Phylogenetic diversity of the rhizobial nodulating symbionts associated to the introduced Vachellia karroo (Hayne) Banfi and Galasso (Fabaceae) in Algeria

Abstract

The diversity of rhizobia associated with the introduced woody legume flora of Algeria were rarely investigated despite their widespread distribution and agroecological and economic importance. The current research attempted to fill this knowledge gap by identifying the rhizobia species associated with Vachellia karoo seedlings cultivated in ten nurseries distributed in different bioclimatic stages all over the country. The primary objective was to understand the diversity and distribution of rhizobia species associated with this legume across different soil and climate zones. The results of our study show that despite the fact that Vachellia karoo species are located exclusively in the north part of the country under a humid and sub humid climate, the seedlings cultivated in ten nurseries distributed in different bioclimatic stages (Saharian, sub Saharian and humid) have a strong ability to grow and form nitrogen-fixing nodules regardless of the soil and climate zone. The molecular identification based on the 16S RNA gene of the 29 strains isolated and identified in the laboratory were assigned to three genera: Ensifer, Mesorhizobium and Bradyrhizobium. The genus Ensifer showed a higher occurrence (48%) and diversity compared to the two other genera and an exclusive symbiotic association with Vachellia karroo seedlings collected from nurseries located in saharian and sub saharian zones.