Genetic and Molecular Mechanisms and Approaches for Improving Cotton Fiber Quality for Sustainable Agriculture

Cotton (Gossypium hirsutum L.) is an economically important fiber crop whose quality determines textile processing efficiency, yarn performance, fabric durability, and market value. Cotton fiber quality is a complex quantitative characteristic influenced by genetic architecture, molecular regulatory networks, physiological processes, and environmental conditions. This review provides a comprehensive overview of the fundamental properties of cotton fiber, developmental processes, genetic inheritance, and molecular mechanisms underlying fiber quality. Major fiber attributes, including length, strength, uniformity, fineness, and elongation, are examined in relation to fiber initiation, elongation, secondary cell wall formation, and maturation. The genetic architecture of fiber quality is discussed through genetic variability, heritability, quantitative trait loci (QTLs), linkage mapping, genome-wide association studies (GWAS), and genotype-by-environment interactions. Particular attention is given to molecular mechanisms regulating fiber development, including transcription factors, hormonal signaling, carbohydrate metabolism, cellulose biosynthesis, and cell-wall remodeling. Furthermore, advances in cotton genomics, transcriptomics, epigenomics, proteomics, metabolomics, and functional genomics are explored to demonstrate their contributions to candidate-gene identification and functional validation. Emerging breeding technologies, including marker-assisted selection, genomic selection, CRISPR/Cas-mediated genome editing, genetic engineering, and regulatory RNA molecules, offer promising opportunities for improving fiber characteristics. Nevertheless, challenges remain in validating molecular discoveries across diverse genetic backgrounds and environmental conditions, managing genetic diversity, and translating laboratory findings into consistent field performance. Climate change and associated abiotic stresses further emphasize the need to develop cultivars that combine superior fiber quality, high productivity, and environmental resilience. Integrating multi-omics information, high-throughput phenotyping, precision breeding, and multi-environment evaluation could accelerate the development of improved cotton cultivars. Overall, this review highlights the importance of connecting fundamental fiber biology with advanced molecular technologies and conventional breeding to achieve sustainable genetic improvement and maintain cotton quality under changing agricultural conditions. Integrating conventional breeding, molecular markers, genomic selection, and genome editing offers promising opportunities to improve cotton fiber quality sustainably. These approaches can accelerate the development of climate-resilient cultivars with enhanced fiber properties, resource-use efficiency, genetic diversity, and long-term agricultural productivity.