Methods for producing fertile crosses between wild and domestic soybean species

#This invention Soybean is economically an important crop for feed, oil and other soy products. However, the genetic base of soybean cultivars grown in the United States is extremely narrow. Recent screening of domestic soybean varieties, plant introductions and other accessions at Ft. Detrick Maryland has shown all the varieties tested to have some level of susceptibility to soybean rust isolates recently collected from Asia, Africa, and South American. Most currently-available soybean varieties with sources of resistance to multiple strains of soybean cyst nematode are genetically similar, which indicates that finding new genes for resistance to soybean cyst nematode in domestic soybean germplasm may be difficult.

#Soybean rust and cyst nematodes are economically damaging pathogens that threaten soybean production fields within the United States and elsewhere. Soybean rust (SBR) is a foliar soybean disease capable of causing significant economic yield loss (Bromfield, K. R. 1984, “Soybean Rust,” Monogr. 11, American Phytopathological Society, St. Paul, Minn.; Ogle, H. J., D. E. Byth, and R. McLean, 1979, “Effect of rust (Phakopsora pachyrhizi) on soybean yield and quality in southeastern Queensland, Australia,” Aust. J. Agric., Res. 30:883-893; Sinclair, J. B., 1989, “Threats to production in the tropics: Red leaf blotch and leaf rust,” Plant Dis., 73:604-606). In recent years, soybean rust has reduced yields and raised production costs for soybeans in every major production region of the world except the United States. Two fungal species, Phakopsora pachyrhizi Sydow (also known as the Asian species) and P. meibomiae (Arthur) Arthur (also known as the New World species), cause soybean rust and are spread primarily by windborne spores that can be transported over long distances. Asian soybean rust, P. pachyrhizi, the more aggressive of the two species, was first reported in Japan in 1903 and was confined to the Eastern Hemisphere until its presence was documented in Hawaii in the mid-nineties. Soybean rust in the continental United States was first confirmed in November of 2004 (Harmon, P. F., M. T. Momol, J. J. Marois, H. Dankers, and C. L. Harmon, 2005, “Asian soybean rust caused by Phakopsora pachyrhizi on soybean and kudzu in Florida,” Online Plant Health Progress, doi:10.1094/PHP-2005-0613-01-RS).

#The number of states with confirmed soybean rust cases in the United States as of the end of 2005 stands at ten. The presence of soybean rust in Louisiana, Mississippi and Florida had been confirmed by USDA's Animal and Plant Health Inspection Service within a week of the initial discovery in Louisiana. Subsequent sampling resulted in confirmations of rust on soybeans in Alabama, Georgia, Arkansas, Missouri, South Carolina, Tennessee, and Texas. The species of soybean rust found on all positive samplings is Asian soybean rust (P. pachyrhizi), the more aggressive of the two species. The timing and distribution of soybean rust growth in the southeastern U.S. is consistent with spores having been brought from South American by Hurricane Ivan.

#This patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

#FIG. 1 is a schematic diagram showing the methods of this invention for producing hybrids between wild perennial Glycine species and domestic annual soybean cultivars.

#FIG. 2 is a graph showing the ionic concentration of the Singh seed maturation medium and Singh shoot elongation (C5) media of this invention compared with commercial Murashige and Skoog (MS) and Gamborg B5 media.

#As shown in FIG. 1, this invention provides a scheme for introgressing genes from wild perennial Glycine species (also referred to herein as “wild soybean”) into domestic annual Glycine cultivars (also referred to herein as “domestic soybean”). The method includes crossing (designated by the “X” in the Figure) a domestic soybean, designated “Glycine max” in the Figure with a wild soybean, designated “Glycine tomentella” in the Figure. Although the scheme illustrates the invention with reference to this particular wild soybean species, other wild soybean species can be substituted for Glycine tomentella.

#Glycine max has 40 chromosomes (2n=40), and a G1G1 genome, more fully explained below. As is known in the art, the Glycine tomentella accessions PI441001 and PI441008 used to illustrate the invention have 78 chromosomes (2n=78), and a genome D3D3EE. Other Glycine tomentella accessions have differing numbers of chromosomes and different genomes.

#As shown by the first down arrow in FIG. 1, the cross produces an F1 hybrid having 59 chromosomes (2n=59) and a genome (G1D3E). The hybrid has inherited half the total number of chromosomes present in each parent, 20 chromosomes from the domestic soybean parent and 39 from the wild soybean parent. These hybrid plants may be screened to identify plants that have retained desirable traits and/or genes from the wild parent plants for further breeding.