Extreme resistance toPotato Virus Yin potato carrying theRy_stogene is mediated by a TIR-NLR immune receptor

Abstract

Summary Potato virus Y (PVY) is a major potato (Solanum tuberosum L.) pathogen that causes severe annual crop losses worth billions of dollars worldwide. PVY is transmitted by aphids, and successful control of virus transmission requires the extensive use of environmentally damaging insecticides to reduce vector populations. Rysto, from the wild relative S. stoloniferum, confers extreme resistance (ER) to PVY and related viruses and is a valuable trait that is widely employed in potato resistance breeding programmes. Rysto was previously mapped to a region of potato chromosome XII, but the specific gene has not been identified to date. In this study, we isolated Rysto using resistance gene enrichment sequencing (RenSeq) and PacBio SMRT (Pacific Biosciences single‐molecule real‐time sequencing). Rysto was found to encode a nucleotide‐binding leucine‐rich repeat (NLR) protein with an N‐terminal TIR domain and was sufficient for PVY perception and ER in transgenic potato plants. Rysto‐dependent extreme resistance was temperature‐independent and requires EDS1 and NRG1 proteins. Rysto may prove valuable for creating PVY‐resistant cultivars of potato and other Solanaceae crops.

Mapping and DNA sequence characterisation of the Rysto locus conferring extreme virus resistance to potato cultivar ‘White Lady’

“…The highest identity, 42%, was detected between Y-1 and TMV2 (S9 Fig.). Recently, Grech-Baran et al [42] published the genomic sequence of a TIR-NLR immune receptor identified as Ry sto in a dihaploid clone of the cultivar “Alicja”, which has PVY resistance also from S. stoloniferum in its ancestry. Comparison of the two genomic sequences from the putative start and stop codons of the genes revealed 95% identity between TMV2 and Ry sto (S10 Fig.…”

“…Two genes encoding full-length proteins were similar to TMV resistance proteins in tobacco [52] and Y-1 characterising an ER with S. andigena origin in potato [17]. One of these genes, TMV2 , showed 95% identity with the recently isolated Ry sto gene of the dihalpoid clone dH ‘Alicja’ at genomic DNA sequence level [42].…”

“…In contrast, introduction and expression of a TIR-NLR gene derived from ‘Alicja’ and mapped to the same 58-59-Mbp region of chromosome XII as the TIR-NLR genes we identified transferred ER to two sensitive potato cultivars, ‘Russet Burbank’ and ‘Maris Piper’. This gene, which was identified as Ry sto in ‘Alicja’ [42], is 95% identical with TMV2 in ‘White Lady’ at genomic sequence level. Even the primer pair used to clone Ry sto from ‘Alicja’ may be suitable for cloning TMV2 from ‘White Lady’ (S10 Fig.).…”

“…An alternative explanation might be the high frequency of chimera formation generated by Agrobacterium -mediated transformation and regeneration from calluses [53]. Since a slightly different transformation technique was used by Grech-Baran et al [42] and us, and the frequency of chimera formation may be different in various potato cultivars, these factors could result in a difference in the frequency of chimera formation. Since chimeras have untransformed cells the viruses could spread and multiply in these cells masking the resistant phenotype of the transgenic cells when testing the plants for the presence of the virus by RT-PCR.…”

Farmers’ Knowledge of Potato Viruses and Management Strategies in the Western Highlands of Cameroon

“…This process requires the search for resistance genes and their incorporation into potato genotypes. This is the case of the Rysto gene taken from Solanum stoloniferum which is grafted onto chromosome number 12 of the potato and which confers resistance to the different strains of Potato virus Y (PVY) [22].…”