A microbial fermentation product induces defense-related transcriptional changes and the accumulation of phenolic compounds in Glycine max.

Abstract

With the progressive loss of fungicide efficacy against Phakopsora pachyrhizi, the causal agent of Asian soybean rust (ASR), alternative methods to protect soybean crops are needed. Resistance induction is a low impact alternative and/or supplement to fungicide applications that fortifies innate plant defenses against pathogens. Here, we show that a microbial fermentation product (MFP) induces plant defenses in soybean and transcriptional induction is enhanced with the introduction of ASR. MFP-treated plants exhibited 1,011 and 1,877 differentially expressed genes (DEGs) 12 and 60 hours after treatment, respectively, compared to water controls. MFP plants exposed to the pathogen 48 h after application and sampled 12 hours later (for a total of 60 h) had 2,401 DEGs compared to control. The plant defense genes PR1, PR2, IPER, PAL, CHS were induced with MFP application and induction was enhanced with ASR. Enriched pathways associated with pathogen defense included plant-pathogen interactions, MAPK signaling pathways, phenylpropanoid biosynthesis, glutathione metabolism, flavonoid metabolism and isoflavonoid metabolism. In field conditions, elevated antioxidant peroxidase activities and phenolic accumulation were measured with MFP treatment, however improved ASR control or enhanced crop yield were not observed. MFP elicitation differences between field and laboratory grown plants necessitates further testing to identify best practices for effective disease management with MFP-treated soybean.