Strigolactones and Plant Defense

Biotic stress is a condition in which detrimental biological factors interact with plants and disrupt their normal growth. These biological factors include organisms like bacteria, fungi, viruses, insects, nematodes, and weeds. They drain nutrients from their host plant, affecting optimal growth and, in severe situations, causing the host plant to die. Biotic stress is a major threat that causes terrific losses in agriculture by affecting crop yield. The primary morphological symptoms of biotic stress are rotting, chlorosis, stunting, and the development of local lesions. In order to combat biotic stresses, plants have developed a wide range of complex defense mechanisms. It includes morphological, biochemical, and molecular adaptive mechanisms triggered by various plant hormonal signaling pathways. Strigolactones (SLs) are plant hormones that influence growth, development, and stress responses in plants. It has been found that SLs play a role in mediating plant defense responses to various biotic stresses. It is found to be involved in defending the host plants against attacks from pathogenic bacteria, fungi, nematodes, aphids, and pests, thus endowing stress tolerance in plants. SLs protect plants from pathogens and pests, primarily by preventing their growth, encouraging stomatal closure to reduce invader access, and increasing the production of hydrogen peroxide. SLs can crosstalk with other defense hormones to activate defense responses in plants. The main focus of this chapter is on SLs’ function in activating plant defense against pests and pathogens.