Impacts of drought on plant disease development and use of biological control agents to mitigate its adverse effects

Drought and plant diseases are the most complex and deleterious stress factors that limit plant growth and have a negative effect on crop productivity. Such stresses are compounded by the impacts of climate change, which will predictably increase the frequency and duration of drought periods in the future, thus affecting the development and spread of plant diseases. Biological control is an ecologically friendly alternative for the management of drought-induced plant diseases as well as the improvement of crop production in drought-affected environments. The use of biological control agents (BCAs) can increase plant tolerance to both stresses, reduce the application of agrochemicals, minimize environmental risks, and promote sustainable agricultural production. This chapter focuses on understanding the responses of plants, soil microbial communities, and plant pathogens to drought stress and the interactive effects of simultaneous drought stress and pathogen infection on plants. The most important BCAs belonging to Bacillus, Pseudomonas, Streptomyces, Trichoderma, and arbuscular mycorrhizal fungi, as well as their modes of action, are discussed in light of their possible role in mitigating the adverse effects of drought on plant disease development. The paper analyzes the significance of BCAs for the growth and health of agricultural crops, followed by their limitations and prospects.