CRISPR/CasRx-mediated resistance to Soybean mosaic virus in soybean

Soybean mosaic virus (SMV), an RNA virus, is the most common and destructive pathogenic virus in soybean fields. The newly developed CRISPR/Cas immune system has provided a novel strategy for improving plant resistance to viruses; hence, this study aimed to engineer SMV resistance in soybean using this system. Specifically, multiple sgRNAs were designed to target positive- and/or negative-sense strands of the SMV HC-Pro gene. Subsequently, the corresponding CRISPR/CasRx vectors were constructed and transformed into soybeans. After inoculation with SMV, 39.02%, 35.77%, and 18.70% of T1 plants were confirmed to be highly resistant (HR), resistant (R), and mildly resistant (MR) to SMV, respectively, whereas only 6.50% were identified as susceptible (S). Additionally, qRT-PCR and DAS-ELISA showed that, both at 15 and 30 d post-inoculation (dpi), SMV accumulation significantly decreased or was even undetectable in HR and R plants, followed by MR and S plants. Additionally, the expression level of the CasRx gene varied in almost all T1 plants with different resistance level, both at 15 and 30 dpi. Furthermore, when SMV resistance was evaluated in the T2 generation, the results were similar to those recorded for the T1 generation. These findings provide new insights into the application of the CRISPR/CasRx system for soybean improvement and offer a promising alternative strategy for breeding for resistance to biotic stress that will contribute to the development of SMV-immune soybean germplasm to accelerate progress towards greater soybean crop productivity.