Evaluation of soybean germplasm for resistance to Fusarium virguliforme, the major pathogen causing sudden death syndrome of soybean in the United States

Sudden death syndrome (SDS) is one of the most important yield limiting diseases of soybean [Glycine max (L.) Merr.]. In North America, the most common causal species is Fusarium virguliforme O'Donnell & T. Aoki. Yield losses of up to 80% have been reported. Host resistance is among the most sustainable tools to reduce SDS losses, and screening soybean accessions for sources of resistance is a fundamental part of discovering host resistance. This study evaluated 10,144 soybean plant introductions (PIs) in soybean maturity groups (MGs) 000 to X for resistance to F. virguliforme. Using a tiered testing sequence and a seedling-layered inoculum method in the greenhouse, new sources of resistance were identified. In tier VI, 81 of 125 PIs evaluated had mean foliar severity that was equal to or significantly lower than that of the resistant check, PI 567374. In tier VII, 20 PIs with low foliar severity scores representing a range of MGs were further evaluated for foliar response, as well as "relative dry weights"-dry shoot and root weights expressed as a percentage of respective noninoculated plants. At 28 days after planting, 16 PIs had mean foliar severity ratings not significantly different from PI 567374; three of these PIs, 279081, 506757, and 507568, had significantly greater relative dry shoot, root, and total weight than PI 567374. The highly resistant entries reported here will be useful for further studies to understand the resistance mechanisms to F. virguliforme and for breeding programs focused on increasing SDS resistance in elite breeding lines.