Cassava mosaic disease (CMD) is a major disease affecting cassava production in Southeast Asia. This study aimed to perform an integrated proteomics and metabolomics analysis of cassava cv. Kasetsart 50 infected with Sri Lankan cassava mosaic virus (SLCMV). Proteomics analyses revealed that 359 proteins were enriched in the plant–pathogen interaction, plant hormone signal transduction, and MAPK signaling pathways. A total of 79 compounds were identified by metabolomics analysis of the healthy and SLCMV-infected cassava plants. Integrated omics analysis revealed that 9 proteins and 5 metabolites were enriched in 11 KEGG pathways. The metabolic pathways, plant hormone signal transduction, and plant–pathogen interaction pathway terms were specifically investigated. The findings revealed that caffeic acid and chlorogenic acid were associated with the plant–pathogen interaction pathway, histidine (HK3) was involved in plant hormone signal transduction, while citric acid and D-serine were associated with the metabolic pathways. KEGG functional enrichment analysis revealed that plant–pathogen interaction, plant hormone signal transduction, and metabolic pathways were linked via the enriched protein (protein phosphatase 2C) and metabolites (cyclic nucleotide-binding (AT2G20050) and D-serine). The available information and resources for proteomics and metabolomics analyses of cassava can elucidate the mechanism of disease resistance and aid in cassava crop improvement programs.

Background: Cassava mosaic disease (CMD), caused by the Sri Lankan cassava mosaic virus (SLCMV), significantly increases cassava yield losses in Thailand, with losses ranging from 30% to 80%, and is exacerbated by limited access to healthy planting materials. Methods: This study explored salicylic acid (SA) as a potential treatment for enhancing disease resistance in CMD infected cassava plants. SA was applied at 100 and 200 mg/mL, and its effects were evaluated using quantitative real-time polymerase chain reaction (qPCR) and reverse transcription qPCR (RT-qPCR) to measure viral loads and the expression levels of resistance genes. Results: Although SA treatment did not considerably affect disease severity, foliar CMD symptoms visibly decreased, particularly with 200 mg/mL SA, which also reduced SLCMV particle counts at 1- and 2-weeks post-treatment. SA upregulated the expression of pathogenesis-related proteins (PRs), including HSP90.9, WRKY59, SRS1, and PR9e. Additionally, SA enhanced the regulation of secondary metabolite pathways involving L-serine within the glycine, serine, and threonine metabolism, as well as the phenylpropanoid biosynthesis pathways. Conclusions: These findings collectively indicate that SA enhances resistance through the systemic acquired resistance (SAR) pathway and can serve as a potential strategy for the management of CMD, particularly in regions where healthy cassava planting materials are scarce. The study highlights the efficacy of SA in reducing viral particles, inducing the immune response, and providing a promising approach for controlling CMD.

Cassava mosaic disease (CMD) is caused by viruses such as Sri Lankan cassava mosaic virus (SLCMV). It poses a significant threat to the cassava (Manihot esculenta) yield in Southeast Asia. Here, we investigated the expression of WRKY transcription factors (TFs) in SLCMV-infected cassava cultivars KU 50 (tolerant) and R 11 (susceptible) at 21, 32, and 67 days post-inoculation (dpi), representing the early, middle/recovery, and late infection stages, respectively. The 34 identified WRKYs were classified into the following six groups based on the functions of their homologs in the model plant Arabidopsis thaliana (AtWRKYs): plant defense; plant development; hormone signaling (abscisic, salicylic, and jasmonic acid); reactive oxygen species production; basal immune mechanisms; and other related hormones, metabolites, and abiotic stress responses. Regarding the protein interactions of the identified WRKYs, based on the interactions of their homologs (AtWRKYs), WRKYs increased reactive oxygen species production, leading to salicylic acid accumulation and systemic acquired resistance (SAR) against SLCMV. Additionally, some WRKYs were involved in defense-related mitogen-activated protein kinase signaling and abiotic stress responses. Furthermore, crosstalk among WRKYs reflected the robustly restricted viral multiplication in the tolerant cultivar, contributing to CMD recovery. This study highlights the crucial roles of WRKYs in transcriptional reprogramming, innate immunity, and responses to geminivirus infections in cassava, providing valuable insights to enhance disease resistance in cassava and, potentially, other crops.