ABSTRACT

The genetic mapping of economically important quantitative traits in cotton is hindered by the lack of suitable genetic populations for analysis. A Hybrid Cotton project at New Mexico has been devoted to deriving Gossypium hirsutum breeding lines that exhibit varying amounts of introgression from G. barbadense. A core set of 25 near-homozygous lines have been identified that have exhibited stable breeding behavior during many generations of maintenance. In 1991 and 1992, 24 "species-specific" morphological plant characteristics were scored in the field at Las Cruces. Based on composite morphological scores the breeding lines displayed a continuum of morphology from G. hirsutum-like to G. barbadense-like. The most interesting lines are those that exhibit an "intermediate-phenotype", which is rare in typical interspecific populations. These progenies are being screened for Random Amplified Polymorphic DNA (RAPD) markers to determine phylogenetic relationships at the molecular level. The genotype that clusters intermediate between typical G. hirsutum and G. barbadense will be selected to initiate genetic mapping populations, by hybridization to a typical G. hirsutum. RAPD methodology has been optimized for this material and random decamer primers are being screened for their ability to detect polymorphisms. Ultimately, molecular markers will be developed that can facilitate interspecific introgression or tag fiber quality traits derived from past introgression events.