Increase in soil pH due to Ca-rich organic matter application causes suppression of the clubroot disease of crucifers
Increase in soil pH due to Ca-rich organic matter application causes suppression of the clubroot disease of crucifers
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DOI：
10.1016/j.soilbio.2006.09.027
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发表时间：
2007-03
影响因子：
9.7
通讯作者：
R. Niwa;T. Kumei;Yoshinobu Nomura;S. Yoshida;M. Osaki;T. Ezawa
中科院分区：
文献类型：
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作者：
R. Niwa;T. Kumei;Yoshinobu Nomura;S. Yoshida;M. Osaki;T. Ezawa
由土传病原体芸苔根肿菌（Plasmodiophora brassicae）引起的十字花科植物根肿病难以防治，因为该病原体作为休眠孢子在土壤中存活很长时间。在对耕地施用有机物质影响的长期试验中发现了抑制病害和有益的土壤，并进行了研究，以澄清抑制病害所涉及的生物和非生物因素。事实上，大量的有机物，400吨-1年-1农家肥（FYM）或100吨-1年-1食品厂污泥堆肥（FSC），在抑制性土壤中掺入超过15年，这些土壤的pH和Ca浓度高于病害有益土壤，这使我们假设，由于长期掺入Ca-丰富的有机质可能是抑制病害的主要原因。我们设计了一个高度可重复的生物测定系统来检验这一假设。将抑制性土壤和有益性土壤与芸苔腐殖酸菌的休眠孢子以106孢子g-1土壤的比例混合，并将芸苔在生长室中生长8天。在显微镜下评估根毛感染的数量。结果表明，在土壤中加入2.5%（w/w）的FYM和FSC能有效地抑制病菌侵染，且FSC颗粒越细（≤ 5 mm），抑制病菌侵染和提高土壤pH的效果越好。Ca（OH）2、CaCO 3和KOH对土壤的中和作用抑制了病菌的侵染，但KOH的抑制效果不如Ca（OH）2和CaCO 3。H2SO 4酸化抑制土壤，促进了感染。利用灭菌（γ射线辐照）抑制土壤pH值研究了土壤生物区系参与病害抑制的情况。在pH值为5.5时，γ射线辐照促进了侵染，但在pH值为7.4时，无论灭菌状态如何，均未观察到侵染。所有这些观察结果表明，土壤pH值是一个主要因素，在抑制疾病的有机质的应用和钙和土壤生物在抑制土壤pH值的影响下发挥一定的作用。
Clubroot disease of cruciferous plants caused by the soil-borne pathogen Plasmodiophora brassicae is difficult to control because the pathogen survives for a long time in soil as resting spores. Disease-suppressive and conducive soils were found during the long-term experiment on the impact of organic matter application to arable fields and have been studied to clarify the biotic and abiotic factors involved in the disease suppression. The fact that a large amount of organic matter, 400tha−1yr−1farmyard manure (FYM) or 100tha−1yr−1food factory sludge compost (FSC), had been incorporated for more than 15yr in the suppressive soils and these soils showed higher pH and Ca concentration than the disease conducive soil led us to hypothesize that an increase in soil pH due to the long-term incorporation of Ca-rich organic matter might be the primary cause of the disease suppression. We have designed a highly reproducible bioassay system to examine this hypothesis. The suppressive and conducive soils were mixed with the resting spores of P. brassicae at a rate of 106sporeg−1soil, and Brassica campestris was grown in a growth chamber for 8d. The number of root hair infections was assessed on a microscope. It was found that the incorporation of FYM and FSC at 2.5% (w/w) to the conducive soil suppressed the infection and that the finer particles (⩽5mm) of FSC inhibited the infection and increased soil pH more effectively. Neutralization of the conducive soil by Ca(OH)2, CaCO3and KOH suppressed the infection, but the effectiveness of KOH was less than those of Ca(OH)2and CaCO3. Acidification of the suppressive soils by H2SO4, promoted the infection. The involvement of soil biota in the disease suppression was investigated using the sterilized (γ-ray irradiation) suppressive soils with respect to soil pH. The γ-ray irradiation promoted the infection at pH 5.5, but no infection was observed at pH 7.4 irrespective of the sterilization status. All these observations suggest that soil pH is a major factor in disease suppression by organic matter application and that Ca and soil biota play certain roles in the suppression under the influence of soil pH.