Corrélations entre l'aptitude de différentes souches de Fusarium à limiter la fusariose vasculaire du lin, leur activité respiratoire et leur développement saprophytique dans un sol désinfecté

Abstract

Correlations between two ecophysiological traits of 13 Fusarium strains (viz., ability to develop saprophytically in a disinfected soil and respiratory activity) and their capacity to protect a flax crop from vascular fusariosis were established for one soil type. The ability of Fusarium strains to reduce the severity of the disease (efficiency) differed greatly. The most competent ones lowered the death rate by 80%, while the least competent had virtually no effect. Classification based on strain efficiency differed depending on whether it was performed on disinfected soil or on soil not heat treated. When the abilities of strains to colonize disinfected soil were estimated by enumeration on agar plates, Fusarium oxysporum strains proved superior to Fusarium solani due to their production of more numerous conidia, and therefore greater numbers of colonies, without significantly increasing biomass. Respiratory activity ranged from moderate to low. A clear, positive correlation was found between the respiratory activity and the efficiency of the strains grown in untreated soil, while the correlation was not significant in the disinfected soil. In the latter case, however, efficiency was correlated with the saprophytic development of the strains. [Journal translation]