Encapsulated Predatory Bacteria Efficiently Protect Potato Tubers from Soft Rot Disease

Soft rot Pectobacteriaceae (SRP) are a group of destructive Gram-negative phytopathogens that can infect a wide range of plant hosts, including potatoes. There are no effective control agents available against SRP, making their management challenging. We have developed a novel approach to protect potato tubers against SRP. It makes use of encapsulated predatory Bdellovibrio bacteriovorus bacteria that, upon release from a polymeric carrier, prey upon SRP. We applied a carrageenan-trehalose-based formulation containing a B. bacteriovorus HD100 predator to prevent soft rot disease development in potato tubers, under various conditions. The dried formulation exhibited very high stability over an 18-month period at room temperature (~25°C), in contrast to unencapsulated suspensions of the predator, in which viability decreased rapidly below detection level. The rehydrated formulation was as efficient as freshly grown unencapsulated predators and provided high protection in potted potato tubers, displaying an average of 50% reduction in disease parameters (e.g., tissue decay and disease index) under controlled conditions at 7 days postinoculation and planting. The protective effect provided by this formulation was maintained in longer-term trials (28 days) conducted in larger vessels within a net house under natural climate conditions, highlighting its potential for practical application in the field.