Quesada-Moraga Enrique, Navas-Cortés Juan A, Maranhao Elizabeth A A, Ortiz-Urquiza Almudena, Santiago-Alvarez Cándido
Department of Agricultural and Forestry Sciences, ETSIAM, University of Cordoba. Campus de Rabanales. Edificio C4 Celestino Mutis, 14071 Cordoba, Spain.
Mycol Res. 2007 Aug;111(Pt 8):947-66. doi: 10.1016/j.mycres.2007.06.006. Epub 2007 Jul 3.
Factors affecting the occurrence and distribution of entomopathogenic fungi in 244 soil samples collected from natural and cultivated areas in Spain were studied using an integrated approach based on univariate and multivariate analyses. Entomopathogenic fungi were isolated from 175 of the 244 (71.7%) soil samples, with only two species found, Beauveria bassiana and Metarhizium anisopliae. Of the 244 soil samples, 104 yielded B. bassiana (42.6%), 18 yielded M. anisopliae (7.3%), and 53 soil samples (21.7%) harboured both fungi. Log-linear models indicated no significant effect of habitat on the occurrence of B. bassiana, but a strong association between M. anisopliae and soils from cultivated habitats, particularly field crops. Also, irrespective of habitat type, B. bassiana predominated over M. anisopliae in soils with a higher clay content, higher pH, and lower organic matter content. Logistic regression analyses showed that pH and clay content were predictive variables for the occurrence of B. bassiana, whereas organic matter content was the predictive variable for M. anisopliae. Also, latitude and longitude predicted the occurrence of these same species, but in opposite directions. Altitude was found to be predictive for the occurrence of B. bassiana. Using principal component analysis, four factors (1 to 4) accounted for 86% of the total variance; 32.8, 22.9, 19.6 and 10.4% of the cumulative variance explained, respectively. Factor 1 was associated with high positive weights for soil clay and silt content and high negative weights for soil sand content. Factor 2 was associated with high positive weights for soil organic matter content and high negative weights for soil pH. Factor 3 was associated with high positive weights for latitude and longitude of the sampled localities and factor 4, had high positive weights only for the altitude. Bi-plot displays representing soil samples were developed for different factor combinations and indicated that, irrespective of geographical location, absence of both fungal species was determined by alkaline sandy soils with low organic matter content, whereas heaviness of soil texture, acidity and increasing organic matter content led to progressively higher percentages of samples harbouring entomopathogenic fungi. These results could aid decision-making as to whether or not a particular cultivated or natural soil is suitable for using entomopathogenic fungi as a pest control measure and for selecting the fungal species best suited to a particular soil.
采用基于单变量和多变量分析的综合方法，研究了从西班牙自然和耕地区域采集的244份土壤样本中影响昆虫病原真菌发生和分布的因素。在244份土壤样本中，有175份（71.7%）分离出了昆虫病原真菌，仅发现了两种真菌，即球孢白僵菌和绿僵菌。在244份土壤样本中，104份（42.6%）分离出球孢白僵菌，18份（7.3%）分离出绿僵菌，53份土壤样本（21.7%）同时含有这两种真菌。对数线性模型表明，栖息地对球孢白僵菌的发生没有显著影响，但绿僵菌与耕地栖息地的土壤，特别是大田作物土壤之间存在很强的关联。此外，无论栖息地类型如何，在粘土含量较高、pH值较高和有机质含量较低的土壤中，球孢白僵菌的数量都超过绿僵菌。逻辑回归分析表明，pH值和粘土含量是球孢白僵菌发生的预测变量，而有机质含量是绿僵菌发生的预测变量。此外，纬度和经度对这两种真菌的发生也有预测作用，但方向相反。发现海拔高度对球孢白僵菌的发生有预测作用。通过主成分分析发现，四个因子（1至4）占总方差的86%；分别解释了累积方差的32.8%、22.9%、19.6%和10.4%。因子1与土壤粘土和粉砂含量的高正权重以及土壤砂含量的高负权重相关。因子2与土壤有机质含量的高正权重和土壤pH值的高负权重相关。因子3与采样地点的纬度和经度的高正权重相关，因子4仅与海拔高度有高正权重。针对不同的因子组合绘制了代表土壤样本的双标图，结果表明，无论地理位置如何，两种真菌均不存在是由有机质含量低的碱性砂土决定的，而土壤质地较重、酸度增加和有机质含量增加导致含有昆虫病原真菌的样本比例逐渐升高。这些结果有助于决定特定的耕地或天然土壤是否适合使用昆虫病原真菌作为害虫防治措施，以及选择最适合特定土壤的真菌种类。
