Effect of indigenous bacterial isolates on the development of tomato plants grown under phosphorus deficiency

Soil microorganisms play an important role in plant growth and nutrition improving agriculture sustainability. The aim of the current study was to assess the effect of indigenous bacterial isolates inoculated in tomato seeds on plant growth under conditions of insufficient phosphorus in the growing substrate. Twelve bacterial strains, isolated onto nitrogen-free media, were used to inoculate germinated tomato seeds. Plants were grown in a growth chamber on perlite, supplemented with rock-phosphate as a sole source of phosphorus. Modified Hoagland's nutrient solution (without phosphorus (P)) was used for irrigation. An increase of 68 to 91% of the shoot fresh mass was recorded in seven treatments (with isolates Az1, Az7-Az12). Average 1.5 to 2.7-fold increase of shoot dry mass was recorded for all the tested bacterial isolates compared to the non-inoculated control. Evidences for increased availability of P were observed in Az1, Az6 and Az9 treatments although they were not effective enough to alleviate the P-deficiency in the growing substrate.