Divergent Selection in Gossypium for Fiber Length and Strength

Low genetic diversity among elite upland cotton (Gossypium hirsutum) cultivars is a challenge concerning the genetic improvement of fiber quality. Two cycles of divergent selection for fiber upper-half mean length (UHML) and bundle strength (Str) were conducted within five populations derived from the following four genetically diverse parental lines: ‘Tamcot 22’ (G. hirsutum), 06 WE 62-4 (G. hirsutum), TAM B182-33 ELSU (G. hirsutum), and 04 SID 84-2 (G. hirsutum x G. barbadense). Realized heritability estimates for UHML and Str were calculated for each cycle. Phenotypic correlations among HVI fiber properties and lint percent (LP) as they responded to selection for UHML and Str were determined across and within parental combinations. The results demonstrate that there is abundant genetic variation regarding UHML and Str among the parental combinations, and early generation selection for UHML and Str was an effective strategy for the genetic improvement of fiber quality within four of the five populations at College Station, TX. There were consistent negative correlations between fiber properties and LP. However, several strains with simultaneously improved HVI fiber quality and LP were identified within each population, providing evidence of repulsion phase linkage. A subset of these lines resulting from divergent selection have also been characterized by AFIS fiber analysis and yarn quality analysis. The effect of selection for UHML and Str on the correlations among AFIS fiber properties and yarn properties will be discussed.