Enhancement of Tomato Seed Germination and Growth Parameters through Seed Priming with Auxin-Producing Plant Growth Promoting Bacteria Strains

The use of microbial seed priming may be a promising tool to improve the first stages of seed germination of several herbaceous species. In tomatoes (Solanum lycopersicum L.), enhanced germination and vigor, and biotic and abiotic stress control, with a reduction in chemicals, have been reported. In this study, seeds from two Italian tomato varieties (Canestrino di Lucca and Pisanello) were primed with seven different strains of plant growth-promoting rhizobacteria (PGPB) belonging to Azospirillum baldaniorum, A. brasilense, Methylobacterium symbioticum, Bacillus amyloliquefaciens, B. licheniformis, and B. subtilis. They were selected for their ability to produce auxin. The germination test was carried out on treated seeds and the germination percentage was calculated. The obtained seedlings were transplanted and kept in greenhouse conditions. After 60 d, fresh and dry weight, root number, and length of plantlets were recorded. A general and significant improvement in the growth parameters was observed in the treated plants. All microbial strains proved to be indolacetic acid (IAA) producers using the Salkowsky method. A positive relationship between root number and length, and amount of IAA was found. The overall results suggest that the microbial priming of tomato seed could be useful for advancing organic farming, sustainable agriculture, and environmental protection.