Abstract:

It provides important and necessary information for future soybean breeding to estimate the genetic contribution from the end ancestors of the released cultivars. Based on the pedigree data of 1 300 soybean cultivars released during 1923−2005 in China, the nuclear and cytoplasmic contribution rates of the end ancestors to each of the cultivars were calculated and analyzed. The 1 300 cultivars were traced back to 670 nuclear and 344 cytoplasmic ancestors and had 45.44% (49.77%), 23.23% (26.31%), 7.33% (9.62%), 4.40% (4.62%), 0.87% (1.08%), and 0.55% (0.77%) of nuclear (cytoplasmic) germplasm from Eco-region I, II, III, IV, V, VI, 17.75% (7.00%) from foreign countries, and 0.45% (0.85%) from geographic-unknown sources, respectively, while the nuclear (cytoplasmic) germplasm of the cultivars mainly came from their own eco-regions released them. During the last decade (1996−2005), among 592 cultivars released, their nuclear (cytoplasmic) germpasm from foreign countries, eco-region VI and some geographic-unknown sources increased by 11.96% (8.85%), 0.89% (1.07%), and 0.22% (0.62%), but those from eco-region I−V decreased by 7.83% (4.22%), 3.66% (6.13%), 0.66% (0.34%), 0.64% (0.41%), and 0.27% (0.12%), respectively; 46 core end ancestors of the cultivars released during 1996−2005 were nominated on the basis of their nuclear and cytoplasmic contribution; the exchange and utilization of germplasm among eco-regions were improved but mostly still limited in their own eco-regions. Therefore, it is necessary to strengthen germplasm exchange among eco-regions for broadening genetic bases of the future cultivars.

Key words:

Soybean, Germplasm constitution, Geographic source, End ancestor, Genetic contribution