A microbial fermentation product protection of Glycine max against Phakopsora pachyrhizi through transcriptomics, proteomics and meta-analysis

Abstract

Asian soybean rust (Phakopsora pachyrhizi) is the main soybean disease in Brazil and its management is based on the use of systemic and protective fungicides. However, the narrow range of options and the high variability of the pathogen led to the emergence of insensitive populations, requiring other disease management options. Among them, resistance induction has been proposed. A microbial fermentation product can activate plant defense responses, but the mechanisms by which the product works at the molecular level and its effectiveness considering the different realities of soy production are still unknown. This work aimed to evaluate the effects of a microbial fermentation product (MFP) on the protection of Glycine max against rust through molecular studies (transcriptomics, proteomics and metabolomics) and meta-analysis of tests conducted in the field. In the first chapter, we discuss a review of elicitors and their receptors and in the remaining two chapters we study the effect of an elicitor derived from microbial fermentation (MFP) on soybean protection against P. pachyrhizi. MFP-treated Glycine max cv. Williams 82 had an increase in expression of the PR1, PR2, IPER, PAL and CHS genes, particularly when inoculated with P. pachyrhizi. During RNAseq, several plant pathways associated with pathogens defenses were induced including plant-pathogen interactions, MAPK signaling pathways, phenylpropanoid biosynthesis, glutathione metabolism, flavonoid metabolism and isoflavonoid metabolism. In field conditions, MFP also induced increase in phenol content and peroxidase activity. In the third chapter, we present the result of a meta-analysis to summarize the effects of MFP in Asian soybean rust severity and soybean yield. A total of 24 entries were used and separate random-effects meta-analysis for severity and yield were performed on the log-transformed ratios ( and for severity and yield, respectively). The estimates were used to obtain control efficacy ( ) and yield response ( ) and their respective confidence intervals (95% CI). was 21.1088 (95% CI: 33.1688 to 6.8818), while was 8.3070 (95% CI: 3.8004 to 13.0206). P values for and were 0.0051 and 0.0002, respectively. A mixed effects meta-analysis was then performed to determine the effects of different moderators (type of treatment, disease pressure, number of applications, and timing of the first application) on MFP treatment. All moderators except disease pressure for severity affected and . MFP had better performance when applied by itself ( for alone was 34.249 compared to 4.725 for mixed. for alone was 14.717 compared to 4.019 for mixed) and when applied earlier during the crop season ( were 8.340 and 8.296 and were 24.799 and 8.561 for early and late, respectively). MFP has been shown to trigger plant defenses in soybean and may potentially be used in a disease management system, together with other strategies, to ensure a sustainable agriculture. MFP has been shown to trigger soybean plant defenses and product application strategies for maximum efficiency have been determined. We hope our results can help in planning future trials and in the decision making of MFP application in field conditions.