Trends in Phenotypic Diversity in Public Cotton Breeding Programs

The Regional Breeder Testing Network (RBTN) is the premier method for the testing and exchange of elite cotton germplasm within the public sector in the US. One of the stipulations associated with entry of germplasm lines in the test is that it is freely available for use in crossing. Historical evidence has been presented that there is a narrow genetic base in US cotton. Does continued use of material in the RBTN exacerbate the problem of a narrow base or is there a sufficient influx of new genetic variability? A phenotypic diversity analysis of the RBTN over time may be a useful proxy for an expanding/static/shrinking genetic base across public cotton breeding programs.