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Determination and Analysis of Soil Receptivity to Fusarium solani f. sp. pisi Causing Dry Root Rot of Peas. P. J. Oyarzun, Department of Soil Ecology, DLO Research Institute for Plant Protection (IPO-DLO), P. O. Box 9060, 6700 GW Wageningen, Netherlands; G. Dijst, and P. W. Th. Maas. Department of Soil Ecology, DLO Research Institute for Plant Protection (IPO-DLO), P. O. Box 9060, 6700 GW Wageningen, Netherlands. Phytopathology 84:834-842. Accepted for publication 10 May 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/Phyto-84-834.

A procedure was developed to differentiate field soils according to their receptivity, ranging from suppressive to conducive, to Fusarium solani f. sp. pisi, one of the most important soilborne fungi causing dry root rot of pea. Experiments were carried out with samples of natural soil collected from commercial fields that had had a low inoculum potential for root rot in peas in previous years. In bioassays with computer-controlled soil water potential, light intensity, air temperature, and relative humidity, dry root rot severity responses to a range of inoculum levels were determined. Disease severity in different soil samples at the same infestation level showed that soil as a substrate strongly affects the inoculum potential of F. s. pisi. In samples that were selected because they produced only dry root rot, the amount of native Fusarium in pea rhizosphere soil was uncorrelated with root rot severity. Univariate and multivariate models were examined for their adequacy to describe and compare disease response data. Principal component analysis carried out on a table of samples by Weibull fitted disease responses or on a table of samples by average disease responses produced a similar receptivity order (P ≤ 0.01) of the samples, but fitted values increased the quality of ordinations. Use of cluster analysis followed by a canonical variate analysis classified the tested soil into groups that differed significantly (P ≤ 0.05 on the basis of x2) in soil receptivity to F. s. pisi. The value of this technique for further ecological research is discussed.