¹ Department of Plant and Soil Science, Alabama A&M University, Normal, AL 35762

² USDA/ARS, Crop Science Research Laboratory, PO Box 5367, Mississippi State, MS 39762

Due to the widespread use of high speed spinning technology in the yarn and textile industry, the demand for high strength fiber in raw cotton has increased. Improvement of cotton fiber quality through conventional breeding is limited because of the complexity of fiber quality genetics. Hence, the primary goal of this project was to identify and characterize genes related to cotton fiber quality. Messenger RNAs were isolated from the fiber layers of high yielding Upland cotton, TM-1, and high fiber quality Pima cotton, 3-79, respectively. A cDNA library was constructed from the high fiber-quality line, 3-79, and screened differentially with the cDNA probes obtained from mRNAs of TM-1 and 3-79, respectively. Thirteen cDNA clones were selected and subjected to Northern hybridization analysis. Five of the thirteen cDNAs showed high expression in the twenty day-post-anthesis (dpa) fiber tissue of 3-79 cotton. Sequence analysis indicated the presence of a cotton lipid transfer protein, a mitogen-activated protein kinase and a novel gene with no homologous sequences in the Genbank database. The remaining two separate cDNAs showed high identity in nucleotide sequence to 6-day G. arboreum and 7-10 dpa G. hirsutum fiber cDNAs, respectively, but of unknown functions. The cDNA clones differentially expressed in the 3-79 cotton fiber were presumed to be associated with cotton fiber quality, but their specific contribution had not been determined. These sequences represent one of the few reports to study fiber-associated gene expression in Pima cotton (G. barbadense).