Inheritance of Cotton Fiber Length and Strength

The U.S. cotton industry has become predominantly an export market which requires a higher standard of fiber quality than does the domestic market. To remain competitive, U.S. cotton must meet the quality standards demanded by the consumers of raw cotton whether domestic or abroad. Diallel and generation means analyses (GMA) were conducted on fiber quality data of nine and five parental genotypes, respectively, to gain a better understanding of the genetic control of cotton fiber length and strength as well as to ascertain the value of the reported genotypes toward the improvement of fiber quality. Parental genotypes included extra-long staple uplands (Gossypium hirsutum, L.), EMS mutated uplands, high strength uplands, and interspecific hybrids.

General combining ability (GCA) and specific combining ability (SCA) were estimated according to Griffing?s diallel Model I, Method 4 for lint percent, high volume instrument (HVI) upper half mean length (UHML), fiber bundle strength (Str), uniformity index, elongation, micronaire, advanced fiber information system (AFIS) upper quartile length on a weight basis, mean length on a number basis, short fiber content on a number basis, immature fiber content, maturity ratio, and standard fineness. Estimates of GCA were significant across environments for all traits. SCA effects were significant for most traits but accounted for a smaller proportion of the variability in comparison to GCA effects. TAM B182-33 ELS would be the parent of choice to simultaneously improve fiber length and Str.

The GMA was conducted on the parental, F_(1), F_(2), and backcross generations. Low levels of transgressive segregation for both UHML and Str were observed for some populations. Broad sense heritability ranged from 0.00 to 0.67 for UHML and from 0.22 to 0.82 for Str. Additive gene action was significant for all but three parental combinations for UHML and for all parental combinations for Str. Generally, the significance and magnitude of additive genetic effects were more consistent among parental combinations and years than were non-additive genetic effects for both UHML and Str. Dominance and epistatic genetic effects often were of a greater magnitude than additive genetic effects but in an inconsistent manner, and in both positive and negative directions.