Étude comparative de la flore bactérienne de la rhizosphère de deux cultivars de palmier dattier sensible et résistant à la fusariose

Abstract

This report deals with the qualitative and quantitative distributions of bacterial populations in the rhizosphere of two date-palm cultivars, one sensitive and one resistant to fusariosis, and with the antagonistic capacity of these bacteria against the pathogen Fusarium oxysporum f.sp. albedinis. In the external zones of young roots, bacterial growth was stimulated more by the sensitive cultivar than by the resistant one. A survey of 665 isolates permitted the bacteria to be grouped in two main genera, Pseudomonas and Bacillus, and in a coryneform group composed of Arthrobacter, Brevibacterium, and Pimelobacter. The generic and specific composition differed between the two cultivars and varied with root age (young or old) and the root zones considered (internal or external). In external zones, Pseudomonas caryophylli and Pseudomonas gladioli were the most abundant for the sensitive cultivar. In the endorhizosphere, Bacillus firmus was more abundant in the resistant cultivar, and Pseudomonas fluorescens biovar II in the sensitive one. Difference were also noted in the percentages of antagonistic bacteria against F.o. albedinis. The present study confirms the findings of several authors that plants are capable of controlling their own rhizosphere bacterial populations.Key words: bacteria, rhizosphere, systematics, fusariosis, date palm.[Journal translation]