Plant secondary metabolites (PSM) are small molecules of organic compounds produced in plant metabolism that have various ecological functions, such as defense against pathogens, herbivores, and neighboring plants. They can also help to reduce abiotic stresses, such as drought, salinity, temperature, and UV. This chapter reviewed the ecological functions of the PSM and how people utilize these metabolites to reduce crop biotic and abiotic stresses in agriculture. Specific topics covered in this review are (1) extraction of PSM from plant parts and its application on crops; (2) screening of crop/cover crop germplasms for high PSM content and with resistance to pathogens, herbivores, and/or neighboring plants; (3) regulation of PSM biosynthesis (including plant hormones and defense activators) to increase plant readiness for defense; (4) transcriptome and genome technology improvements in the last decade leading to valuable tools to characterize differential gene expression and gene composition in a genome, and lineage-specific gene family expansion and contraction. In addition, there is a critical need to understand how the biosynthesis and release of allelochemicals occur. Filling this knowledge gap will help us to improve and encourage sustainable weed control practices in agriculture.
Part of the book: Secondary Metabolites
Cotton is the most critical fiber crop and one of the top three oilseed crops in the world. One pronounced feature of cotton is that it is rich in secondary metabolites, mainly including terpenoids, flavonoids, and phenolic acids. These secondary metabolites have various ecological roles, such as defense and signal transmission. With the concept of plant secondary metabolites becoming more and more evident in the mid-twentieth century, cotton secondary metabolites as natural phytoalexins were also established. Terpenoids are stored in pigment glands that are distributed almost all cotton plant surfaces or subsurfaces and defend cotton plants from chewing insects, pathogens, and other herbivores. Flavonoids are relevant to fiber quality and color and also play a role in mechanism in insect and pathogen resistance. Phenolic acids play a role in weed suppression and insect and pathogen resistance. There are several reviews on cotton secondary metabolites, and the most recent one was five years ago. They all focus on the metabolites themselves. None of them focus on applications in cotton production. This review started from browsing the abundant literature on cotton secondary metabolites, and then analyzing their potential application in cotton production. Finally, our recent findings were discussed in this chapter.
Part of the book: Best Crop Management and Processing Practices for Sustainable Cotton Production