Genomic and cytogenetic analysis of synthetic polyploids between diploid and tetraploid cotton (Gossypium) species

Authors: KHIDIROV, MUKHAMMAD - Uzbekistan Academy Of Sciences; ERNAZAROVA, DILRABO - Uzbekistan Academy Of Sciences; RAFIEVA, FERUZA - Uzbekistan Academy Of Sciences; ERNAZAROVA, ZIRAATKHAN - Uzbekistan Academy Of Sciences; TOSHPULATOV, ABDULQAHHOR - Uzbekistan Academy Of Sciences; UMAROV, RAMZIDDIN - Uzbekistan Academy Of Sciences; KHOLOVA, MADINA - Uzbekistan Academy Of Sciences; Udall, Joshua - Josh; Yu, John; KUSHANOV, FAKHRIDDIN - Uzbekistan Academy Of Sciences; ORIPAVO, BARNO - Uzbekistan Academy Of Sciences; KUDRATOVA, MUKHILSA - Uzbekistan Academy Of Sciences; GAPPAROV, BUNYOD - Uzbekistan Academy Of Sciences; KHIDIROVA, MAFTUNAKHAN - Uzbekistan Academy Of Sciences; KOMILOV, DONIYOR - Uzbekistan Academy Of Sciences; TURAEV, OZOD - Uzbekistan Academy Of Sciences

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/2023
Publication Date: 12/17/2023
Citation: Khidirov, M., Ernazarova, D., Rafieva, F., Ernazarova, Z., Toshpulatov, A., Umarov, R., Kholova, M., Udall, J.A., Yu, J., Kushanov, F., Oripavo, B., Kudratova, M., Gapparov, B., Khidirova, M., Komilov, D.N., Turaev, O. 2023. Genomic and cytogenetic analysis of synthetic polyploids between diploid and tetraploid cotton (Gossypium) species. Plants. 12(24). Article 4184. https://doi.org/10.3390/plants12244184.
DOI: https://doi.org/10.3390/plants12244184

Interpretive Summary: The cotton genus has many wild species that are potentially valuable sources of genetic variation for cotton improvement. In recent years there have been declines in genetic advances for fiber yield and quality as well as biotic and abiotic stress tolerance in upland cotton. Tapping into rich genetic resources of the cotton genus becomes relevant, but introgression of desirable traits from the wild species into cultivated cottons is tedious, hindering the progress of exploiting wild cotton germplasm. In this study, we made several crosses between African diploid cotton (G. herbaceum) and Brazilian tetraploid cotton (G. mustelinum) accessions, known for their adaptation to adverse environments, to produce triploid F1 hybrids that were unstable and sterile. Upon colchicine treatment and segregant analysis, we identified allohexaploid F1 hybrids that were stable and fertile. Genomic and cytogenetic changes were observed in the segregating synthetic hybrids at different polyploidy levels. Transgressive cotton plants with long fiber and extra-long fiber were identified in the treated F2 progeny. Morphological, cytological, and genomic variation in the synthetic hybrids were analyzed. Synthetic allotetraploid cottons would serve as valuable sources in the introgression of important traits including biotic and abiotic stress tolerance into the elite upland cotton varieties.

Technical Abstract: Cotton (Gossypium spp.) is the most important natural fiber source in the world. The genetic potential of cotton can be successfully and efficiently exploited by identifying and solving the complex fundamental problems of systematics, evolution, and phylogeny, based on interspecific hybridization of cotton. This study describes the results of interspecific hybridization of G. her-baceum L. ('1-genome) and G. mustelinum Miers ex Watt ('D4-genome) species, obtaining fertile hybrids through synthetic polyploidization of otherwise sterile triploid forms with colchicine (C22H25NO6) treatment. The fertile F1C hybrids were produced from five different cross combi-nations: 1) G. herbaceum subsp. frutescens × G. mustelinum; 2) G. herbaceum subsp. pseudoarboreum × G. mustelinum; 3) G. herbaceum subsp. pseudoarboreum f. harga × G. mustelinum; 4) G. herbaceum subsp. africanum × G. mustelinum; 5) G. herbaceum subsp. euherbaceum (variety '-833) × G. mustelinum. Cytogenetic analysis discovered normal conjugation of bivalent chromosomes in addition to univalent, open, and closed ring-shaped quadrivalent chromosomes at the stage of metaphase I in the F1C and F2C hybrids. The setting of hybrid bolls obtained from these crosses ranged from 13.8-92.2%, the fertility of seeds in hybrid bolls from 9.7-16.3%, and the pollen viability rates from 36.6-63.8%. Two transgressive plants with long fiber of 35.1-37.0 mm and one plant with extra-long fiber of 39.1-41.0 mm were identified in the F2C progeny of G. herbaceum subsp. frutescens × G. mustelinum cross. Phylogenetic analysis with 72 SSR markers that detect genomic changes showed that tetraploid hybrids derived from the G. herbaceum × G. mustelinum were closer to the species G. mustelinum. The G. herbaceum subsp. frutescens was closer to the cultivated form, and its subsp. af-ricanum was closer to the wild form. New knowledge of the interspecific hybridization and synthetic polyploidization was developed for understanding the genetic mechanisms of the evolution of tetraploid cotton during speciation. The synthetic polyploids of cotton obtained in this study would provide beneficial genes for developing new cotton varieties of the G. hirsutum species, with high-quality cotton fiber and strong tolerance to biotic or abiotic stress.