Increase of greenhouse tomato fruit yields by plant growth-promoting rhizobacteria (PGPR) inoculated into the peat-based growing media

The effect of some plant growth-promoting rhizobacteria (PGPR) on greenhouse tomato fruit yields was determined during a spring and a fall production. The bacteria were inoculated into commercial peat-based substrates. In the spring crop, the bacterial strains tested increased the marketable and Grade No. 1 fruit yields between 5.6 and 9.6% but these results were not statistically significant. None of the bacteria affected significantly the fruit size in this experiment. On the other hand, in the fall experiment where the plants were grown under suboptimal environmental conditions, Pseudomonas fluorescens strain 63-28 increased significantly the marketable fruit yield by 13.3% ( P ⩽ 0.1) and Grade No. 1 fruit weight by 18.2% ( P ⩽ 0.05). The average size of harvested fruits was also increased by 11.1% ( P ⩽ 0.05) in this assay and the plants treated with strain 63-28 produced 12% of unmarketable fruits as compared to 23% for the control. These results show the potential to use PGPR in order to improve yields in greenhouse tomato crops.