Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/3/1995
Publication Date: N/A
Interpretive Summary: Sudden death syndrome (SDS) of soybean is caused by some isolates of Fusarium solani. SDS has been reported in most major soybean production areas in the United States. Yield reductions of up to 70% have been reported. Several hundred cultivars and lines have been tested, but none so far has been symptomless. In vitro selection of plants growing in tissue culture for variants with disease resistance can be accomplished using culture filtrates of the fungus. In this study, soybean embryogenic suspension cultures were used to select for resistance to a toxic fungal culture filtrate, and regenerated plants were tested for their resistance to F. solani. The resistance was expressed nearly equally in the R1 and R2 regenerants indicating that the resistance may be heritable and stable. The crude culture filtrate of F. solani SDS-causing isolates was effective in this study as a selective agent for producing plants resistant to F. solani. Further work with embryogenic cultures of other cultivars should provide for the selection of more cultivars with disease resistance. Likewise, additional studies of the progeny are needed to determine if stable, heritable, and useful resistance can be produced which will lead to commercial cultivars with better levels of resistance to SDS.
Technical Abstract: Soybean embryogenic suspension cultures established from immature cotyledons of cvs. Asgrow A3427 (A3427), Chamberlain, Jack, and Spencer were selected for resistance to the toxic culture filtrate of Fusarium solani, the causal agent of sudden death syndrome (SDS) of soybean. The embryogenic cultures were challenged through a series of transfers in a near-lethal concentration of fungal culture filtrate for 1 to 2 months. One plant of each of the cvs. A3427, Chamberlain, and Spencer, and 69 plants of cv. Jack were regenerated (R0 plants). The R1 (185) (first-selfed generation) and R2 (225) (second-selfed generation) plants of cv. Jack regenerants were inoculated with F. solani SDS isolates. Thirty-four days after inoculating the R1 and R2 regenerants: 1% were without foliar symptoms; 29 and 26.2%, respectively, had symptoms only on the unifoliolate leaves or had mild symptoms on both the unifoliolate and trifoliolate leaves; and 70 and 72%, respectively, had severe foliar symptoms. All parental cv. Jack plants had foliar symptoms (11% being mild and 89% severe). These results indicate that selection of embryogenic suspension cultures with toxic fungal culture filtrate can produce soybean plants with resistance to SDS. The resistance was expressed nearly equally in the R1 and R2 regenerants indicating that the resistance may be heritable and stable.