The use of the polymerase chain reaction (PCR) to generate random-amplified polymorphic DNA (RAPD) markers was applied to an interspecific population segregating for fiber quality traits. A cross was made between Gossypium hirsutum acc. TM-1 and G. barbadense acc. 3-79, which both are genetic and cytogenetic standards for their respective species (Kohel, 1973). TM-1 is a long-term inbred derived from Deltapine 14. 3-79 is originated from doubled haploid Pima cottons before any known introgression with G. hirsutum occurred and possesses extra long staple qualities associated with many G. barbadense selections. 127 individual (TM-1 X 3-79)F₂ plants were maintained in the greenhouse to serve as a resource for DNA sampling, verification of phenotypic traits, and a fiber source for fiber strength determination.

Fiber samples collected from individual F₂ plants were analyzed by stelometer to measure bundle fiber strength of each of the individual plants. Measurements were also obtained for length, uniformity and elongation. The bundle fiber strength (cN/tex) of F₂ individuals ranged from 17 to 34.6 (r²=0.96). The bundle fiber strength associated with segregating RAPD markers within the sampled plants also had a similar distribution. The variations in fiber strength represented a normal distribution between the extreme measurements for bundle fiber strength in parental TM-1 (20.2±0.4) and 3-79 (30.2±0.8) parents (20 replications).The F(2 ) plants were scored for five segregating phenotypic characters of G. hirsutum TM-1 (p(1)r²lc(1)l(2)_oy(1)) and G. barbadense 3-79 (P(1)R²Lc(1)L(2)_oY(1)). Genetic segregation appeared to fit that expected for a single gene inherited trait (X(2)(3:1) 0.36-1.84). F₃ plants were evaluated to verify scored homo/heterozygous plants. To establish chromosome anchor positions within the cotton genome for quality trait analysis and to identify linkages of the RAPD markers, the RAPDs were screened against a collection of interspecific F₁ monosomic and monotelodisomic cotton lines. The cottons were F₁ plants of monosomic or monotelodisomic plants in a TM-1 background crossed with 3-79 (Stelly, 1993). Sixty-four RAPD markers, for which polymorphism between the two parent lines was observed were screened to identify chromosomes associated with the markers. Preliminary screens were conducted on interspecific F₁ monosomic lines, representing 14 of the 26 cotton chromosomes (n=2X=26). Thirty monotelodisomic F₁ plants aided identification of RAPD markers with other chromosomes, and with short or long arm chromosome assignments. Twenty-five RAPD fragments, of TM-1 origin, were anchored to 16 of the 26 chromosomes.

These anchored RAPD markers, when screened on the interspecific F₂ population were useful to study the inheritance of fiber strength, and other fiber quality traits. Over 500 polymorphic RAPD markers, distinguishing between TM-1 and 3-79, have been identified and some of them appear linked to the fiber strength trait. Efforts are continuing to map these quality trait associated markers. Likewise, these markers are also being compared with available mapped RFLP markers (Reinisch et al, 1994) to help confirm assignments. Using the available polymorphic interspecific F₂ population, molecular DNA markers, and quality traits measurements we hope to locate genes involved with the complex traits associated with cotton fiber quality.