Interspecific hybrids between the soybean and wild perennial relatives

Abstract

Successful crosses were obtained in 390 different genotype combinations between the soybean, Glycine max (L.) Merr., and wild perennial Glycine species. A total of 1534 Immature embryos were excised prior to abortion and cultured, and 1.4 percent of these germinated to produce shoots representing 18 genotype combinations. Sixteen F1 Interspecific hybrids encompassing 12 different combinations were subsequently grown to maturity: 7 G. max (2n = 40) × G. tomentella Hayata (2n = 78), 3 G. tomentella × G. max, and 2 G. canescens F. J. Herm. (2n = 40) × G. max. The F1 hybrids differed morphologically depending on the genotype combination, and showed variable degrees of anther development. Hybrids with wild Glycine as the female parent gave the most normal anther development. Expected chromosome numbers of 2n = 59 and 2n = 40 were confirmed for G. tomentella and G. canescens hybrids, respectively. The F1 hybrids exhibited low chromosome pairing and perturbed melosis in pollen mother cells and were sterile. Eight hybrid combinations were doubled with colchicine to give 2n = 118 and 2n = 80 chromosomes for G. tomentella and G. canescens hybrids, respectively. Doubled plants exhibited high levels of chromosome pairing as expected, but remained highly sterile because of abnormal microspore formation. Fertility was partially restored in one G. max × G. tomentella (2n = 118), which set mostly one-seeded, cleistogamous pods at a low rate. Chromosome numbers of selfed progeny were similar to the doubled parent. Variation in viability and fertility shown by different hybrid combinations within one interspecific cross indicate that genotype interactions play a large part in determining the ease with which hybrids can be made between wild perennials and the soybean, and will most likely influence which Glycine collections represent potential candidates for gene exchange with the soybean.