AZOSPIRILLUM POPULATIONS IN SOILS INFESTED BY A PARASITIC WEED (STRIGA) UNDER SORGHUM CULTIVATION IN MALI, WEST-AFRICA

A comparative study of Azospirillum populations in a soil infested or not by a plant parasitic weed Striga was evaluated. Most probable numb er of Azospirillum did not shaw any significant changes within the two soil samples. However, total bacterial numbers (CFU and AODC) and mic robial biomass carbon content were significantly decreased in the infe sted soil samples. Seventy two Azospirillum-like colonies were isolate d from the two soil samples. Colony hybridization using three species specific 16S rRNA oligonucleotide probes (A. brasilenselA. amazonense, A. lipoferum and A. irakense specific probes) and some selected bioch emical tests allowed the identification among these isolates of 62 iso lates as A. brasilense and 2 isolates as A. lipoferum. Azospirillum is olates from infested soil as well as from non-infested soil were genot ypically analyzed by DNA fingerprinting using ERIC PCR (Enterobacteria l Repetitive Intergeneric Consensus PCR). ERIC PCR patterns showed dif ferences between infested soil and non infested soil A. brasilense iso lates, suggesting that the parasitic plant plays a role on the genomic diversity of the bacteria.