Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2005
Publication Date: 9/23/2005
Citation: Zhang, J.F., Lu, Y., Adragna, H., Hughs, S.E. 2005. Genetic improvement of New Mexico acala cotton germplasm and their genetic diversity. Crop Science. 45:2363-2373. Interpretive Summary: New Mexico has a history of breeding Acala 1517 cotton varieties. The breeding first started in 1926 and has continued to the present day. Each generation of Acala 1517 cottons has shown quality improvement in one or more factors up until recent times. A project was started in 2003 to quantify quality gain over the approximately 75 year breeding program and to evaluate strategies for quality gains in the future. Future selections will concentrate on increasing boll number per plant, partially by breeding for increased heat tolerence and increased resistance to verticillium wilt. Future selections will also focus on increasing the number of fibers that occur per seed. This project has shown that exisiting Acala 1517 germplasm still contains significant genetic diversity to accomplish the above goals in the future.
Technical Abstract: The New Mexico cotton breeding program was established in 1926 and has been led by five generations of breeders and geneticists. The program has released more than 30 Acala 1517 cotton cultivars and numerous germplasm lines known for high fiber quality and Verticillium wilt tolerance that have made substantial contributions to cotton breeding in the U.S. The present project was initiated in 2003 to evaluate the genetic improvement of Acala 1517 cultivars and lines released over the past 75 years in yield, boll size, seed index, lint percentage, fiber length, fiber strength, and micronaire. Their genetic divergence was also estimated using simple sequence repeat (SSR) markers. Based on the data available from annual yield trials, lint yield and lint percentage in Acala 1517 cotton have steadily increased since the 1930, while boll size and seed index have gradually decreased since the 1960s. Fiber strength has been enhanced since the 1960s, which has been accompanied by steady increase in micronaire. However, fiber length in Acala 1517 cultivars tended to shorten from 31.0 to 30.0 mm from 1960 to 1990, whereas newly released Acala 1517 cultivars (Acala 1517-95, 1517-99, 1517-02, 1517-03, and 1517-04) have fiber greater than 30.5 mm. Genetic distance among Acala 1517 genotypes ranged from 0.06 to 0.38 with an average of 0.18 based on 189 SSR marker alleles, indicating a substantial genetic diversity among Acala 1517 cotton germplasm. Divergent germplasm introgression in the program has contributed to genetic diversity of Acala cotton germplasm and continuous genetic gain in Acala cotton cultivar improvement.