Osmoprotectants Improve Shelf-life and Efficacy of Desiccation-tolerant Pseudomonas Strains for Biological Control of Fusarium Dry Rot
Date & Time
Monday, July 18, 2022, 2:00 PM
Patricia Slininger

When produced as a triculture of desiccation-tolerant Pseudomonas sp. dried onto Kenite, this biological control agent (BCA) has been shown to significantly reduce Fusarium dry rot decay of stored potatoes in laboratory and small pilot trials. Extending dry shelf-life is desirable to improve BCA consistency and economics. In prior studies osmoprotective sugars—isomelezitose, trehalose, and fructose—prolonged the storage life of dried formulations of native Pseudomonas strains which were desiccation-sensitive. In the current study, the same three buffered osmoprotectants and a control without sugar were applied to nine desiccation-tolerant isolates—three evolved from each of the triculture parent strains—to determine if dried shelf-life could be further extended. A one-microliter droplet of each treatment was spotted per each of 10 wells of a 96-well microplate, and replicated microplates were air dried 1 h at ambient temperature and then vacuum-packed and stored at 25 C to hasten degradation. At regular time intervals over 3 months storage, replica microplates were reconstituted and the BCA assessed with respect to cell survival, cell reactivation rate, and dry rot disease reduction in potato wounds co-inoculated with BCA and conidia of the pathogen, Fusarium sambucinum. Significant main and interactive effects of osmoprotectants with isolates and storage time were observed, and benefits were evident. After 3 months storage, trehalose most consistently improved performance of all strain lines of the BCA triculture by reducing viable cell losses by 2-4 orders of magnitude, reducing cell doubling recovery time by 13-27 h, and boosting dry rot disease reduction by 24-41%; both fructose and isomelezitose showed promise for some of the desiccation-tolerant isolates but were not consistently beneficial to all strain lines. Although trehalose is on the market, isolmelezitose may offer a future option for osmoprotection if its production is commercialized using recently discovered glucansucrase technology.

Session Type
Parent Session
7/18 - Concurrent Sessions B