EVALUATION OF AGGRESSIVENESS OF FUSARIUM VIRGULIFORME ISOLATES THAT CAUSE SOYBEAN SUDDEN DEATH SYNDROME
S. Li, G.L. Hartman, Y. Chen
Fusarium virguliforme (Akoi, O’Donnell, Homma & Lattanzi), formerly named F. solani (Mart.) Sacc. f.sp. glycines, is the cause of soybean sudden death syndrome (SDS). Over the last 6 years, an international collection of F. virguliforme isolates has been established and maintained at the National Soybean Pathogen Collection Center, University of Illinois at Urbana-Champaign. Using part of the collection, aggressiveness of F. virguliforme isolates to a susceptible soybean cultivar, Great Lakes 3202, was evaluated under controlled conditions in the greenhouse. After an initial evaluation of 123 isolates on soybean, 30 isolates from different geographic origins with different levels of foliar severity were selected to further evaluate both foliar and root severities. Variability of aggressiveness based on measurements of SDS foliar severity, shoot, root, and root lesion lengths, shoot and root dry weights, and total dry weights was found among isolates (P ≤ 0.01). Isolate FSG1(Mont-1), a reference isolate that has been widely used by the soybean community for basic and applied research, caused the greatest reduction in shoot weight and shoot length compared to the non-inoculated control plants, but six isolates caused higher foliar severity and 15 isolates caused longer root lesion length than the isolate FSG1. Isolate FSG5 caused the greatest reduction in root weight among isolates. Knowledge about the variability of the pathogen is important for selection of isolates for testing for broadbased SDS resistant soybean lines.