Abstract
Horticultural crops have important economic value in the world. Biotic stress has serious impacts on horticultural crops' growth and development as well as yield. Melatonin, a multifunctional signaling molecule, has been increasingly documented to play a pivotal role in mediating plant defense responses against diverse biotic stressors, including bacterial, fungal, and viral pathogens in horticultural crop species. Previous studies showed that exogenous melatonin treatment significantly improved horticultural crops growth and increased their tolerance to biotic stress. Although there are numerous studies to show that exogenous melatonin treatment can markedly improve the tolerance for horticultural crops in response to biotic stress, the role of melatonin in biotic stress responses remains unclear and requires clarification. In the review, we summarize the effects of melatonin on horticultural crops' disease resistance. Moreover, we assess future perspectives in melatonin research and its applications to improve horticultural crop production and tolerance for biotic stress. This review explores future research directions and potential applications to enhance the productivity and biotic stress tolerance of horticultural crops, and also provides a theoretical basis for enhancing the scientific understanding of the role of melatonin in response to biotic stress in horticultural crops.