Genetic analysis of the Asiatic cotton (Gossypium arboreum) petal spot phenotypes

Authors: Erpelding, John

Submitted to: Plant Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/12/2021
Publication Date: 12/14/2021
Citation: Erpelding, J.E. 2021. Genetic analysis of the Asiatic cotton (Gossypium arboreum) petal spot phenotypes. Plant Breeding. 141(1):71-76. https://doi.org/10.1111/pbr.12984.
DOI: https://doi.org/10.1111/pbr.12984

Interpretive Summary: Flower characteristics have been used to evaluated cotton varieties that are conserved by the United States Department Agriculture, National Plant Germplasm System and these traits are useful as visible markers when transferring genes between different cotton species. Most of the Asiatic cotton varieties (Gossypium arboreum) available in the germplasm collection have a red-colored spot at the base of each flower petal and these spots are referred to as petal spots. A few varieties do not produce petal spots and are described as spotless. There are also a few varieties that have a non-colored region at the base of the petal that appears as a white spot, which has been termed ghost spots. The Asiatic cotton variety PI 615742 with the ghost spot trait was identified from the germplasm collection and crossed with variety PI 452097, having red petal spots, and with variety PI 529708 that was spotless. Populations were developed from the two crosses to determine the number of genes controlling the petal spot trait. More than 200 plants in each population were evaluated for petal spots and these data indicate two independent genes controlled the development of petal spots. One gene determined whether the petal spot was present or absent with the presence of petal spots the dominant trait. The other gene was responsible for pigmentation of the spot and red petal spots were the dominant trait. Variety PI 452097 has the dominant gene for the presence of petal spots, but is recessive for the pigment gene resulting in ghost spots. Both genes were recessive for variety PI 529708 resulting in the lack of petal spots. For variety PI 452097, the two genes were dominant leading to the development of red petal spots. Results of this study can be used in future research to evaluate how the two genes interact to control pigmentation of cells in a specific region of the flower petal.

Technical Abstract: The cotton species Gossypium arboreum L. is self-pollinated and most accessions in the United States Department Agriculture, National Plant Germplasm System produce flowers with red pigmented petal spots, which was considered the primitive phenotype and more attractive to pollinators. Few accessions have the ghost spot phenotype and genetic analysis of this trait was conducted for PI 615742. Two F2 populations were developed by crossing PI 615742 with G. arboreum accessions PI 452097, having red petal spots, and with PI 529708, showing the spotless phenotype. The PI 615742 × PI 529708 population data indicate a single completely dominant gene confers the ghost spot phenotype. Petal spot phenotypes observed for the PI 615742 × PI 452097 population indicate red pigmented spots are also conferred by a single completely dominant gene. These results support a two gene model in which the presence of petal spots and pigment development are controlled by independent genes. The accessions and population data can aid in characterizing the mechanisms controlling floral traits and cell specific pigment expression.