Gene Flow between Gossypium hirsutum L. and Gossypium barbadense L. is Asymmetric
- Allen E. Van Deynze *a,
- Robert B. Hutmacherb and
- Kent J. Bradforda
- a Seed Biotechnology Center, One Shields Ave., Univ. of California, Davis, CA 95616
b Dep. of Plant Sciences, Univ. of California, Davis, CA and Shafter Research and Extension Center, Shafter, CA, 93263. This research was funded by a grant from the California Crop Improvement Association and by Cotton Incorporated, 6399 Weston Parkway, Cary, North Carolina 27513
As both Pima cotton (Gossypium barbadense L.) and Acala (Upland; G. hirsutum L.) are grown in the southwestern United States, understanding gene flow within and among these species is important to maintain genetic purity. In small scale and commercial fields, gene flow decreased exponentially from 1.44% at 1 m to less than 0.50% at 10 m in Acala cotton. Corresponding values for Pima cotton were 0.19% at 3 m and 0% at 10 m or beyond. When interspecies outcrossing occurred, Pima cotton was preferentially pollinated by Acala cotton. Gene flow was nondetectable in 7.5 m borders. Asymmetric pollination between Acala and Pima cotton was also observed in samples collected in borders located 6 m from the pollen source with no detectable gene flow beyond 7.5 m. At a given distance, in commercial scale Pima fields, gene flow was tenfold less than reported in Acala fields with gene flow not exceeding 0.43% beyond 10 m. No gene flow was detected beyond 800 m (0.5 mile). This study indicates that isolation distances can be shorter in Pima cotton than in Acala cotton to maintain the same level of genetic purity. Comparison with historical evidence suggests that there has been a shift in the relative gene flow among species in modern cultivars of Pima cotton.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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