Effect of Tilemsi phosphate rock-solubilizing microorganisms on phosphorus uptake and yield of field-grown wheat (Triticum aestivum L.) in Mali

With the broad aim of biologically improving P uptake by wheat fertilized with Tilemsi phosphate rock ( TPR), we investigated the effect of inoculation with TPR- solubilizing microorganisms isolated from Malian soils and with a commercial isolate of the arbuscular mycorrhizal ( AM) fungus Glomus intraradices ( Gi). AM root length colonization, and growth yield and P concentration of the cultivar Tetra of wheat were measured under field conditions in Mali. Experimental plots were established in Koygour ( Dire) during the 2001 - 2002 cropping season. Inoculation treatments included two fungal isolates, Aspergillus awamori ( C1) and Penicillium chrysogenum ( C13), and an isolate of Pseudomonas sp. ( BR2), used alone or in fungus-bacterium combinations in the presence or absence of the AM fungus Gi. In fertilized treatments, 0 or 30 kg P ha) 1 was applied as TPR or diammonium phosphate ( DAP). In 45-day- old wheat plants, the highest root length AM colonization ( 62%) was observed with TPR fertilized wheat inoculated with Gi and BR2. Our results suggest that BR2 is a mycorrhizal- helper bacteria and a good plant growth- promoting rhizobacteria. In fact, inoculation of wheat Tetra fertilized with TPR with a combination of Gi, BR2 and C1 produced the best grain yield with the highest P concentration. This work shows that by inoculating seeds with TPR- solubilizing microorganisms and AM fungi under field conditions in Mali it is possible to obtain wheat grain yields comparable to those produced by using the expensive DAP fertilizer.