NLR Genes Related Transcript Sets in Potato Cultivars Bearing Genetic Material of Wild Mexican Solanum Species

Abstract

The long history of potato breeding includes the numerous introgressions of resistance genes from many wild species of South and Central America as well as from cultivated species into the breeding genepool. Most R genes belong to the NLR family with nucleotide-binding site–leucine-rich repeat. The aim of this research concerns an evaluation of NLR genes expression in transcriptomes of three potato cultivars (Evraziya, Siverskij, Sudarynya), which combine genetic material from wild and cultivated potato species, and each bears intragenic markers of RB/Rpi-blb1/Rpi-sto1 genes conferring broad-range resistance to late blight. The transcriptomes of the cultivars were compared before and 24 h after the Phytophthora infestans inoculation. The induction of RB/Rpi-blb1/Rpi-sto1 transcript after 24 h of inoculation was detected in the resistant cultivars Siverskij and Sudarynya but not in susceptible cv. Evraziya. This demonstrates the importance of transcriptomic assay for understanding the results of marker-assisted selection and phenotyping. Interestingly, assembling the transcriptomes de novo and analysis with NLR-parser tool revealed significant fractions of novel NLR genes with no homology to the reference genome from 103 (cv. Siverskij) to 160 (S. stoloniferum, 30514/15). Comparison of novel NLRs demonstrated a relatively small intersection between the genotypes that coincided with their complex pedigrees with several interspecific hybridization events. These novel NLRs may facilitate the discovery of new efficient R genes.