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

Bio-osmopriming is a combination of osmoconditioning and biopriming procedures that simultaneously hydrates seeds and applies a bacterial coating in a single treatment. The bacterium applied is Pseudomonas aureofaciens AB254. Processing tomato (cv. 'OH 8245') subsamples (5 g each) from a single seedlot received one of 4 treatments; untreated, osmoprimed, AB254 bioprimed, 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. The seeds were then hydrated for an additional 3 days. In the absence of pathogen pressure, no differences in germination were observed between bio-osmopriming and conventional osmopriming. Bio-osmoprimed treatments consistently contained 10(5) bacteria colony forming units (cfu)/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 seedlot establishing a healthy stand.