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Agronomy Day 2010

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Tour A

Perennial Glycine: A new source of genetic diversity for soybean improvement

Randall Nelson
Randall Nelson,
USDA-ARS Research Geneticist,
Department of Crop Sciences,
217-244-4346,
randall.nelson@ars.usda.gov
Ram Singh
Ram Singh, Agronomist,
Department of Crop Sciences,
217-333-8144,
ramsingh@illinois.edu
Justin Ma
Justin Ma,
Graduate Research Fellow,
Department of Crop Sciences,
217-333-3155,
ma16@illinois.edu
Soybean by G. tomentella hybrid	plant growing in culture in the	laboratorySoybean by G. tomentella hybrid plant growing in culture in the laboratory

Perennial Glycine species are very distant relatives of soybean.  Unlike soybean that is native to China, all 26 perennial Glycine species are native to Australia and have been genetically isolated from soybean for several million years.  Some of these species thrive in environments in which soybeans would not survive. These perennial species represent a rich and unused source of new genetic diversity for long term soybean improvement.  It is not possible cross these species with soybean using standard procedures, but we have developed techniques that allow us to cross one perennial species, Glycine tomentella, that has 78 chromosomes with soybean that has 40 chromosomes.  The hybrid seed must be rescued from the plant shortly after pollination, or it will abort.  This immature seed is cultured in the laboratory to produce a plant that has half of the chromosomes from each parent for a total of 59.  It is completely sterile because parental chromosomes are very different.  By treating this plant with a chemical called colchicine we can double the chromosomes to produce a plant with a full complement of chromosomes from both species.

Two soybean plants that have	different numbers of G. tomentella chromosomesTwo soybean plants that have different numbers of G. tomentella chromosomes

This plant will produce a few seeds but it is essentially a new species and has no direct use for soybean breeding.  We cross this plant back to soybean and repeat the seed rescue procedure.  This hybrid plant has all of the soybean chromosomes and half of the chromosomes from G. tomentella.  This plant is not self fertile but it can be crossed again to soybean.  As this procedure is repeated, we randomly lose the G. tomentella chromosomes because they have no pairing partner.  Plants with 1 or 2 G. tomentella chromosomes and 40 soybean chromosomes are generally self fertile and can produce progeny that are normal soybean plants with 40 chromosomes or genetically stable plants with 42 chromosomes, 20 pairs of soybean chromosomes and 1 pair of G. tomentella chromosomes.  Evaluation of the lines with 42 chromosomes allows us to determine if there are any useful genes on that pair of G. tomentella chromosomes.  During the process of creating soybean lines with 40 chromosomes, genes from G. tomentella are transferred into the soybean.  With only limited testing over the past 2 years, we have identified soybean lines with genes from G. tomentella that change oil and protein concentration, plant height, flower color, and the time of maturity.  None of these changes are economically important for soybean breeders, but they demonstrate that it is possible to tap into this valuable source of unused genetic diversity.  We have found two genes for resistance to Phytophthora rot transferred from G. tomentella and we are currently determining the relationship of these genes to those known in soybean.  We are currently extensively screening derived soybean lines for the very high levels of resistance to soybean rust and soybean cyst nematode that exist in the G. tomentella parent.  We will continue to expand this breeding program to create and evaluate more soybean lines for new genes from G. tomentella that can provide resistance to important pests and pathogens, tolerate environmental stresses, and possibly increase yield.

Agronomy Day 2010