RESPONSE OF SORGHUM TO ARBUSCULAR MYCORRHIZAL FUNGI AND Azospirillum UNDER DROUGHT STRESS

Abstract

Beneficial microorganism can help plants to tolerate drought conditions. This work was performed under field conditions to study the effect of inoculation with arbuscular mycorrhizal fungi (AMF) Glomus intraradices and plant growth-promoting rhizobacteria Azospirillum brasilense, on the growth and grain yield of sorghum (Sorghum bicolor L. Moench) under limited soil water conditions (restricted irrigation and rainfed). In 2002 sorghum seeds were inoculated with G. intraradices and A. brasilense, planted and compared with chemical fertilization (120N-40P-00K); in 2003, AMF and nitrogen reduced fertilization (80N-00P-00K) were evaluated. In both experiments plant height and grain yield were measured. During 2002 mycorrhizal colonization was quantified, and in 2003 grain protein content was measured. In 2002, mycorrhizal colonization was higher in plants inoculated with both microorganisms. Greater grain yield was obtained when symbionts were inoculated separately. In 2003 treatments did not show any impact on plant height, and only AMF was superior (P ≤ 0.01) in grain yield. Grain protein content was increased (P ≤ 0.01) with AMF and nitrogen fertilization. G. intraradices increased (P ≤ 0.01) grain yield in both years. Restricted irrigation management promoted plant height and grain yield in both years and protein grain content in 2003, with respect to rainfed conditions, but had no effect on mycorrhizal colonization in 2002. Results demonstrated that inoculation with these symbionts might increase sorghum productivity in limited moisture soil conditions.