Backcross (BC2‐BC4)‐Derived Fertile Plants from Glycine max and G. tomentella Intersubgeneric Hybrids

Abstract

Wild perennial relatives of the soybean [Glycine max (L.) Merr.] have not been utilized to broaden the genetic base of the crop. This study provides information on production, morphology, cytology, and breeding behavior of backcross (BC2 to BC4)‐derived fertile plants from soybean (2n = 40, genome GG) and G. tomentella Hayata (2n = 78, genome DDEE). The main hurdle was to obtain BC~ plants (G. max cv. Altona) × (G. tomentella, Pl 483218)] → F1, 2n = 59, genome GDE → colchicine treatment (CT) → 2n = 118, GGDDEE × soybean cv. Clark 63 → BC1, 2,n = 76 (expected 2n = 79). Three sterile BC2 plants (2n = 58, 2n = 56, 2n = 55) were produced. Procedures for immature seed‐rescue were utilized to obtain F, amphiploid, BC1 and BC2 plants. Soybean cv. Clark 63 was used as the recurrent parent in the backcrossing programs. The range of chromosome number among BC3 plants was 2n = 41 to 2n = 52, and among BC4 plants was 2n = 40 to 64. A hypertriploid (2n = 64) in BC4 plant originated after fertilization of an unreduced egg (n = 44) by a normal haploid (n = 20) male gamete. Phenotypes of BC3 and BC4 plants were dissimilar but generally resembled closely to the soybean cv. Clark 63. We expect to isolate a series of aneuploid lines from BC3 to BC6 generations that may open up the path to introgress desired traits from wild perennial Glycine species to the cultivated soybean.