In vitro selection of rhizobacteria for increasing drought tolerance of tomato plants

This study was conducted to select native rhizobacteria (RB) isolates promising to increase tolerance of tomato plants against drought. Tomato plant samples were collected to isolate RB from both open field and protected plantations during the summer season. A total of 392 RB strains were isolated and identified by classical diagnosis tests, and their plant growth-promoting properties were determined. The RB strains were tested for drought resistance under osmotic stress induced by polyethylene glycol 6000 (PEG) at 20%. A total of 48 RB strains with higher tolerance to in vitro PEG induced drought were selected and tested for their effects on drought tolerance of tomato 'MSC-50' at seed germination stage. Seed inoculation was made as seed coating, drought stress was induced by PEG at 4%. The test was made according to ISTA rules using paper towels moistened PEG or distilled water as a control. After 14 days; the data regarding germination percentage, root length (cm), shoot length (cm) and germination % were recorded and the vigour index was calculated. Twelve RB strains resulted in an increase in vigour index under PEG induced drought conditions compared to their control. Molecular identification by 16S rRNA primers of these RB showed that 10 of tested RB strains belonged to Bacillus genus, and there was 1 RB strain from Pantoea and 1 RB strain from Pseudomonas genus. In vivo testing, these RB strains for their effects on tomato plant growing in growth chamber and greenhouse are in progress. © 2021 International Society for Horticultural Science. All rights reserved.