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.

Soybean mosaic virus (SMV) commonly affects soybean production worldwide, and the SC18 strain has been widespread in China. This study aimed to characterize and map the SC18 resistance genes present in soybean cultivars 'Kefeng No.

Soybean mosaic virus (SMV), belonging to the genus Potyvirus of the family Potyviridae, has a relatively narrow host range almost exclusively confined to leguminous hosts. While disease management through genetic transformation can be an effective approach, soybean remains recalcitrant to routine genetic transformation. In this context, it is important to identify new hosts for SMV that can be used to develop effective transgenic resistance strategies. Transformation in Nicotiana benthamiana is simple and highly efficient; hence, here we demonstrate the infectivity of SMV strain SC7 in N. benthamiana plants. To identify an SMV strain infectious in N. benthamiana, we mechanically inoculated N. benthamiana plants with 37 isolates from 21 (SC1 to SC21) SMV strains. Plants inoculated with isolates of strain SC7 produced mosaic symptoms on leaves. However, N. benthamiana plants inoculated with the 20 other SMV strains showed no visible symptoms. Furthermore, soybean cv. Nannong 1138-2 inoculated with sap prepared from symptomatic N. benthamiana leaves showed typical SMV mosaic symptoms 2 weeks after inoculation. In addition, SMV was detected in symptomatic N. benthamiana and soybean leaves by RT-PCR, DAS-ELISA, and further identified by sequencing. Together, the results indicate that N. benthamiana plants could support multiplication of SMV strain SC7. The findings of this study would be useful for the investigation of SMV resistance using the model plant N. benthamiana.

Soybean mosaic virus (SMV) is one of the most destructive pathogens of soybean (Glycine max (L.) Merr.) worldwide. In this study, 184 F7:11 recombinant inbred line (RIL) populations derived from Kefeng No. 1 × Nannong 1138-2 were used to study the inheritance and linkage mapping of resistance genes against SMV strains SC7 and SC13 in Kefeng No. 1. Two independent dominant genes (designated Rsc7 and Rsc13) that control resistance to SC7 and SC13 were located on a molecular linkage group (MLG) of chromosome 2 (D1b). A mixed segregating population was developed by self-pollination of three heterozygous plants of residual heterozygous lines (RHL3-27, RHL3-30, RHL3-53) with five markers linked to the loci, and was used in fine-mapping of Rsc7 and Rsc13. In addition, Rsc7 was fine-mapped between BARCSOYSSR_02_0667 and BARCSOYSSR_02_0670 on MLG D1b. The genetic distance between the two closest markers was 0.7 cM and the physical distance of the interval was ~77 kb, which included one LRR gene and another gene containing an F-box region. Two SSR markers (BARCSOYSSR_02_0610 and BARCSOYSSR_02_0621) were closely linked to the SC13 resistance gene. The physical distance where Rsc13 was located was ~191 kb. Sequence analysis showed that there were two K-box region types of transcription factor genes; GmHSP40 and two serine/threonine protein kinase (STK) genes were the most likely candidate genes. These results will facilitate map-based cloning of the Rsc7 and Rsc13 genes and development of transgenic disease-resistant varieties, and will provide SMV-resistance breeding systems with excellent resistance germplasm.