Backcross‐Derived Progeny from Soybean and Glycine tomentella Hayata Intersubgeneric Hybrids

Abstract

Wild perennial species of the subgenus Glycine Willd, have not been exploited in soybean [Glycine max (L.) Merr.] breeding programs. This paper discusses wide hybridization in the genus Glycine and reports on the origin, identification, and breeding behavior of a synthesized amphiploid soybean ✕ G. tomentella Hayata hybrid and its backcross‐derived progeny. Amphiploid H213‐2a (2n = 118) plants showed almost normal meiotic pairing (0.711 + 57.9811 + 0.33IV), but later meiotic stages were abnormal, showing laggards and bridges, and the plants set only a few pods. The F2, F3, and F4 plants carried the expected 2n = 118 chromosomes, and thus were cytologically stable. A growth‐hormone solution containing 100 mg gibberellic acid (GA3), 25 mg naphthalene acetic acid (NAA) and 5 mg kinetin/L distilled water was sprayed onto the pollinated gynoecia to enhance pod retention (14.19%) in H213‐2a ✕ soybean crosses. Without daily hormone spray, only three pods of the 3417 florets pollinated were harvested 19 to 21 d after pollination. The BC1 plants were obtained in two cross combinations: (i) H213‐2a ✕ ‘Clark 63’ = H562, and (ii) H213‐2a ✕ ‘Essex’ = H564. The H562 plants contained 2n = 76, (BC1; expected 2n = 79), suggesting the loss of three chromosomes. The H564 plants contained 2n = 98 chromosomes and may have originated by the union of a female gamete (n = 59) and an unreduced male (n = 40) spore. All the BC1 plants were totally sterile, and attempts are being made to generate BC2 plants.