The wild side of a major crop: soybean's perennial cousins from Down Under

The accumulation of over 30 years of basic research on the biology, genetic variation, and evolution of the wild perennial relatives of soybean (Glycine max) provides a foundation to improve cultivated soybean. The cultivated soybean and its wild progenitor, G. soja, have a center of origin in eastern Asia and are the only two species in the annual subgenus Soja. Systematic and evolutionary studies of the ca. 30 perennial species of subgenus Glycine, native to Australia, have benefited from the availability of the G. max genomic sequence. The perennial species harbor many traits of interest to soybean breeders, among them resistance to major soybean pathogens such as cyst nematode and leaf rust. New species in the Australian subgenus continue to be described, due to the collection of new material and to insights gleaned through systematic studies of accessions in germplasm collections. Ongoing studies in perennial species focus on genomic regions that contain genes for key traits relevant to soybean breeding. These comparisons also include the homoeologous regions that are the result of polyploidy in the common ancestor of all Glycine species. Subgenus Glycine includes a complex of recently formed allopolyploids that are the focus of studies aimed at elucidating genomic, transcriptomic, physiological, taxonomic, morphological, developmental, and ecological processes related to polyploid evolution. Here we review what has been learned over the past 30 years and outline ongoing work on photosynthesis, nitrogen fixation, and floral biology, much of it drawing on new technologies and resources.