Low Silicon Content in Leaves and Higher Deposition in Roots Is Associated with Lsi Genes in Psathyrostachys juncea: Microscopy, Gene Expression and Genotyping Study

Accessions of Russian wildrye, Psathyrostachys juncea, an important pasture fodder crop, were arranged in group A with high silicon content in leaves and group B with low silicon content. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses revealed low Si accumulation in roots but higher deposition in leaves of plants from group A, whereas, in contrast, plants from group B showed significantly higher Si content in roots but lower in leaves. Three identified PjLsi genes encoding influx and efflux of silicon were differentially expressed, with higher levels in plants from group A, including PjLsi1 and PjLsi3 in leaves, and PjLsi2 in roots, compared to those from group B. A working model was proposed based on differences in microscopy and gene expression analyses. Sanger sequencing revealed one SNP in the conservative gene PjLsi1, and 14 and 29 SNPs in the more polymorphic DNA sequences of PjLsi2 and PjLsi3, respectively. Allele-specific qPCR (ASQ) markers were developed based on optimally identified SNPs and successfully used for genotyping of all three PjLsi genes in a germplasm collection comprising 72 P. juncea accessions. Highly significant differences were found between groups of genotypes in all three PjLsi genes using ASQ markers with corresponding Si content in the studied accessions, including those from groups A and B. The developed ASQ markers can be tested as candidates in marker-assisted selection for genotyping of hybrid breeding lines and for identification of the best P. juncea genotypes with minimal Si content in leaves of pasture fodder crop.