Intersubgeneric hybridization between Glycine max and G. tomentella: production of F₁, amphidiploid, BC₁, BC₂, BC₃, and fertile soybean plants

Key message: This paper describes methods for unlocking genetic treasure from wild perennialGlycinespecies of Australia for soybean improvement. Abstract: The genetic resources of the ca. 26 species of the genus Glycine subgenus Glycine have not been exploited to broaden the genetic base of soybean (Glycine max; 2n = 40). The objectives of this study were to develop methods for producing F₁, amphidiploid, BC₁, BC₂, BC₃, and fertile soybean plants from crosses of soybean and the genus Glycine subgenus Glycine species, in order to utilize the subgenus Glycine germplasm in soybean breeding. Soybean cultivars were hybridized with six accessions of 78-chromosome G. tomentella as well as one accession each of 40-chromosome G. tomentella, G. argyrea and G. latifolia. They were chosen because they exhibit resistance to soybean rust. We were successful in producing fertile soybean from soybean cv. ‘Dwight’ and 78-chromosome G. tomentella accession PI 441001, while other hybrids were discontinued either at F₁ or amphidiploid stage. The F₁ seeds aborted prior to reaching maturity, so developing seeds from 19 to 21 day old pods were cultured aseptically in various media formulations. Seed maturation and multiple embryo generation media were developed. F₁ plants with shoots and roots (2n = 59) were transplanted to pots in greenhouse. Amphidiploid (2n = 118) plants were backcrossed to ‘Dwight’. BC₁ (2n = 79) plants were propagated through in vitro and 43 mature BC₂F₁ seeds were harvested. Fifteen surviving BC₂F₁ plants were morphologically distinct, sterile, and had chromosome numbers ranging 2n = 56–59. Chromosome numbers of the BC₃F₁ plants ranged 2n = 40–49. Derived fertile soybeans were first planted in the field in 2008 and are being evaluated for yield, resistance to pathogens and pests and tolerance to salt through material transfer agreement.