Genetic variation in seed size in an introgression line population of Upland cotton

Authors: KANDEL, SAVYATA - New Mexico State University; Zeng, Linghe; DEVER, JANE - Clemson University; KELLY, CAROL - Texas A&M University; Whitelock, Derek; ZHANG, JINFA - Tennessee Technical University

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/30/2026
Publication Date: 6/3/2026
Citation: Kandel, S., Zeng, L., Dever, J., Kelly, C., Whitelock, D.P., Zhang, J. 2026. Genetic variation in seed size in an introgression line population of Upland cotton. Plants. 15(11). https://www.mdpi.com/2223-7747/15/11/1729.
DOI: https://doi.org/10.3390/plants15111729

Interpretive Summary: Upland cotton is widely grown for both its fiber and its seeds, which are used for oil and animal feed. One important trait in cotton is seed size, because larger, healthier seeds can improve germination, seedling growth, and even fiber production. However, upland cotton doesn’t naturally have much variation in seed size, which makes it hard for breeders to improve this trait through normal breeding. To overcome this challenge, researchers can bring in useful genes from Pima cotton, a related species with different seed characteristics. This study examined seed size in a large set of cotton introgression lines—plants that contain small portions of Pima DNA mixed into upland cotton. The goal was to understand how seed size varies and to identify seed sizes that might lead to stronger seedlings and better fiber yield. In 2022, about 1,600 of these lines were grown in New Mexico, and in 2023 additional field tests were done in New Mexico, Mississippi, and Texas. The results showed that both genetics and environment affected seed size. On average, acid-delinted seeds (seeds with the fuzz removed) weighed 9.58 grams per 100 seeds, while fuzzy seeds weighed 11.26 grams per 100 seeds. These sizes appear promising for improving seedling vigor and fiber yield. The study also found that seed size was not strongly linked to cottonseed oil content or fatty acid composition. This research lays the groundwork for future cotton varieties with bigger, stronger seeds, which can lead to better stands, more vigorous plants, and higher lint yield without hurting cottonseed oil value, directly benefiting U.S. cotton growers.

Technical Abstract: Upland cotton is an important fiber and oilseed crop. Cottonseed size, measured by seed index, is an important seed quality trait that affects seed germination, seedling vigor, fiber yield, and cottonseed nutrient content. However, genetic variation in cottonseed size is highly limited within upland cotton, limiting the genetic gain in cottonseed size. Introgression breeding can alleviate this bottleneck effect by introducing desirable genes from pima to upland cotton. This study was conducted to analyze the seed size from both fuzzy and acid-delinted seeds and to assess the appropriate cottonseed size. In 2022, a population of 1600 cotton introgression lines (ILs) was grown at Leyendecker Plant Science Center, NMSU, while three field tests were conducted in 2023, including NM with all the ILs and MS and TX each with 1000 ILs. The analysis of variance of seed size showed that genotypic and environmental variation were found in both types of seeds. The acid-delinted and fuzzy cottonseeds had a mean seed index of 9.58 g and 11.26 g, while the broad sense heritability was 0.56 and 0.32, respectively. Furthermore, the seed index was not significantly correlated with cottonseed oil and different fatty acids.