The influence of soybean mosaic virus on the yield of transgenic soybean and studying of its molecular genetic properties

Abstract

Despite the harmful impact of the Soybean mosaic virus (SMV), new soybean varieties, which are resistant to plant pathogens of various etiologies, are intensively developed and introduced. However, mainly, varieties have combined resistance to abiotic factors and fungal and / or bacterial soybean diseases. On the country's market there are varieties of genetically modified soybean that are characterized by high productivity and resistance to disease. The aim of the work was to investigate the influence of Soybean mosaic virus on yield of transgenic Glycine max plants and to study the molecular and genetic properties of the SMV isolate. Biometric measurements, as well as yield and its structure; DAS-ELISA, total RNA extraction from plant material, RT-PCR, sequencing, phylogenetic analysis, statistical methods were used in the study.

For the first time in Ukraine, it has been shown that transgenic soybean is affected with Soybean mosaic virus. It was found that SMV significantly reduces the yield of GM-soybean plants. The yield of SMV-infected soybean decreased in both investigated farms in Kyiv and Poltava regions by 35.0-65.7% respectively. A more significant decline in the yield (2.6 times) of SMV-infected soybean was noted in the Poltava region in conditions of very arid climate in 2017 (HTC = 0.53) comparing with 2016. It was noted that the SMV infection has a negative effect on the productivity and structure of the yield of GM-soybean plants. SMV infection reduces the number of beans by 21.9% and the number of grains per plant by 22.5%, the weight of grain from one plant - by 27.1% and the weight of 1000 grains - by 29.7% in comparison with healthy plants.

To establish the strain identity and the origin of the SMV isolate SGP-17, its DNA sequence was compared to sequences of 33 SMV isolates and strains from Gene Bank. The phylogenetic analysis of the nucleotide sequences of the part (430 bp) of the capsid protein gene (CP) (positions 8640-9069 b.) of the studied isolate SGP-17 showed that the highest percentage of homology (97.9%) in the nucleotide sequence it has with the Iranian isolates Ar33, Lo3, American VA2 and Ukrainian UA1Gr. Also, a high level of nucleotide homology was observed with Chinese isolates HB-S19, XFQ014, Polish isolate M, Iranian Go11, and American strain 1083 (96.7-97.6%). SGP-17 isolate, together with these isolates, as well as the Japanese strain C, is grouped in one branch of phylogenetic ML tree, indicating their common origin. The multiple alignment of the amino acid sequences of the CP region of SMV isolates/strains revealed four unique amino acid substitutions in the CP gene region of the SGP-17 isolate in positions 1-4 (Ser → Trp; Lys → Cys; Gly → Met; Lys → Glu, respectively). To explore the evolutionary forces acting on the SMV CP gene, the dN/dS values were calculated for all of the SMV CP sequences included to the study. This ratio indicates the amount of nonsynonymous to synonymous mutations. The global dN / dS ratio for all sequences taken to the study was 0.0386 (p <0,01). For SGP-17 isolate dN/dS is 0.0651, while for all other isolates it ranged from 0.0149 to 0.0578. That is, the Ukrainian isolate SGP-17 has a higher divergence of nucleotides in comparison with the SMV isolates from other countries. High levels of revealed nucleotide divergence and four unique amino acid substitutions can be implicated in the ability of this isolate to infect transgenic soybean plants. The obtained results testify in favor of growing of domestic soybean varieties, created by classical selection methods and containing determinants of natural genetic resistance to the SMV.

Keywords: Glycine max, Soybean mosaic virus, yield, phylogenetic analysis, molecular and genetic properties