Bio-osmopriming tomato (Lycopersicon esculentum Mill.) seeds for improved seedling establishment

Bio-osmopriming (BOP) is a combination of osmoconditioning and biopriming procedures that simultaneously hydrates seeds and applies a bacterial coating. The bacterium applied is Pseudomonas aureofaciens AB254. Processing tomato (cv. 'OH 8245') seedlots of 5 g each received one of four treatments; untreated, osmoprimed, AB254 coated, and bio-osmoprimed. Osmoprimed treatments soaked the seeds in aerated -0.8 MPa NaNO3 for 7 days and then dried them back to their original moisture content (approx. 14%). Seeds were bio-osmoprimed by soaking in aerated -0.8 MPa NaNO3 for 4 days at which time a mixture of nutrient broth, polyalkylene glycol, and bacterial stock were added. Seeds were then hydrated for an additional 3 days. In the absence of pathogen pressure, no differences in germination were observed between BOP and conventional osmopriming. Bio-osmopriming treatments consistently contained 10(5) bacteria colony forming units (cfu) per seed compared to 10(8) cfu for AB254 coated treatments. When seeds were planted in soilless media infected with Pythium ultimum, AB254 coatings protected tomato seeds from infection equally as well as the fungicide metalaxyl. Bio-osmopriming also provided protection, but at a slightly lower rate. This technique improves the chances of the seed lot establishing a healthy stand.