Mechanisms of suppression of Fusarium oxysporum f. sp. raphani in soils so-called suppressive to fusarium-wilt of radish

Abstract

Suppression mechanisms involved in so-called suppressive soils to Fusarium-wilt of radish, caused by Fusarium oxysporum f. sp. raphani, were investigated. Growth and survival of the pathogen in nonrhizosphere soils were not different between so-called disease-suppressive (S) and conducive (C) soils. The growth of the pathogen on radish roots grown in S-soils was suppressed compared with C-soils, which suggested that S-soils displayed a greater degree of fungistasis than C-soils. The suppressiveness to the pathogen was removed by surface-sterilization of roots. It was therefore considered that the suppressiveness to the pathogen was due to the microorganisms colonizing the roots grown in S-soils. Estimation of microbial populations on roots suggested that the suppression may be due to antagonistic microorganisms.

Key Words:

• fungistasis
• Fusarium oxysporum f. sp. raphani
• microflora on rhizoplane
• so-called suppressive soils
• survival