**1. Introduction**

Cotton is the world's most important natural fiber crop and one of the top oilseed crops among soybean, rapeseed, canola, sunflower seed, and peanut. Another byproduct is the protein-rich meal from cotton seeds. Cotton is grown in 75 countries worldwide [1]. Different from other crops, cultivated cotton includes four species in the genus *Gossypium*: *G. hursutum*, *G. barbadense*, *G. arboretum*, and *G. herbaceum*. The first two are allotetraploid and distributed in the New World (Americas), and the latter are diploid and distributed in the Old World (Asia and Africa). The genus *Gossypium* belongs to the *Malvaceae* family, and it has approximately 50 diploid species among eight genomes (A–G and K genomes) and seven allotetraploid species [2, 3].

Beyond its economic value, cotton also possesses a rich array of secondary metabolites and organic compounds synthesized by plants for various ecological functions.

These secondary metabolites play a crucial role in the plant's defense against pests, pathogens, and environmental stresses. There are at least three reviews on cotton secondary metabolites: [4–6]. Ref. [4] is comprehensive and expected the cotton secondary metabolites to be utilized to defend against pests in cotton production, but data accumulation was not as abundant as in the present day, and that was published before GMO cotton appearance; Ref. [5] focused more on cotton terpenoids; and Ref. [6] focused on cotton flavonoids. This review will follow the coverage of Ref. [4] and review the logical development of the utilization of secondary metabolites in cotton production.

In recent years, there has been a growing interest in harnessing the potential of cotton secondary metabolites for applications in agronomy. Part of the reason is that cotton is still the "dirtiest" crop as it consumes 10.24% of the insecticides and 4.71% of pesticides in 2019 with only 2.5% of the arable land according to the International Cotton Advisory Committee [7], and it was one of the early crops that widely adopted GMO technology [8].

The key distinction between the eras of Refs. [4, 5], and the current period lies in the acknowledgment of secondary metabolites in plants as an innovative foundation for potential biopesticides. This recognition has opened avenues for their application in sustainable agriculture, as highlighted by Ref. [9]. Researchers and agronomists have identified the diverse properties of secondary metabolites, including antimicrobial, insecticidal, antioxidant, and allelopathic activities. These bioactive compounds have the potential to revolutionize agricultural practices by offering environmentally friendly alternatives to synthetic pesticides, fertilizers, and growth regulators.

The use of cotton secondary metabolites in agronomy presents several advantages. Firstly, it provides an opportunity to reduce the reliance on conventional chemical inputs, thereby minimizing the environmental impact of their use. Secondly, these natural compounds may offer a sustainable solution to combat pests while maintaining crop productivity. Moreover, using cotton secondary metabolites can lead to the development of novel bio-based products and promote the concept of integrated pest management (IPM) and sustainable agriculture.

This review explores the current knowledge and research advancements in using cotton secondary metabolites in agronomy. It will delve into the compounds' chemical diversity, modes of action, and potential applications in crop protection, nutrient management, and plant growth promotion. Furthermore, the challenges and opportunities associated with their practical implementation will be discussed, along with future perspectives for utilizing cotton secondary metabolites in sustainable agricultural systems.

By critically evaluating the existing literature and highlighting key findings, this review intends to provide a comprehensive overview of the potential benefits and limitations of incorporating cotton secondary metabolites into agronomic practices. Ultimately, such insights can contribute to developing innovative strategies that harness the power of these bioactive compounds to promote sustainable and environmentally conscious approaches to crop production.
