In this special issue, we highlight the role of phytohormones and emerging PGRs in the regulation of plant defense responses. Pathogenic microbes are responsible for enormous crop loss during pre and post-harvest storage conditions and, thus, are one of the major threats to sustainable crop production. The final outcome of a defense response is determined by the type and extent of activated immunity which is governed by the genetic potential of the hosts and an interplay of various classical phytohormones and emerging plant growth regulators (PGRs).

Photo credit: Symptoms of a plant pathogen and causal agent of oat and barley crown rust - Puccinia coronate on oat leaves - Telium, plural telia. By Tomasz Klejdysz in Shutterstock.