A simple method of crossing commercial cultivars with PD germplasm lines and simultaneously selecting for high yield potential and extra-fiber strength was adequate for producing 11 superior selections. We crossed five Southeastern and midsouth cultivars with 19 current and nine obsolete PD cultivars and germplasm lines. Individual F₃ plants and F₄ rows were field selected for seed cotton yield. These selections were also evaluated in the laboratory for lint percentage, fiber length, fiber strength and micronaire. Superior selections were first compared for yield potential and fiber and spinning properties with check cultivars at Florence, South Carolina in 1986. Tests with selections from each cross consisted of a randomized complete block design with four replications. Second year tests of 11 superior lines were conducted at Tifton, Ga., Jay, Fla., and Blackville and Florence, S. C. Cultural practices followed state recommendations for maximum lint production.

Comparison of selections from crosses with current and obsolete PD germplasms support previous reports that genetic linkages between lint yield and fiber strength have been broken in current PD germplasm and this is an excellent source of extra-fiber strength genes for use in cotton improvement programs.

We developed superior selections from crosses with DES 422, Delcot 311, Deltapine 41, McNair 220, and McNair 235. DES 422, McNair 220, and McNair 235 have PD germplasm in their ancestry; however, they do not carry genes for extra-fiber strength. Delcot 311 has triple-hybrid germplasm in its ancestry and Deltapine 41 has extra-fiber strength when compared with most midsouth cultivars which may account for the excellent compatibility with the PO germplasm.

Additional crosses of seven Chinese cultivars with three current and five obsolete PD cultivars and germplasm lines produced no selections comparable with PD-1 or PD-3 using similar breeding procedures. Although selections produced excellent seed cotton yields, problems with low lint percentage, short fibers, coarse fibers, and inadequate fiber strength were encountered. More complex breeding methods will be required for cotton improvement in crosses between PD germplasm and highly diverse upland cottons.