Characterizing the Effect of Foliar Lipo-chitooligosaccharide Application on Sudden Death Syndrome and Sclerotinia Stem Rot in Soybean

Abstract

Lipo-chitooligosaccharides (LCOs) are signal molecules produced by plant root endosymbionts and have been identified, formulated, and marketed as growth-promoting adjuvants for soybean (Glycine max [L.] Merr.). Experiments were conducted under controlled environmental conditions to characterize the effects of foliar LCO applications on early symptom development of sudden death syndrome (SDS), caused by Fusarium virguliforme, and Sclerotinia stem rot (SSR), caused by Sclerotinia sclerotiorum. Treatment factors for the SDS experiment included two soybean cultivars (Sloan and CH2105R2), two inoculation levels (noninoculated control and inoculated), and two LCO applications (control and foliar LCO application), whereas two experimental soybean lines (91-38 and 91-44) and two LCO applications (water control and foliar LCO application) were used in the SSR experiment. The LCO application did not significantly influence SDS root symptom severity or early-season growth characteristics. However, on the susceptible line (P = 0.01) and with LCO application (P = 0.03), significantly larger SSR lesions developed compared with the nontreated control and resistant line. These results suggest foliar-applied LCOs have a limited effect on early root symptom development caused by F. virguliforme but increase stem symptom development caused by S. sclerotiorum.