Cytogenetics and genetic introgression from wild relatives in soybean

Abstract

Cultivated soybean, wild soybean, and 23 perennial Glycine species contain 2n = 40 chromosomes. Accessions of G. hirticaulis and G. tabacina have diploid (2n = 40) and tetraploid (2n = 80) chromosome numbers. In contrast, G. tomentella includes accessions with four cytotypes (2n = 38, 40, 78, or 80). Meiosis of G. max and G. soja F1 is normal and gene exchange is easy. Occasionally, accessions of the two species differ by chromosome structural changes (reciprocal translocation/paracentric inversion). The segregating populations inherit undesirable traits such as vining, lodging susceptibility, lack of complete leaf abscission, seed shattering, and small black coated seeds because of genetic drag. The introgression of useful genes from 26 wild perennial Glycine species to soybean has been restricted because of crossability barriers and requires extensive hybridization, immature seed rescue, and cytogenetic manipulations. This review paper discusses cytogenetics, gene pools of the soybean and the production of fertile G. max plants using 78-chromosome G. tomentella (PI 441001) as a paternal and maternal parent in crosses with G. max cv. ‘Dwight’ (2n = 40). Thus, reporting breaking of the intersubgeneric crossability barriers for the first time.