷杉的疫霉根腐病的文化和生物防治方法。

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摘要

Phytophthora root rot of Fraser fir caused by Phytophthora cinnamomi and several other Phytophthora spp. is a severe problem in Christmas tree production. Since fungicides are ineffective in disease control and host resistance is not yet available, cultural control methods are under investigation as a means of reducing disease pressure on infested production sites. Mulching systems with raised beds of pine bark, wood chips, or wood chips blended with compost were tested, along with compost or sulfur as soil amendments, at five sites spanning the western North Carolina growing region. Microbial populations and activity in soils and mulches were characterized over a two year period, using dilution plating with calculation of a log series diversity index for counts of bacteria, fungi, and cellulose-degrading micoorganisms, analysis of fluorescein diacetate hydrolysis for estimation of total microbial activity, and quantification of reducing sugars after incubation with carboxymethyl-cellulose for estimation of total cellulase enzyme activity. Bacterial and fungal counts, microbial activity, and cellulase activity were higher in mulch than in soil at all sites and times (P0.01), and generally did not differ among mulch types nor among soils. Treatments significantly affected disease ratings and tree survival at three of five sites, with one or more mulch treatments yielding lower disease ratings and greater survival than controls. Tree mortality at each time point varied significantly with cellulase activity in the upper portion of the root zone (P=0.005). Other biological variables did not show significant relationship with disease ratings or mortality.;To further investigate the role of cellulase enzymes in suppression of P. cinnamomi, a commercial formulation of cellulase was used to generate a standard curve which could be used to correlate cellulase activity levels in field samples with the enzyme unit concentrations commonly used in laboratory studies. Two isolates of P. cinnamomi were exposed to a range of enzyme concentrations, and data were collected on biomass and sporangia production. Cellulase exposure reduced sporangia production but did not reduce biomass within the range analogous to that observed in field-applied mulch. In a bioassay with lupine, cellulase applied to soil containing infested root fragments did not reduce disease progress.;Container trials were also used to assess the impacts of a wide range of organic and inorganic amendments on Phytophthora root rot in Fraser fir seedlings, and to examine the contributions of compost, microbial inoculants, and isolates of cellulytic fungi to disease suppression in wood chip mulches. In trials with wood chips blended into soil and trials with seedlings planted directly into wood chip mulch, seedling survival was greater when wood chips were amended with compost, a soil inoculant, or a biocontrol agent. If wood chips were amended with compost, the addition of a cellulytic fungus, including a known biocontrol agent, did not further enhance plant survival, and in most cases did not significantly increase cellulase activity over compost amended wood chips alone.
机译：由肉桂疫霉菌（Phytophthora cinnamomi）和其他几种疫霉菌（Phytophthora spp）引起的弗雷泽冷杉的疫霉根腐病。在圣诞树生产中是一个严重的问题。由于杀真菌剂在疾病控制方面无效，并且宿主抗性尚不可用，因此正在研究培养控制方法，以减轻感染的生产场所的疾病压力。在北卡罗来纳州西部种植区的五个地点，测试了带有松树皮，木屑或木屑与堆肥混合的高架床的覆盖系统，以及堆肥或硫作为土壤改良剂。在两年的时间内对土壤和覆盖物中的微生物种群和活性进行了表征，使用稀释平板计算对数序列多样性指数以计算细菌，真菌和降解纤维素的微生物数量，分析双乙酸荧光素水解以估算总微生物量羧甲基纤维素孵育后的还原酶活性和还原糖的定量，以评估总纤维素酶的活性。覆盖物的细菌和真菌计数，微生物活性和纤维素酶活性在所有地点和时间均高于土壤（P <0.01），并且在覆盖物类型之间和土壤之间通常没有差异。在五个位置中的三个位置，治疗显着影响疾病评级和树木存活率，一种或多种覆盖处理的疾病评级和存活率均高于对照组。在每个时间点的树木死亡率随根区上部的纤维素酶活性而显着变化（P = 0.005）。其他生物学变量与疾病等级或死亡率没有显着关系。；为了进一步研究纤维素酶在抑制肉桂肉桂酸杆菌中的作用，使用商业化的纤维素酶制剂生成一条标准曲线，该曲线可用于关联纤维素酶活性实验室研究中通常使用的酶单位浓度测定田间样品中的水平。将两个P. cinnamomi分离株暴露于一定浓度的酶中，并收集了有关生物量和孢子囊产量的数据。纤维素酶的暴露减少了孢子囊的产生，但并未降低生物量，其范围类似于在田间覆盖的覆盖物中观察到的范围。在使用羽扇豆进行的生物测定中，将纤维素酶应用于含有受侵染的根部片段的土壤不会降低病害进展。还使用了容器试验来评估各种有机和无机改良剂对Fraser fir幼苗中疫霉菌根腐病的影响，以及检查堆肥，微生物接种剂和纤维素分解真菌分离物对木片覆盖物中疾病抑制的贡献。在将木片混入土壤的试验和将幼苗直接种植在木片覆盖物中的试验中，用堆肥，土壤接种剂或生物防治剂改良木片后，幼苗的存活率更高。如果用堆肥改良木片，则添加纤维素分解真菌（包括已知的生物防治剂）不会进一步提高植物的存活率，并且在大多数情况下，与单独使用堆肥改良的木片相比，纤维素酶活性不会显着提高。

著录项

  • 作者

    Richter, Brantlee Spakes.;

  • 作者单位

    North Carolina State University.;

  • 授予单位 North Carolina State University.;
  • 学科 Agriculture Plant Pathology.;Agriculture Soil Science.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 108 p.
  • 总页数 108
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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