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October 3, 2016

Brazilian Scientists Find Rust Resistant Gene in Wild Soy Variety

Soybean rust is probably the most destructive soybean disease and Brazilian farmers have spent billions of dollars combating the disease since it was discovered in Brazil during the 2000/01 growing season. Scientists never discovered how the disease made its way to Brazil, but regardless of how it arrived in Brazil, Brazilian farmers have lost billions of dollars over the last 15 years in control costs and lost productivity.

For the first time in history, scientists from the Brazilian research service Embrapa have announced that they have found a wild soybean variety that is resistant to soybean rust. It was found in one of the 35,000 legume varieties maintained in the Active Germplasm Bank (BAG) maintained at Embrapa-Soybean headquarters in Londrina, Parana. This is the third largest legume germplasm bank in the world and it was developed with cooperation from the United States Department of Agriculture and the University of Sidney. Legume varieties in the bank come from the United States, Asia, Africa, Europe, the Middle East, and Oceania.

A one-gene resistance is a good start, but scientists want to discover varieties with multiple gene resistance in order to help prevent the disease from simply mutating and overcoming the resistance. Scientists will take the newly discovered gene and try to incorporate it into commercial varieties of soybeans, a process that will take a number of years to complete.

In contrast to the type of soybean grown for commercial production (Glycine max), the wild soybean varieties are little studied and little understood. Since the soybean rust disease is native to Asia, it is likely that wild soybeans growing in that region of the world should contain genes making it resistant to the disease.

The function of a germplasm bank is to catalog, propagate and conserve these wild varieties while at the same time to study the varieties and identify their characteristics such as: productivity, growing cycle, disease resistance, taste, drought tolerance, etc. Once catalogued and described, these soybean varieties are then used in breeding programs designed to improve commercial soybean varieties.

In conducting these studies it is always hoped that the resistance to an important disease could be found and that is what appears to be what happened with soybean rust. The soybean variety with the rust resistant gene looks more like a dry bean variety than a soybean variety.

The work done at these germplasm banks is very meticulous and all done by hand in order to avoid contamination between varieties. The seeds are maintained at 5°C and 25% relative humidity which guarantees long-term viability of the seeds. Scientists are also very careful not to introduce new diseases into the country when these varieties are multiplied.