Characterization of Soybean mosaic virus resistance derived from inverted repeat-SMV-HC-Pro genes in multiple soybean cultivars.

KEY MESSAGE: Soybean mosaic virus resistance was significantly improved in multiple soybean cultivars through genetic transformation induced by inverted repeat-SMV- HC - Pro genes based on RNAi and post-transcriptional gene silencing. Here, we demonstrate Soybean mosaic virus (SMV) resistance in transgenic soybean plants. Transformation of five soybean genotypes with a construct containing inverted repeat-SMV-HC-Pro genes-induced high-level SMV resistance. Through leaf-painting assays, polymerase chain reaction (PCR) verification and LibertyLink(®) strip detection, 105 T0 and 1059 T1 plants were confirmed as transgene-positive. Southern blotting confirmed insertion of the T-DNA into the genomic DNA and revealed a low-copy integration pattern. Most T0 plants were fertile and transmitted the exogenous genes to their progenies (ratios of 3:1 or 15:1). In the T1 generation, virus resistance was evaluated visually after inoculation with SMV (strain SC3) and 441 plants were highly resistant (HR). SMV disease rating was classified on a scale with 0 = symptomless and 4 = mosaic symptoms with severe leaf curl. In the positive T1 plants, the disease rating on average was 1.42 (range 0.45-2.14) versus 3.2 (range 2-4) for the nontransformed plants. With the T2 generation, 75 transgene-positive plants were inoculated with SC3, and 57 HR plants were identified. Virus-induced seed coat mottling was eliminated in the resistant lines. Analysis of SMV levels in the plants was performed using quantitative real-time PCR and double-antibody sandwich enzyme-linked immunosorbent assays; the results revealed no virus or a gradual reduction over time in the viral content, thereby supporting the visual examination results. This is the first report demonstrating pathogen-derived resistance to SMV induced by inverted repeat-SMV-HC-Pro genes in multiple soybean cultivars. Our findings contribute positively to the study of transgenic SMV-resistance using RNA interference.