2.6. Ad planta
2.6.1. Planting material and bacterial inoculum preparation
Tomato genotypes King Kong 2 (KK2) and L390, moderately resistant and susceptible to bacterial wilt, respectively, were obtained from the Genetic Resources and Seeds Unit of the Asian Vegetable Research and Development center (AVRDC, Taiwan). A suspension of a fresh re-isolate of R. solanacearum strain To-udk2 was streaked on NGA agar medium and incubated for 48 h at 28 °C. Bacterial colonies were harvested with distilled water and the inoculum was prepared by adjusting the concentration of bacterial cells to an optical density of 0.06 at 620 nm wave length, corresponding to about 7.8 × 107 CFUm L−1.The suspensions of the selected PGPR isolates (BC1AW, BC2BA, BC3AW and BC4SS and PP3WT) were prepared accordingly with an optical density of 0.2 at 620 nm, corresponding to about 2.6 × 108 CFUm L−1.