P-071 - Enhancing the efficacy of double stranded RNA for managing soybean fungal diseases

Soybeans are susceptible to fungal diseases that can cause devastating losses, including frogeye leaf spot (FLS), and Asian soybean rust (ASR). Current disease management strategies include the use of resistant cultivars and chemical fungicides. However, there are few soybean cultivars resistant to these diseases, and increasing resistance of pathogen to chemical fungicides is threatening to sustainable soybean production. To address this, spray-induced gene silencing (SIGS) via foliar spray of double-stranded RNA (dsRNA) is a promising bio-fungicide. Several dsRNAs produced in Escherichia coli have effectively suppressed FLS and ASR under repeated greenhouse studies. However, poor uptake of dsRNA by leaf tissue and low stability have limited its field application. To overcome these challenges, different nanomaterials have been synthesized to coat dsRNA for enhancing its stability on plant surfaces. Additionally, different commercial adjuvants are being explored to enhance the uptake of dsRNA. Quantification of fungal biomass using qPCR revealed significantly reduced Phakopsora pachyrhizi, the causative agent of ASR by ACE and CYP4 dsRNAs mixed with different adjuvants and nanomaterials. Similarly, Avr4 dsRNA significantly reduced the growth of Cercosporasojina, which causes FLS, as demonstrated by qPCR. Moreover, dsRNAs of AVR4, CB3, and CYP51, mixed with different adjuvants, effectively suppressed FLS in 2024 field trials. These results indicate that the optimized formulation of dsRNA is crucial for the implementation of SIGS in soybean fungal disease management.