Selection for soybean lines having high seed protein

Soybean seeds from 738 introduced varieties were analyzed for protein percentage and 5 highest protein accessions were identified i.e., G7945, G8355, G8884, G8891 and G8976. They were hybridized to form single and double cross hybrids from which a pedigree selection was applied. The single cross group was selected for 4 consecutive generations while the double cross one was selected for 3 generations according to high protein as well as seed size greater than 10.5 grams per 100 seeds. In the last cycle of selection only plant setting over 200 seeds were chosen. Eight and 12 lines were kept from single cross and double cross groups, respectively. They were field-evaluated with their parental varieties and recommended cultivars. Selected lines from the single cross groups were found different in several traits, except for number of seeds per pod, 100 seed weight, days to 50 percent flowering and days to maturity. Selected lines from the double cross groups were more uniformed, except in protein percentage. Selection from double cross hybrids seemed to be more effective as they produced lines with over 23 percent more yield per rai with higher number of seeds and seed weight per plant, as compared to lines from the single cross hybrids. Average yield per rai of single cross and double cross lines were higher than those of the recommended cultivars by 26 percent and 64 percent while protein percentages were higher by 9 and 8 percent, respectively. However, 100 seed weight of the selected lines were lower than those of the recommended cultivars. Five selected lines were finally chosen as having protein content ranging from 50.4 to 52.7 percent, seed yield ranging from 290 to 533 kg/rai, protein yield from 146 to 271 kg/rai, oil content from 15.4 to 16.4 percent, oil yield per rai from 45 to 84 kg, and 100 seed weight over 11.3 gm. The selected lines expressed higher yield per rai, protein percentage, and protein per rai than the recommended cultivars. However, their oil percentage, oil yield per rai, and 100 seed weight were lower than those of the recommended cultivars.