Research Highlights

Finding New Soybean Breeding Prospects to Manage SCN Resistance

By Barb Baylor Anderson

Soybean cyst nematode (SCN) is a persistent threat to soybean growers. Fields infested with SCN are more susceptible to other disease, pest and environmental stresses. And while planting soybean varieties with genetic resistance to SCN has long been the best tool for limiting yield loss, varietal resistance continues to be an issue in achieving the best SCN control.

“We have seen a breakdown in varietal resistance with the appearance of new SCN races capable of overcoming the widely grown PI 88788 source of resistance. It is expected the situation will become rapidly worse,” says Aaron Lorenz, University of Minnesota soybean breeding and genetics associate professor. “Development of varieties with strong resistance is not easy. SCN resistance screening is expensive and laborious. Plus, some commercially available varieties claiming to have SCN resistance do not always have such resistance.” 

Lorenz is principal investigator for a research project funded by the Minnesota Soybean Research & Promotion Council aimed at enhancing the efficiency and efficacy of breeding for SCN resistance. The overall objective is to advance the development of SCN-resistant varieties and provide accurate, unbiased information on commercial variety resistance.

“A major part of this research is to use molecular markers to help select for SCN resistance. We do this in the early generations of our breeding program, which greatly enhances our chances of finding something good in the later stages of the program. Through these efforts, we have released three new public varieties that have good SCN resistance in the last two years,” he says.

“However, the SCN resistance still comes from the PI 88788 source.”

With checkoff funding, Lorenz is looking for new sources of SCN resistance in addition to known, but alternative sources such as the Peking resistance source. 

“As for Peking-type varieties, we have a couple of very exciting ones in the advanced parts of the pipeline,” he says. “One of those is an MG 0 variety, which would be only the second MG 0 Peking-type SCN resistant variety available. Breeder’s seed of both of these varieties is in use this summer. If performance is good again, foundation seed and release will occur next year.”

Newer resistance sources are earlier in the breeding pipeline. One source, PI 567516C, carries a novel SCN resistance gene. Lorenz has used molecular markers to select the resistant lines and is testing them for the first time in yield trials this year. He also continues to make new crosses annually with novel SCN resistance sources hoping to form a base of new germplasm with new resistance sources to help stave off resistance breakdown for many years to come.

“Another activity that was part of this project was to test existing non-88788 SCN resistant varieties using a greenhouse bioassay that includes Race 1 nematodes. Race 1 overcomes 88788-type resistance,” he says. “The goal was to verify the resistance advertised by these commercial varieties so that growers can be assured that what they choose is truly resistant.”

As it turns out, Lorenz says most were resistant, although some were actually susceptible despite being advertised as resistant. A list of varieties that showed good resistance will be published.

Ultimately, Lorenz adds that breeding new soybean varieties, especially against evolving pests like SCN, is a never-ending responsibility. “Having better and cheaper molecular markers for tagging new resistance genes would certainly help,” he says. “We have some now, but they could be better, and we could use more. Actual identification of genes for new resistance sources could be helpful in possibly opening up gene editing approaches in the future.”

Published: Aug 2, 2021