Growth promotion of Vigna mungo (L.) by Pseudomonas spp. exhibiting auxin production and ACC-deaminase activity

Abstract

Auxin production and 1-aminocyclopropane-1-carboxylate (ACC) deaminase of rhizobacteria are very important plant growth promoting attributes. In the present study, Pseudomonas strains exhibiting these traits were evaluated for their growth promoting effects on Vigna mungo (L.). Colorimetric analysis revealed that Pseudomonas alcaliphila Av R - 2, Pseudomonas sp. AvH-4 and Pseudomonas aeruginosa As-17, respectively, produced 40.30, 32.90 and 36.50 μg auxin ml -1 in the presence of 6% of glucose, sucrose and fructose. Similarly, Pseudomonas sp. AvH-4 expressed highest ACC-deaminase activity (355 nmol h -1) as compared to P. alcaliphila AvR-2 (115 nmol h -1) and P. aeruginosa As-17 (197 nmol h -1). Antibiotic sensitivity pattern of rhizobacteria also showed resistance against oxytetracyclin, erythromycin and penicillin. Inoculation of V. mungo with rhizobacteria positive for auxin production and ACC-deaminase activity enhanced plant growth in pot trials. In laboratory experiments (under axenic conditions), P. aeruginosa As-17 was the most effective at enhancing shoot length (70.90%), seedling fresh weight (185.70%) and root length (84.20%). Pot trials conducted under natural environmental conditions showed up to 45.60, 54.10 and 72.50% increases in shoot length, root length and number of pods, respectively, over control. © Springer-Verlag and the University of Milan 2011.