Abstract: The Pectobacterium and Dickeya pectinolytic bacteria are phytopathogens responsible for several macerating diseases on a wide range of crops and ornamental plants. Recently, bacterial predators belonging to the Bdellovibrio and like organisms (BALOs) were shown to efficiently prey on these rot-causing bacteria and reduce soft rot-induced potato slice maceration. In the current research, our novel approach aimed at developing and studying a κ-carrageenan-based encapsulation system for fast-release of entrapped B. bacteriovorus HD100 in high numbers to prevent bacterial soft-rot infections. κ-carrageenan-dried carriers swelled and dissolved upon immersion in water due to a loss of potassium ions which are the main cross-linking agents. Survival rates of the predators after drying were higher for immobilized bdelloplasts (e.g., predator inside the host) compared to attack phase (host-searching, AP) cells, and with the addition of the osmoprotectant trehalose to the carriers. Released encapsulated predators preyed efficiently on soft rot bacteria, with bdelloplasts performing better as compared to AP cells. However, predation dynamics were influenced by the type of added osmoprotectant. Carrageenan-trehalose carriers encapsulating predators were able to reduce soft-rot disease in situ using a potato slice assay. To our knowledge, this research is the first to explore the potential of encapsulated BALOs against phytopathogens. Key points: • Dissolution of the carriers was affected by potassium concentration in the system. • Encapsulation of bdelloplasts with trehalose best maintained the predator viability. • The encapsulated predators efficiently controlled soft rot in vitro and in situ.
Bibliographical noteFunding Information:
The authors thank for the financial support from Adama company and the Office of the Chief Scientist, Ministry of Agriculture and Rural Development, Israel. We would like specially to thank Limor Poraty, Noam Sheffer, Danny Karmon and Ofer Hochberg from Adama for their support. In addition, we would like to express our appreciation to Dr. Einat Zelinger from the Microscopy Unit at the Hebrew University of Jerusalem for performing the SEM imaging.
This research was supported by research grant 12–02-0044 from the Adama company and the Office of the Chief Scientist, Ministry of Agriculture and Rural Development, Israel.
© 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.