Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/2/2003
Publication Date: 12/1/2003
Citation: Bowman, D.T., Gutierrez, O.A. 2003. Sources of fiber strength in the U.S. cotton crop from 1980-2000. Journal of Cotton Science. 7:164-169. Interpretive Summary: Recently cotton breeders have been criticized for lack of progress in improving cotton cultivars. This has been primarily directed in the area of lint yield. The basis for the criticism has been the lackluster yields in recent years. Genetic uniformity is the named culprit for this situation, although that is debatable. One area that has shown marked improvement in the U.S. cotton crop during the 1980's and 1990's is fiber strength. Only from 1995 to 2000 did fiber strength decline. The objective of this study was to determine the genetic source of fiber strength improvements and decline during the course of this study. First, the successful cultivars, those that occupied at least 1% of cotton hectarage, were determined using statistics from the USDA, Agricultural Marketing Service for 1980-2000. Second, pedigrees of successful cultivars were examined. Third, fiber data furnished by the USDA from the Regional Cotton Variety Testing Program were analyzed. The Acalas were a source of high strength fiber genes accounting for one half of the improvement. Genes also came from the USDA, ARS Pee Dee Program and accounted for 12.5% of the improvement. This second source can truly be labeled an exotic source of a diverse source since their high-strength fiber genes did not originate from an Upland source. Another 25% of the improvement in fiber strength was the result of transgressive segregation, i.e. a unique combination of the same genes. The decline in fiber strength from 1995 to 2000 was the direct result of seed companies using parents in their transgenic breeding programs that had fiber strength lower than the average in 1995. If this practice continues then fiber strength will either be stagnant or decline further.
Technical Abstract: The U.S. cotton (Gossypium hirsutum L.) crop has shown remarkable improvements in fiber strength until the late 1990's. At the same time concerns about the lack of genetic diversity have been raised. The objective of this study was to discern the source of improved fiber strength and decline during the 1980's and 1990's. Using data from the USDA, Agricultural Marketing Service on area planted to commercial cultivars, pedigree information, and fiber data of the USDA, ARS Regional Cotton Variety Testing Program, we discerned the most popular cultivars, their pedigrees, and their fiber strength. The source of fiber strength genes were determined by examining pedigrees. The Acalas, particularly from New Mexico State University, accounted for half of the fiber strength improvement. Transgressive segregation played a role in 25% of the improvements while the USDA, ARS Pee Dee Program supplied 12.5% of the high fiber strength genes. The decline in fiber strength improvement from 1995 to 2000 was the result of the use of backcrossing to produce transgenic cultivars which accounted for the bulk of the hectarage in the latter part of the 1990's.