Breeding potential of the backcross progenies of a hybrid between <i>Trifolium medium</i> × <i>T. pratense</i> to <i>T. pratense</i>

Abstract

In this study, T. medium (zigzag clover, 2n = 80 and T. pratense (red clover, 2n = 28) were hybridized and backcrossed four times to T. pratense (BC 1 , BC 2 , BC 3 and BC 4 ), and the seed production and vigor of the backcross progenies were assessed under field conditions. Both female and pollen fertility of the backcross progenies increased as the backcross generations advanced. Female and pollen fertility of BC 4 were 21.3 and 65.3%, respectively. When honeybees were used as pollinators, almost all BC 4 plants produced mature seeds in the field. Most of the BC 1 , BC 2 , and BC 3 plants died by the end of the fourth year in the field, whereas 61% of the BC 4 plants survived for 4 yr. The number of chromosomes in 79% of the BC 4 plants was more than 28, which is greater than that of T. pratense. Differences in leaflet size and shape between BC 4 plants and T. pratense suggest that genes from T. medium were expressed in the BC 4 plants. These results indicate that BC 4 plants may be useful for the improvement of the persistence of T. pratense. Key words: Backcross progeny, breeding material, interspecific hybridization, Trifolium medium, Trifolium pratense