| dc.description.abstract | Soybean [Glycine max (L.) Merr.] breeders need to use the most efficient and
inexpensive method to advance populations during the inbreeding process. Most breeders
in the soybean industry prefer the bulk method because it requires less hand labor during
harvest. This study used molecular markers to compare the single seed descent (SSD), the
single-pod descent (SPD) and the bulk methods. The objective was to identify the most
efficient method of inbreeding by determining which method had the greatest number of
unique lines and the fewest pairs of redundant lines. The number of pairs of redundant
lines was detem1ined by scoring each of 100 F 4 5 lines, developed from each of the three
inbreeding methods, using 21 polymorphic SSR markers. A similarity coefficient (Sxv)
was used to determine the level of similarity between each possible pair of lines within
each inbreeding method. The SSD method was used as a control to identify the number of
lines that were identical by descent for the SPD and bulk methods. Unique lines were
lines that were not paired with any other line within that inbreeding method for the
specified level of genetic similarity. At the Sxy =::: 0.875 level of genetic similarity, 49% of
the lines were unique for the SSD, 44% of the lines were unique for the SPD, and 39% of
the lines were unique for the bulk method, but the difference in the number of unique
lines among methods was not significant. For the SSD method, zero lines were identical
by descent with another line. For the SPD method, at the Sxy? 0.875, there were 16 pairs
oflines that were identical by descent. For the bulk method, at the Sxy? 0.875, there were
42 pairs of lines that were identical by descent. This result was evidence that due to genetic sampling, there were more redundant lines for the bulk method and SPD than for
the SSD method. The number of unique lines developed by each of the three inbreeding
methods is the most important measure of the relative efficiency of each method.
However, there was no significant difference in the number of unique lines among these
methods. Therefore, the most efficient method should be the method that requires the
least time and labor during harvest. The SSD method requires too much time during
harvest to be practical for a commercial soybean breeder. The decision as to whether to
use the SPD or bulk method will depend on which of those two methods is the most
practical for that specific breeding program. | en_US |
