Tilemsi rock phosphate solubilizing
microorganisms and their effect on P-uptake and growth of field grown wheat in
Mali
Laval
University Quebec CANADA.
E-mail: ababana@hotmail.com
__________________
Because of the high price of imported P-fertilizers in Mali, the Tilemsi rock phosphate (TRP) is a cheaper locally available P source alternative for farmers. In many area regardless of its good physical and chemical characteristics, crops and particularly wheat showed very slow response to TRP. With the broad aim of biologically improving P uptake by wheat, in this work we describe the isolation of TRP solubilizing microorganisms and their use in field inoculation trials. In 3 different Malian wheat cultivars, 4 to 12% of the rhizosphere microorganisms were able to dissolve TRP. Six bacterial and two fungal isolates were selected for their high P-solubilizing activity in solid and liquid media, and were tested in a field in Diré in 2000-2001. Two fungal isolates Aspergillus niger (C1) and a non identified-fungus (C13) and Pseudomonas sp. (BR2) significantly increased plant heights after 6 weeks, and the fresh and dry matter yields and P-uptake after 90 days of growth. Field assays were performed in Koygour in 2001-2002. Inoculation treatments included C1, Br2, C1+Br2, and a control in the presence or absence of the AM fungus Glomus intraradices. P treatments included TRP, diammonium phosphate (DAP) and an unfertilized control. The colonization of wheat root with AM was significantly higher following inoculation with G. intraradices, and when TRP was the P source used. The presence of Pseudomonas strain BR2 improved root colonization by the AM fungus. In general, straw and grain yield improved significantly following inoculation with AM and phosphate solubilizing microorganisms. The highest P uptake by wheat grain and straw was recorded in treatment including a combinaison of AM, BR2 and C1 in the presence of TRP.