Molecular Variation Among and Within Improved Cultivars in the U.S. Cotton Germplasm Collection
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abstract
Many cotton (Gossypium spp.) accessions conserved in the U.S. Cotton Germplasm Collection are not characterized sufficiently to encourage breeders' interest in using these accessions. This study was conducted to determine the genetic variability of several groups of improved Gossypium hirsutum L. accessions and how this variability can be used to enhance current breeding programs. These groups were selected based on region or era of development and included cultivars from China and northern and southern Africa and obsolete and recent U.S. cultivars. Both inter-and intracultivar diversity were observed among these cultivars, but larger patterns of diversity based on region or era of development were poor or lacking. Heterozygosity levels averaged 44% for all groups, with Chinese cultivars showing the lowest polymorphism (72%) and polymorphism information content (PIC) values (0.332). The African cultivars showed the highest levels of intracultivar molecular variation with 13.4% polymorphic loci. The majority of molecular diversity was found within groups (62.2%) and within cultivars (31.0%) rather than among groups (6.8%). The average genetic similarity between cultivars was 0.832, ranging from 0.675 to 0.999. This information will provide cotton breeders with more accurate guidance in the selection of unique and desirable accessions to introduce diversity that possibly will reduce vulnerability to disease and insect pressures and could provide improvements for yield, agronomic, and fiber quality traits. Crop Science Society of America.
