Phage Therapy: Application in Plant Disease Control

Bacteriophages, or phages, are viruses that specifically infect bacteria. Phages have predominantly been used in medical and veterinary applications, but they have recently gained attention for controlling plant diseases. The use of phages in the biological control of plant pathogens stems from their ability to kill bacteria and their presence in bacterial environments. This indicates their ability to survive in the host's domain. Phages have been utilized in integrated disease management programs due to their ease of use, compatibility with other bactericides, alternative pesticide use, and relatively low cost. Despite doubts regarding the effective use of bacteriophages as biocontrol agents, the emergence of antibiotic-resistant bacteria and concerns about the transfer of antibiotic resistance from plant pathogens to human pathogens, as well as the occurrence of copper-tolerant strains among plant bacteria, have increased the inclination to use bacteriophages in modern agriculture. So far, phage therapy has been successfully employed against pathogens such as Pseudomonas tolasi, bacterial leaf spot of beans, soft rots caused by Pectobacterium species, fire blight in apple and pear (Erwinia amylovora), potato scab (Streptomyces scabies), bacterial blight of geranium (Xanthomonas hortorum pv. pelargonii), and bacterial spot of tomato (Xanthomonas campestris pv. vesicatoria). Bacteria can indeed develop resistance to phages through mechanisms similar to those observed with antibiotics. Still, the advantage of phages over antibiotics in treating pathogens lies in their ability to induce genetic mutations and infect new hosts. The major challenge in phage-based biocontrol is translating successful laboratory experiments into effective field control methods against pathogens. Therefore, a comprehensive understanding of the ecology and complex host–phage interactions in different plant environments is necessary to achieve desirable phage utilization as a biocontrol method. This chapter attempts to provide an overview of the potential of bacteriophages in the biological control of plant pathogens and introduce their advantages and challenges.