Cotton {Gossypium spp.) fibers are produced primarily by G. hirsutum L., upland, and G. barbadense L., pima, or Extra Long Staple (ELS). Two ELS upland lines, developed by Texas AgriLife Research, along with 'FiberMax 832LL' (FM 832) and 'DPL Pima HTO' (Pima HTO), were grown in a randomized complete block design at College Station, TX, during 2007 and 2008. Subplots of spindle-harvested seedcotton were ginned on a saw gin or roller gin with appropriate lint cleaning. High-volume instrument (HVI) and Advanced Fiber Information System (AFIS) fiber parameters were determined. Combed 50-Ne (English yarn count) and 80-Ne yarns were produced. Upland ELS lines exhibited longer (p < 0.01) fibers than FM 832, but only TAM B182-33 ELS produced fibers longer or equal (p < 0.01) to Pima HTO. Upland ELS lines produced stronger 50-Ne ring-spun yarns than FM 832 but not Pima HTO, which also produced stronger 80-Ne ring-spun yarn than the upland ELS lines. While roller ginning resulted in significantly higher micronaire, longer upper half mean length, more uniform fiber lengths, and longer upper-quartile length than saw ginning among these genotypes, yarn parameters reported were not affected. All genotypes responded the same to ginning platform, suggesting that further development of the upland ELS trait will not dictate a change in ginning equipment for upland cotton. The upland ELS trait contributes to significantly improved upland yarn quality.

Extra‐long staple (ELS) pima cotton (Gossypium barbadense L.) in the United States is identified by fibers with an upper half mean length (UHML) of at least 34.9 mm. Upland cotton (Gossypium hirsutum L.) traditionally has been referred to as short or medium staple cotton and in 2008 comprised approximately 95% of U.S. production, with pima comprising about 5%. Upland cotton is grown on the majority of acreage devoted to cotton because of its yield potential relative to pima, and its fiber has been adequate for most end uses. However, cotton breeders have long sought to develop upland cotton with the elite fiber quality of pima. Nine upland cotton germplasm lines exhibiting the ELS trait have been developed and released by Texas A&M AgriLife Research. These lines are characterized by improved UHML and fiber bundle strength, average yield, and low lint percent. Improving lint yield potential and lint percent while maintaining the ELS trait in this upland cotton germplasm pool will depend on an understanding of the impact of the ELS trait on yield components. The objective of this study was to evaluate the impact of the upland ELS trait on within‐boll yield components when compared with two cultivars of upland cotton and one pima cotton cultivar.

Limited genetic diversity could be contributing to the limited genetic gains in upland cotton, Gossypium hirsutum L., fiber lengths and strengths. Smith and Coyle (1997) reported negative associations between many fiber quality traits and the number of fibers per unit surface area of seed (FSSA), the most basic lint yield component. The objective of this study was to determine if mutagenesis could be used to modify the associations of within‐boll yield components and fiber quality parameters. TAM 94L‐25 (Smith, 2003) (PI 631440) seeds were treated with 3% v/v ethyl methanesulfonate (EMS). Twelve TAM 94L‐25 M4:6 mutant (M) lines, ‘FiberMax FM 832’ (Constable et al., 2001) (PVP 9800258; PI 603955) and ‘Phytogen PSC 355’ (PI 612974), and the unmutated parent TAM 94L‐25 were grown in performance trials in 2008 and 2009. The data suggests EMS‐based mutagenesis was successful in producing variation for within‐boll yield characteristics as well as fiber quality. Whether or not linkages or pleiotropic effects were disrupted is equivocal, with some correlation values significantly different between the control cultivars and the M lines. Mutant lines M2, M3, M50, and M51 were identified with improved FSSA. Ethyl methanesulfonate–based mutagenesis could be a valuable additional tool to create selectable variation in cotton for basic lint yield components and to break linkages of basic yield components and fiber quality.

Cotton (Gossypium spp.) breeders must develop cultivars to meet the demand for longer, stronger, and more uniform fibers. In the current study, two cycles of divergent selection for fiber upper‐half mean length (UHML) and bundle strength (Str) were conducted within five diverse parental combinations selected based on their potential for the genetic improvement of fiber quality. Realized heritability estimates for UHML and Str were calculated for each cycle, and correlated responses among fiber properties and lint percent were measured as they responded to selection for UHML and Str. The results suggest that early‐generation selection for UHML and Str is an effective strategy for the genetic improvement of fiber quality at College Station, TX. Although UHML and Str were consistently negatively correlated with lint percent, the results demonstrate that sufficient variation for fiber quality exists within the Texas A&M AgriLife Research upland cotton germplasm to improve UHML and Str without a concomitant reduction in lint percent. A negative phenotypic correlation between UHML and fiber elongation at break was also observed and was independent of the association between Str and fiber elongation at break in multiple populations. These findings suggest that further investigation into the relationship between UHML and fiber elongation within the Texas A&M AgriLife Research germplasm is warranted.