The International Board for Plant Genetic Resources has recently coordinated efforts to augment the world soybean collection. A key step to exploiting the genetic resources of the subgenus Glycine in soybean improvement is obtaining viable hybrids between these species and soybean. Several specific attributes present among the perennial Glycine, and of potential use in soybean improvement can be listed. In broad outline the perennial Glycine exhibits a striking diversity of geno-types and ecological adaptation. Typically, the perennial Glycine species are minor, inconspicuous components of semi-open Eucalyptus woodland. The most promising results of more recent hybridizations are with a newly described species, G. argyrea Tind. The development represents a significant new contribution from wild perennial germplasm. These developments are the assembly of a large and diverse collection, the achievement of hybrids between the perennials and soybean, and the uncovering of diverse sources of resistance to soybean leaf rust.

A newly described wild perennial species of the genus Glycine, Glycine argyrea Tind., was Investigated to determine its cytological relationships within the group. This species is distinctive in the relative ease with which it hybridizes with other species in the subgenus Glycine. It forms fertllie hybrids with at least four other wild species—G. canescens, G. clandestina, G. latrobeana, and G. tomentella. One such fertile hybrid, G. argyrea X G. canescens, was the female parent of the first reported hybrid with G. max, the cultivated soybean, at the diploid level. Doubling the chromosome complement of this sterile hybrid with colchicine failed to restore fertillty, despite apparently normal bivalent formation. Sterile hybrids were formed from crosses between G. argyrea and G. tabacina, and between G. argyrea and G. cyrtoloba. These crosses demonstrated the unusual facility with which the new species enters into interspecific combinations.

Glycine argyrea (Fabaceae), a perennial wild relative of soybean, has a dual flowering strategy of both self-fertilized cleistogamous flowers and chasmogamous flowers on the same plant. Using allozyme polymorphisms the frequency and pattern of outcrossing was determined. The genotypes of seeds from each of several fruit (legumes) per plant were analysed by starch gel electrophoresis, and the maternal genotype inferred. The maximum likelihood estimates of outcrossing rate for the chasmogamous flowers averaged 0.38. The observed level of heterozygosity in the adult population (h = 0.25) compared with the level expected under random mating (h = 0.32) indicated that partial outcrossing was typical of this population. To analyse the mating pattern further, the pollen genotypes of several seeds per legume for pairs of legumes from the same plant were determined. About 35% of fruit from chasmogamous flowers had no genetically detectable outcross progeny, presumably because they were not cross-pollinated effectively. The majority of the remaining fruit had seed which were of mixed origin (both self-fertilized and outcrossed), suggesting that insect pollination does not preclude self-fertilization. As might be expected from this entomophilous pollination system, the pollen of outcrossed seed within one fruit usually (85% of cross-pollinated legumes) came from one male source. Evidence of pollen carry-over was found in the other legumes. The joint distribution of male sources among the pairs of legumes (paired fruit analysis) showed that non-self sources were shared in 30% of pairs. The probability that two outcrossed seeds from the same fruit would be half-sibs was estimated as 0.15, and for two seeds from different fruit on the same plant as 0.42. There is a hierarchy of genetic identity within and among legumes on the same plant, and on different plants, providing scope for the operation of selection at different levels.