The seven Pee Dee lines (PD 97006, PD 97019, PD 97021, PD 97047, PD 97072, PD 97100, and PD 97101) from the USDA/ARS, Florence, SC, were bred by O.L..
However, no SEs were observed in the Georgia or Pee Dee lines at this stage.
Among the Georgia and Pee Dee lines, the genotypes PD 97019, PD 97021, PD 97500, and GA 98033 were found to be embryogenic (Table 5).
The low percentage of seedlings in the Georgia and Pee Dee lines that produced SEs was not a surprise since extensive seed-to-seed variability in embryogenic capability was observed in almost all cotton cultivars tested, including Coker 352 when commercial seed lots were used (Trolinder and Xhixian 1989; Gawel and Robacker, 1990; Sakhanokho et al., 2001; Mishra et al., 2003).
Although the frequency of seedlings that gave rise to SEs was low within the regenerable Georgia and Pee Dee lines, the number of SEs produced from the regenerable plants was high for the two best embryogenic lines, PD 97019 and GA 98033.
The percentage of SEs that converted to plantlets for the other three regenerable Pee Dee lines was lower than for Coker 312 (Table 1).
On the other hand, this step took 4 wk or more for Pee Dee lines. Regenerated plantlets from these lines, though appearing as normal as those from Coker 312 and GA 98033 in Magenta jars, were very sensitive to ex vitro conditions.