Genetic improvement of fiber quality in tetraploid cotton: an overview of major QTLs and genes involved in and edited for the quality of cotton fibers

Abstract Cotton, an important industrial crop cultivated in more than 70 countries, plays a major role in the livelihood of millions of farmers and industrialists. Cotton is mainly grown for its fiber, an economic component that can be differentiated from its epidermal cells in the outer integument of a developing seed. Fiber length, fiber strength, and fiber fineness are three main attributes that contribute to the quality of cotton fibers. Recent advancements in genomics have identified key genes, which are the most important factors that govern these three traits, can be introduced into cultivars of interest via gene editing, marker-assisted selection, and transgenics, thus the narrow genetic background of cotton can be addressed and its fiber quality traits can be enhanced. Over the past two decades, quantitative trait loci (QTLs) have been mapped for different fiber traits, approximately 1 850 QTLs have been mapped for fiber length, fiber strength, and fineness among which a few genes have been edited for quality improvement in cotton. In this background, the current review covers the development and the factors that influence these traits, along with the reported genes, QTLs, and the edited genomes for trait improvement.