dc.description.abstract | 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. | en |