1 Introduction

The genus Gossypium, commonly known as cotton, encompasses approximately 50 species distributed across tropical and subtropical regions worldwide, excluding Europe. This genus is notable for its significant genetic diversity, which includes both diploid and allopolyploid species. The diploid species are primarily found in Africa and Asia, while the allopolyploid species are native to the Americas. The evolutionary history of Gossypium is marked by remarkable events such as transoceanic dispersal and hybridization, which have contributed to its extensive diversification. The genus originated around 5 to 10 million years ago, with rapid diversification into major genome groups shortly thereafter (Wendel et al., 2010; Viot and Wendel, 2023).

Studying the Gossypium genus is of paramount importance for several reasons. Firstly, it includes four domesticated species that are crucial for global cotton production: Gossypium hirsutum and Gossypium barbadense from the New World, and Gossypium arboreum and Gossypium herbaceum from the Old World (Wendel et al., 2010). These species have undergone significant genetic changes through domestication, making them valuable models for understanding plant evolution and domestication processes (Viot and Wendel, 2023). Additionally, the genus exhibits extraordinary morphological and cytogenetic diversity, providing insights into fundamental aspects of plant biology and the genomic basis of morphological traits. Understanding the evolutionary history and genetic architecture of Gossypium is also essential for cotton breeding and genetic improvement, as it can lead to the development of superior cotton varieties with enhanced fiber quality and stress resistance (Grover et al., 2018; Huang et al., 2020).

The objective of this study is to trace the evolutionary history of Gossypium, including the origins of diploid and allopolyploid species and the role of hybridization and transoceanic dispersal in their diversification, examine the domestication processes of the four cultivated species and their genetic and morphological transformations over time, explore the genomic architecture of Gossypium species, focusing on the genetic variations and structural changes that have contributed to their evolution and adaptation, and provide insights into the phylogenetic relationships within the genus and the implications for cotton breeding and genetic improvement. By achieving these objectives, this study will contribute to a deeper understanding of the Gossypium genus and its significance in both evolutionary biology and agricultural science.

2 Historical Overview of Gossypium Research

2.1 Early studies and discoveries

The genus Gossypium has been a subject of scientific inquiry for centuries, primarily due to its economic importance as a source of cotton fiber. Early taxonomic and evolutionary studies laid the groundwork for understanding the diversity within the genus, which includes over 50 species distributed across tropical and subtropical regions worldwide (Wendel et al., 2010). Initial research focused on the classification and geographic distribution of these species, revealing significant genetic diversity and the presence of both diploid and allopolyploid species (Wendel et al., 2010).

2.2 Milestones in gossypium research

Several key milestones have marked the progress of Gossypium research. The discovery of the allopolyploid nature of the New World cotton species, Gossypium hirsutum and Gossypium barbadense, was a significant breakthrough, highlighting the complex evolutionary history involving hybridization and polyploidization events (Hu et al., 2019). Phylogenetic studies using chloroplast DNA and nuclear ribosomal ITS sequences further refined the understanding of the relationships among Gossypium species, revealing the monophyletic nature of the genus and its biogeographic history. These studies also suggested that the genus originated in Africa, with subsequent long-distance dispersal events leading to the current distribution of species.

2.3 Advances in molecular biology and genomics

The advent of molecular biology and genomics has revolutionized Gossypium research. High-quality genome assemblies of key species such as Gossypium hirsutum, Gossypium barbadense, and Gossypium herbaceum have provided deep insights into the genetic and molecular bases of fiber quality, stress resilience, and evolutionary history (Hu et al., 2019; Huang et al., 2020). Comparative genomic analyses have elucidated the speciation processes and structural variations that underpin the diversity within the genus (Hu et al., 2019; Huang et al., 2020). These advances have not only enhanced the understanding of Gossypium evolution but also facilitated the development of improved cotton varieties through targeted breeding programs (Hu et al., 2019; Huang et al., 2020).

The historical overview of Gossypium research highlights a journey from early taxonomic studies to sophisticated genomic analyses, each phase contributing to a comprehensive understanding of the origin, evolution, and diversification of this economically vital genus.

3 Phylogenetic Classification of Gossypium

3.1 Current taxonomy and classification

The genus Gossypium encompasses over 50 recognized species distributed across arid and semi-arid regions of the tropics and subtropics. This genus includes both diploid and allopolyploid species, with significant morphological and genetic diversity. The four domesticated species, Gossypium hirsutum and Gossypium barbadense (New World allopolyploids), and Gossypium arboreum and Gossypium herbaceum (Old World diploids), are of particular agronomic importance (Wendel et al., 2010). The genus is divided into eight diploid genome groups (A, B, C, D, E, F, G, K) and a single allotetraploid clade (AD) (Chen et al., 2016). Recent genomic studies have provided deeper insights into the evolutionary history and relationships among these groups, highlighting the complex processes of transoceanic dispersal and hybridization that have shaped the current taxonomy (Huang et al., 2020).

3.2 Molecular phylogenetics

Molecular phylogenetic studies have significantly advanced our understanding of the evolutionary relationships within Gossypium. Analyses of chloroplast DNA (cpDNA) and nuclear DNA have revealed the phylogenetic structure of the genus, supporting the resolution of the eight diploid genome groups into six major clades (Chen et al., 2016). Comparative analysis of 19 Gossypium chloroplast genomes has shown that nucleotide distances in non-coding regions are about three times those in coding regions, with smaller distances within genome groups compared to those among them (Chen et al., 2016). Phylogenetic topologies based on nucleotide and indel data have provided robust support for the classification of these clades (Chen et al., 2016). Additionally, the use of character-state weighted parsimony analysis of cpDNA restriction site data has provided insights into the biogeographic history of the genus, indicating multiple long-distance dispersal events and subsequent radiations.

3.3 Evolutionary relationships within Gossypium

The evolutionary history of Gossypium is marked by significant events of long-distance dispersal and hybridization. The genus is believed to have originated in either Africa, with subsequent dispersal events leading to the current distribution of species. The divergence of the major diploid clades is driven by intercontinental dispersal. The allopolyploid species, which include the economically important Gossypium hirsutum and Gossypium barbadense, are thought to have arisen from a trans-Pacific transfer of an ancestral A-genome taxon to the Pacific coast of Mesoamerica or South America, followed by hybridization with an indigenous D-genome diploid. Recent genomic studies have further elucidated the phylogenetic relationships among the A-genomes, suggesting that all existing A-genomes may have originated from a common ancestor, and allotetraploid formation was shown to have preceded the speciation of A1 and A2. Both A-genomes evolved independently, with no ancestor-progeny relationship (Figure 1) (Huang et al., 2020; Viot and Wendel, 2023). These findings provide valuable insights into the complex evolutionary dynamics that have shaped the diversity within the Gossypium genus.

Figure 1 The evolution of the allotetraploid cotton genome (Adopted from Huang et al., 2020) Image caption: a, Inferred phylogenetic analysis among Gossypium and other eudicot plants. b, Summary of phylogenetic analysis with the approximately unbiased test in 10-kb windows. c, Distribution of Ks values for orthologous genes among cotton genomes. Peak values for each comparison are indicated in the parentheses. d, Comparisons of identical sites in orthologous genes. Violin plots summarize the distribution of identical sites. The center line in each box indicates the median, and the box limits indicate the upper and lower quartiles of divergence (n=20 types of synonymous mutation). P values were derived with Student’s t-test. e, Phylogenetic and ancestral allele analysis based on SNPs. The red, blue and green triangles represent the collapsed 21 A2 accessions, 14 A1 accessions and 30 (AD)1 accessions, respectively. The percentage value indicates the percentage of ancestral alleles for each species that were identical to those of the D5-genome. f, Number of nucleotide variations in A1 or A2 compared with At1 across the chromosomes. g, A model for the formation of allotetraploid cotton showing fiber phenotypes from the (AD)1 (accession TM-1), the D5, the A1 (var. africanum) and the A2 (cv. Shixiya1). Scale bar, 5 mm. h, A schematic map of the evolution of cotton genomes. Major evolutionary events are shown in dashed boxes (Adopted from Huang et al., 2020)

The figure drawn by Huang et al. (2020) illustrates the evolution of the allotetraploid cotton genome, with key insights into the phylogenetic relationships, genomic variations, and structural evolution among Gossypium species. This comprehensive genomic analysis provides a deep understanding of cotton evolution, highlighting the interplay between genetic diversity and adaptation.

4 Geographical Origin and Distribution

4.1 Centers of origin

The genus Gossypium is believed to have originated approximately 5 to 10 million years ago, with a rapid diversification into major genome groups shortly thereafter. The centers of origin for the domesticated species of Gossypium are divided between the Old World and the New World. The Old World centers include Africa and Asia, where the diploid species Gossypium herbaceum and Gossypium arboreum were domesticated. In contrast, the New World centers include the Americas, where the allopolyploid species Gossypium hirsutum and Gossypium barbadense were independently domesticated (Viot and Wendel, 2023).

4.2 Dispersal and migration patterns

The dispersal and migration patterns of Gossypium species are characterized by both transoceanic long-distance dispersal and regional migrations. The transoceanic dispersal is particularly notable in the formation of allopolyploid cottons, which arose from the hybridization of an A-genome species from Africa-Asia with a D-genome species from the Americas. This event likely occurred within the last 1 to 2 million years. Additionally, the New World diploid cottons underwent rapid diversification in the mid-Pleistocene, with multiple long-distance dispersals to regions such as Arizona, the Galapagos Islands, and Peru (Grover et al., 2018). Grover et al. (2018) revisited the molecular evolutionary processes and phylogeny in the geographically widely dispersed New World diploid cottons (Gossypium, subg. Houzingenia) (Figure 2), found that the species relationships are largely congruent with the most recent phylogenetic inferences for the subgenus using nuclear genes.

Figure 2 Nuclear phylogeny of Houzingenia without (left) and including (right) the introgressed accession of Gossypium aridum from the Mexican state of Colima (Adopted from Grover et al., 2018) Image caption: Divergence times are visualized on an ultrametric tree (left) whose colors correspond to the relative growth (blue) or reduction (red) of genome size in Houzingenia, as compared with the outgroup Gossypium longicalyx (Longiloba). Inferred ancestral genome sizes are displayed on a proportional tree (right) whose colors correspond to the degree of change within Houzingenia alone (Adopted from Grover et al., 2018)

4.3 Distribution of wild and cultivated species

The distribution of wild and cultivated Gossypium species is extensive, covering arid to semi-arid regions of the tropics and subtropics worldwide (Zhu et al., 2012). Wild species exhibit a disjunct population structure, often with small and isolated geographic ranges, suggesting relict populations from an ancient pantropic distribution. For instance, the D-genome species are found along the Pacific Coast of America, while the C-genome species are primarily located in Australia. The cultivated species, on the other hand, have a broader distribution due to human agricultural practices. Gossypium herbaceum and Gossypium arboreum have spread across Africa and Asia, reaching as far as Indonesia. Similarly, Gossypium hirsutum and Gossypium barbadense have been widely cultivated in the Americas and have become globally significant cotton crops (Viot and Wendel, 2023).

It can be seen that the genus Gossypium exhibits a complex pattern of geographical origin, dispersal, and distribution, driven by both natural evolutionary processes and human agricultural activities. The centers of origin in Africa-Asia and the Americas, coupled with transoceanic dispersal and regional migrations, have contributed to the extensive diversity and distribution of both wild and cultivated Gossypium species.

5 Domestication and Evolutionary Diversification

5.1 History of cotton domestication

The domestication of cotton, particularly within the Gossypium genus, is a complex process that has occurred independently multiple times across different regions and species. The genus Gossypium includes approximately 50 species distributed globally, with four species independently domesticated for their fiber: two diploids from Africa-Asia and two allotetraploids from the Americas (Grover et al., 2021; Viot and Wendel, 2023). The domestication of Gossypium hirsutum and Gossypium barbadense, the two most commercially important species, began around 8,000 years ago in Mesoamerica and 5,500 years ago in South America, respectively. These species were transformed from wild perennial shrubs into annual crops with improved fiber qualities through human selection (Viot and Wendel, 2023).

5.2 Genetic changes during domestication

The domestication process has led to significant genetic changes in cotton species. Comparative genomic analyses have revealed that species-specific alterations in gene expression, structural variations, and expanded gene families were responsible for the speciation and evolutionary history of Gossypium hirsutum and Gossypium barbadense (Wang et al., 2018; Hu et al., 2019). The cultivated tetraploid cotton genotypes have clustered into distinct clades, indicating a clear genetic differentiation from their wild ancestors (Zhou et al., 2022). Selection pressure analysis has shown that wild species experienced greater natural selection, while cultivated genotypes underwent artificial selection, leading to reduced nucleotide diversity in cultivated varieties compared to their wild counterparts (Grover et al., 2021; Zhou et al., 2022). Introgression and gene flow between cultivated and wild species have also played a role in shaping the genetic landscape of modern cotton varieties (Fang et al., 2017; Zhou et al., 2022).

5.3 Diversification of cultivated varieties

The diversification of cultivated cotton varieties has been driven by both natural and artificial selection. The allotetraploid cotton species, Gossypium hirsutum and Gossypium barbadense, have undergone extensive structural variations and introgression events, contributing to their genetic diversity and adaptation to different environments (Wang et al., 2018). The introgression of favorable traits from Gossypium barbadense into Gossypium hirsutum has been particularly significant in improving fiber quality (Wang et al., 2018). Wang et al. (2018) conducted a study on the molecular mechanism of the development extra-long fibers in Gossypium barbadense, and measured dynamic changes in the elongating fibers of TM-1 and Hai7124 plants from 5 to 40 DPA (Figure 3). Additionally, the independent domestication events and subsequent interspecific hybridization have led to a rich genetic pool, allowing for the development of varieties with diverse morphological and agronomic traits (Viot and Wendel, 2023). This genetic diversity is crucial for ongoing breeding programs aimed at enhancing fiber quality, disease resistance, and environmental resilience in cotton crops (Fang et al., 2017; Wang et al., 2018; Hu et al., 2019).

Figure 3 Model showing the molecular mechanism responsible for development of longer fibers in Gossypium barbadense (Adopted from Wang et al., 2018) Image caption: a, Phenotypes of fiber-bearing seeds in Hai7124 and TM-1 plants. Numbers above the graphs are DPA. Scale bar, 10 mm. b, Fiber elongation patterns for TM-1 and Hai7124. Each value is the mean ± s.d. of fiber length for at least ten seeds from three individual plants at a given time point. c–e, Comparison of the content of the main osmotically active solutes soluble sugar (c), malate (d) and K+ (e) between TM-1 and Hai7124 fibers. DW, dry weight. f, Transmission electron microscopy (TEM) analysis of epidermal cell structure in 5-DPA ovule, showing the large central vacuole in the fiber cell compared with fiber base and epidermal cell. Scale bars, 10 µm in the figure and 100 nm in the inset. PD, plasmodesmata; C, cytosol; V, vacuole; CW, cell wall. g, Model depicting the roles of open PD and the genes related to the main osmotically active solutes in fiber elongation. Suc, sucrose; M, malate; Fru, fructose; Glu, glucose. h–k, qRT–PCR analysis of TST1 (h), VIN1 (i), ALMT16 (j) and NHX1 (k) in fibers from TM-1 plants at 5–25 DPA and from Hai7124 plants at 5–30 DPA. Each value represents the mean ± s.e.m. **P < 0.01, Student’s t test. The expression of TST1, VIN1, NHX1 and ALMT16 in fibers from TM-1 plants at 30 DPA is not shown because RNA could not be extracted from fibers at this time point (Adopted from Wang et al., 2018)

In summary, the domestication and evolutionary diversification of the Gossypium genus have been shaped by a combination of independent domestication events, genetic changes during domestication, and the diversification of cultivated varieties through natural and artificial selection. These processes have resulted in the development of cotton species with improved fiber qualities and adaptability, making them economically important crops worldwide.

6 Genetic and Genomic Studies

6.1 Genome sequencing efforts

Genome sequencing efforts in the Gossypium genus have significantly advanced our understanding of cotton's genetic architecture and evolutionary history. High-quality de novo-assembled genomes for Gossypium barbadense and Gossypium hirsutum have provided insights into the origin and evolution of allotetraploid cotton. These efforts revealed species-specific alterations in gene expression, structural variations, and expanded gene families responsible for speciation and evolutionary history (Hu et al., 2019). Additionally, the assembly of the first Gossypium herbaceum genome and improvements to the Gossypium arboreum and Gossypium hirsutum genomes have elucidated the phylogenetic relationships and origin history of cotton A-genomes, highlighting the independent evolution of A-genomes without an ancestor-progeny relationship (Huang et al., 2020).

6.2 Comparative genomics

Comparative genomics has been instrumental in unraveling the consequences of both ancient and recent polyploidy in Gossypium. By comparing genetic maps of extant diploid and tetraploid cottons, researchers inferred the approximate order of loci along the chromosomes of their hypothetical common ancestor. This approach revealed significant correspondence in gene arrangements between Gossypium and Arabidopsis, despite the complexities introduced by polyploidy and gene loss (Rong et al., 2005). Whole-genome comparative analyses of Gossypium barbadense and Gossypium hirsutum have further elucidated the evolutionary history of these species, identifying key structural variations and gene family expansions that contributed to their speciation and domestication (Hu et al., 2019).

6.3 Key genetic markers and traits

The identification and mapping of key genetic markers have provided valuable insights into the genome organization, transmission, and evolution of cotton. Genetic maps for diploid and tetraploid Gossypium genomes, composed of sequence-tagged sites (STS), have revealed features such as negative crossover interference and locus duplication patterns. These maps have also identified SSRs, CAPS, and SNPs, which are crucial for marker-assisted improvement of cotton. Furthermore, the differential amplification of transposable elements has been shown to be responsible for genome size variation in Gossypium, with specific retrotransposon families proliferating in different lineages, contributing to genome size changes and evolutionary dynamics (Hawkins et al., 2006).

7 Ecological and Environmental Adaptations

7.1 Adaptations to various climatic conditions

The genus Gossypium, encompassing over 50 species, exhibits remarkable adaptability to a wide range of climatic conditions. This adaptability is evident in the distribution of Gossypium species across arid to semi-arid regions of the tropics and subtropics. The evolutionary history of Gossypium has been shaped by long-distance dispersal and hybridization, which have facilitated the genus's ability to thrive in diverse environments (Wendel et al., 2010; Wendel and Grover, 2015). The domesticated species, such as Gossypium hirsutum and Gossypium barbadense, have been particularly successful in adapting to various climatic conditions, contributing to their widespread cultivation and genetic diversity (Wendel et al., 2010).

7.2 Ecological interactions and symbioses

Gossypium species engage in various ecological interactions and symbioses that enhance their survival and reproduction. These interactions include relationships with pollinators, herbivores, and other plant species. The morphological diversity within the genus, ranging from herbaceous perennials to tall trees, supports a wide array of ecological niches and interactions (Wendel and Grover, 2015). The repeated domestication of different wild progenitors for seed fiber production also highlights the role of human-mediated ecological interactions in the evolutionary trajectory of Gossypium (Wendel and Grover, 2015).

7.3 Impact of environmental stressors

Environmental stressors, such as drought, salinity, and temperature extremes, have significantly influenced the evolution and diversification of Gossypium. The genus's ability to withstand these stressors is a testament to its genetic and cytogenetic diversity. The genomic diversity within Gossypium, including the presence of eight distinct genome groups, has provided a robust foundation for adaptation to various environmental challenges (Wendel and Grover, 2015). The allopolyploid species, in particular, have demonstrated resilience to environmental stressors, which has been a key factor in their agricultural importance and global distribution (Wendel et al., 2010; Wendel and Grover, 2015).

8 Biotechnological Advances and Applications

8.1 Genetic engineering in Gossypium

Genetic engineering has played a pivotal role in advancing the Gossypium genus, particularly in enhancing fiber quality and resilience to environmental stress. High-quality de novo–assembled genomes of Gossypium hirsutum and Gossypium barbadense have provided significant insights into the genetic and molecular bases for interspecies divergences, which are crucial for genetic engineering efforts aimed at improving fiber quality and environmental resilience (Hu et al., 2019). Additionally, the assembly of the Gossypium herbaceum genome and improvements in the Gossypium arboreum and Gossypium hirsutum genomes have provided valuable genomic resources that facilitate genetic modifications aimed at enhancing fiber cell properties (Huang et al., 2020).

8.2 Improvements in crop yield and quality

Biotechnological advancements have significantly contributed to improvements in crop yield and fiber quality in Gossypium species. The evolutionary history and domestication of Gossypium, particularly the American allopolyploid species, have been elucidated through comprehensive studies integrating taxonomic, biogeographic, molecular genetic, and phylogenetic data. These insights have been instrumental in understanding the genomic architecture of Gossypium and have paved the way for targeted breeding programs aimed at enhancing crop yield and fiber quality (Viot and Wendel, 2023). Furthermore, the repeated polyploidization events in Gossypium have led to the emergence of superior fiber productivity and quality in tetraploid cottons compared to their diploid counterparts, highlighting the potential for biotechnological interventions to further enhance these traits (Paterson et al., 2012).

8.3 Resistance to pests and diseases

The development of resistance to pests and diseases in Gossypium species has been a major focus of biotechnological research. The MIC-3 gene family, unique to Gossypium species, has been identified as a key player in root-knot nematode resistance. Molecular evolutionary studies of the MIC-3 gene family have revealed that these genes are evolving through a birth-and-death process, with strong positive selection pressure on certain exons, which may contribute to increased resistance to diverse pests and pathogens (Buriev et al., 2011). This understanding of the genetic basis for pest and disease resistance is crucial for developing genetically engineered Gossypium varieties with enhanced resistance traits.

9 Future Directions and Research Prospects

9.1 Emerging trends in Gossypium research

The study of the Gossypium genus is rapidly evolving, with several emerging trends promising to advance our understanding of its origin and evolutionary diversification. High-throughput sequencing technologies have revolutionized genomic research, enabling the assembly of high-quality reference genomes for various Gossypium species. These advancements facilitate comprehensive comparative genomics studies, revealing insights into polyploidy, gene flow, and speciation processes.

Another significant trend is the application of CRISPR-Cas9 and other genome editing tools. These technologies allow precise manipulation of cotton genomes, paving the way for functional genomics studies that can elucidate gene functions and regulatory networks. Additionally, the integration of multi-omics approaches, including transcriptomics, proteomics, and metabolomics, is providing a holistic view of the molecular mechanisms underlying important agronomic traits (Nicora et al., 2020).

Advances in bioinformatics and computational biology are also driving Gossypium research. Machine learning algorithms and artificial intelligence are being employed to analyze complex genomic data, predict gene functions, and identify candidate genes for breeding programs. Furthermore, the increasing availability of phenotyping platforms, such as remote sensing and high-throughput phenotyping, is enhancing our ability to link genotype to phenotype, thereby improving trait selection and breeding efficiency.

9.2 Potential areas for further study

Several areas warrant further investigation to fully exploit the genetic potential of Gossypium species. One promising area is the study of polyploidy and its role in the evolution of spinnable cotton fibers. The repeated polyploidization events in Gossypium have led to significant genetic complexity, which may hold the key to understanding fiber quality and productivity (Paterson et al., 2012). Another critical area is the exploration of the genomic basis of morphological diversity within the genus. With over 50 species exhibiting a wide range of reproductive and vegetative characteristics, there is a wealth of genetic diversity that remains untapped. Additionally, the construction of introgression lines to introduce favorable chromosome segments from Gossypium barbadense to Gossypium hirsutum offers a practical approach to identify loci associated with superior fiber quality, which can be leveraged in breeding programs (Wang et al., 2018).

9.3 Implications for cotton breeding and agriculture

The insights gained from recent genomic studies have profound implications for cotton breeding and agriculture. Understanding the genetic and molecular bases for interspecies divergences in Gossypium can inform breeding strategies aimed at improving fiber quality and resilience to environmental stress (Hu et al., 2019). The identification of quantitative trait loci associated with fiber quality through introgression line populations provides a direct pathway to enhance cotton breeding programs (Wang et al., 2018). Furthermore, the elucidation of the evolutionary history and domestication processes of Gossypium species offers a framework for utilizing genetic resources more effectively, guiding the development of cotton varieties that are better adapted to changing environmental conditions (Viot and Wendel, 2023). These advancements not only benefit cotton production but also contribute to the broader field of plant biology by providing a model for studying polyploidy and its evolutionary consequences.

10 Concluding Remarks

The genus Gossypium, commonly known as cotton, encompasses approximately 50 species distributed across tropical and subtropical regions worldwide, excluding Europe. The evolutionary history of Gossypium is marked by significant events such as transoceanic dispersal, hybridization, and polyploid formation. These processes have led to the diversification of the genus into eight major genome groups (A through G, and K). Notably, the genus includes four domesticated species: the New World allopolyploids Gossypium hirsutum and Gossypium barbadense, and the Old World diploids Gossypium arboreum and Gossypium herbaceum.

The domestication of Gossypium hirsutum and Gossypium barbadense in the Americas occurred independently, with archaeological evidence suggesting origins dating back 8,000 and 5,500 years, respectively. This dual domestication was followed by interspecific introgression, further contributing to the genetic diversity observed in modern cotton species. Molecular genetic studies have revealed ancient hybridization events and cryptic intergenomic introgression, particularly involving Gossypium gossypioides and its relationship with other D-genome species.

The research on the origin and evolutionary diversification of the Gossypium genus has significantly advanced our understanding of plant evolution, domestication, and genetic diversity. Comprehensive taxonomic investigations have clarified the classification and relationships among Gossypium species, providing a robust framework for further studies. Advances in genome sequencing have elucidated the phylogenetic relationships and evolutionary history of cotton genomes, particularly the A-genomes and their role in polyploid formation. The parallel domestication events in the Americas have highlighted the complex interplay between human selection and natural evolutionary processes, offering insights into the domestication of other crop species. Additionally, studies on interspecific hybridization and introgression have revealed the dynamic nature of Gossypium evolution, emphasizing the importance of genetic exchange in shaping the diversity of the genus.

The study of the Gossypium genus has provided a comprehensive understanding of its evolutionary history, domestication, and genetic diversity. Future research should focus on expanded genomic studies, including continued efforts in genome sequencing and comparative genomics to provide deeper insights into the evolutionary mechanisms and genetic basis of important traits in Gossypium species. Conservation of genetic diversity, both in wild and domesticated Gossypium species, is crucial for maintaining the resilience and adaptability of cotton crops in the face of environmental changes. Additionally, functional genomics research, investigating the roles of specific genes and genomic regions, will aid in developing improved cotton varieties with enhanced fiber quality, disease resistance, and stress tolerance. Integrating data from archaeology, molecular genetics, and biogeography will offer a holistic understanding of the evolutionary history and domestication of Gossypium, facilitating the application of this knowledge in crop improvement programs.

By addressing these areas, researchers can continue to unravel the complexities of Gossypium evolution and leverage this knowledge to enhance the sustainability and productivity of cotton agriculture.

Acknowledgments

The CropSci Publisher thanks the two anonymous peer reviewers for their thorough evaluation of the manuscript and their valuable suggestions and recommendations for improvement.

Conflict of Interest Disclosure

The author affirms that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.

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