Chromosome Transmission and Morphology of Three Primary Trisomics in Soybeans (Glycine Max)

Two primary trisomics in soybeans (Glycine max (L.) Merr.), Tri A and Tri B that arose from an asynaptic mutant, did not differ in morphology from each other or from their respective diploid sibs. The third primary trisomic, Tri C, which arose from a desynaptic mutant, showed slight morphological deviation from its diploid sib. There was no relationship between seed weight and somatic chromosome number among the progeny of the three trisomics. Self-pollination of the three trisomics yielded approximately 50% 2n + 1 offspring but only 3% 2n + 2 progeny. Intercrosses among the three trisomics gave approximately 50% 2n + 1 F1 progeny and yielded 13% 2n + 1 + 1 progeny. The rate of ovule transmission of the extra chromosome was 34% for Tri A, 45% for Tri B, and 39% for Tri C. The rate of pollen transmission of the extra chromosome was 27% for Tri A, 22% for Tri B, and 43% for Tri C. Soybeans can tolerate an extra chromosome without any appreciable detrimental effect on the gametophyte or the sporophyte. These results are in harmony with the supposed polyploid nature of soybeans.