Comparison of the single seed descent method (SSD), the multiple seed descent method (MSD) and the bulk population method for yield and protein improvement in wheat

The bulk population (BP), multiple seed descent (MSD), and single seed descent (SSD) methods were compared in a cross to determine their relative effectiveness in a yield and protein improvement program. F4 BP, F6 SSD, and F6 MSD lines were seeded in 81-entry 5 m single row plots in a triple lattice experiment and 12-entry randomized completed block trials, respectively, with the cultivars Glenlea and Benito as check varieties. Breeding methods did not influence mean grain yield or grain protein, but ranges in grain yield and grain protein, as well as phenotypic variances, were greater for the MSD lines than in lines derived by either the SSD or BP method. The top 20 percent of the best-performing lines, whose yields were closest to mean grain yield of the check variety Glenlea, were mostly lines derived by the MSD method, followed by the ones derived through the BP method. With respect to the mean grain protein, the lines that came closest to the check variety Benito were the ones derived by the MSD method, while the SSD and BP methods were equally effective in providing high protein lines (lines having a protein level equal to or higher than Benito). A direct comparison of 36 BP lines with their corresponding 36 SSD lines and top ranking 36 MSD sister lines (lines originating from the same F2 single plant) indicated that 52.7 percent of the MSD lines were high yielding compared to only 5.6 percent and 16.7 percent for the SSD and BP lines, respectively. For grain protein, 52.8 percent of the MSD sib lines had mean grain protein equal to or higher than the mean grain protein of Benito compared to 50 percent and 41.7 percent for the SSD and BP lines respectively. The proportion of corresponding lines that combined both high yield and high protein was 19.4 percent for the MSD lines, and 2.8 percent of the BP lines, respectively. The MSD method was superior to the SSD and BP methods in breeding for high yield alone and it also provided the greatest number of lines which combined both high yield and high protein content