Strategies for Major Virus Diseases of Corn and Soybeans
Virus disease management in corn and soybeans can be improved using new and previously-discovered genetic sources of host plant resistance.
Viruses seriously limit yield production in corn, soybean, and other crops in Ohio and around the world. Because there are no chemical treatment options for viruses, the most cost-effective management is the use of resistant varieties. In Ohio, resistant varieties are important to minimize losses due to Maize dwarf mosaic virus (MDMV), Sugarcane mosaic virus (SCMV), and related viruses that cause maize dwarf mosaic disease, such as Johnsongrass mosaic virus (JGMV) and Sorghum mosaic virus (SrMV).
However, the recent emergence of resistance-breaking virus isolates threatens this approach to disease management. With soybeans, Alfalfa mosaic virus (AMV), Bean pod mottle virus (BPMV), and Soybean mosaic virus (SMV) can substantially reduce yield, but also cause seed coat mottling, which directly impacts the sales of high quality food grade soybeans, one of Ohio’s top export crops. There is no known adequate resistance for any of these soybean viruses in commercial varieties.
Scientists developed corn lines with highly defined combinations of three genes for virus resistance in a genetically desirable, but virus susceptible, background. Tests of these lines indicated differential resistance to three different potyviruses. Two corn virus isolates, MDMV-It and SCMV-OH, were found to break resistance to the strongest and most frequently deployed resistance gene, Wsm1. However, when another resistance gene (Wsm2) was present in addition to Wsm1, the plants did not become infected. A third gene, Wsm3, could dramatically boost the resistance provided by Wsm1. For soybeans, OARDC and Univ. of Nebraska researchers are generating transgenic soybean plants that confer resistance to all three viruses with a single transgene. Greenhouse experiments indicate that these transgenic plants are highly resistant to AMV, BPMV and SMV, even when all three viruses are introduced into the plants simultaneously. The transgenic plants will be further assessed in field experiments.
Resistance is the primary sustainable form of disease management for viruses of field crops. We have shown that a commonly used resistance gene in corn, Wsm1, is active against multiple viruses causing maize dwarf mosaic disease including the less common viruses JGMV and SrMV. Our data also indicate that this gene is also active against an unrelated virus causing High Plains disease. Results further indicate that developing corn lines with multiple virus resistance genes can provide more effective disease control. The new lines developed in this study will be used by corn breeders to develop locally-adapted, virus-resistant hybrids, leading to higher and more stable corn yields, for both food and biofuel production. Moreover, because of the lack of naturally occurring resistance to soybean viruses, these genetic tools will be essential for sustainable management of the three soybean viruses and crucial for the production of food-grade soybeans.