Opening the doors of potato pathogen perception - New research identifies one of the best genes to confer durable resistance against late blight in potato

Late blight (Phytophthora infestans), the cause of the Irish potato famine in the 1840s, continues to reduce potato yields today and can cause devastating losses. Resistance genes in plants provide protection by allowing the plant to perceive pathogenic microorganisms and upon perception, activate defence against them. However, single resistance genes often act against a limited range of pathogen races and can be overcome by new variants.

The challenge is to find new resistance genes that provide protection against the widest range of pathogens and their variants, buying time in an ongoing evolutionary arms race.

To address this challenge, Professor Jonathan Jones and his co-workers explored the diversity of resistance genes in a wide range of wild Solanum plants related to potato. They found Solanum americanum, the ancestor of the widespread UK wild plant Solanum nigrum (black nightshade) to be an excellent source of new resistance genes against late blight. In recent work, they report resistance gene Rpi-amr1 and its many variants.  Despite varying in sequence by up to 10%, each Rpi-amr1 variant enables the plant to detect the same virulence proteins of late blight, affording protection from disease.

Late blight strains carry two related virulence proteins that are both recognized by most of the Rpi-amr1 variants. This is important because pathogens overcome resistance by losing or substantially modifying their virulence proteins through evolution. The chances of losing or modifying several virulence proteins at the same time is lower.  Rpi-amr1 confers resistance against all of the 19 blight strains tested.

The Rpi-amr1 resistance gene is being combined with two other resistance genes, Rpi-amr3 and Rpi-vnt1, in the commercial potato Maris Piper. The resulting potato lines are immune to a very wide diversity of blight races. This ongoing work is being supported in a BBSRC Super Follow-on Funded grant (see previous TSL news item).

This work would not have been possible without the added value that collaboration creates. Professor Jones worked closely with Professor Sophien Kamoun, also at The Sainsbury Laboratory, Professor Vivianne Vleeshouwers from Wageningen University and others from the John Innes Centre, the Technical University of Munich, and the Universities of East Anglia, Leeds and Hull.

Professor Jonathan Jones said “I’m delighted to see this important work out in print. It took a long time and there were many false leads and confusing data to make sense of, but this Rpi-amr1 gene now looks like one of the best resistance genes in our armoury against late blight. By combining Rpi-amr1 with two other resistance genes, I think it can make a durably blight-resistant potato. I’d like to acknowledge the fantastic and dedicated work of the four lead authors whose persistence was essential.”.

Kamil Witek, one of the lead researchers, said “Solanum americanum is a fantastic and versatile germplasm and we are very pleased with cloning Rpi-amr1. It’s a very strong gene providing resistance against all races of P. infestans we tested so far. It’s been a long, but really fun collaborative project with many great colleagues. I’m looking forward to seeing potatoes protected by S. americanum resistance genes on the supermarket shelves in the near future!”.

This study, “A complex resistance locus in Solanum americanum recognizes a conserved Phytophthora effector”, appears in Nature Plants.

This study was funded by the Biotechnology and Biological Science Research Council and the Gatsby Charitable Foundation.

Kamil Witek, Xiao Lin, Hari S Karki, Florian Jupe, Agnieszka I Witek, Burkhard Steuernagel, Remco Stam, Cock van Oosterhout, Sebastian Fairhead, Robert Heal, Jonathan M Cocker, Shivani Bhanvadia, William Barrett, Chih-Hang Wu, Hiroaki Adachi, Tianqiao Song, Sophien Kamoun, Vivianne GAA Vleeshouwers, Laurence Tomlinson, Brande BH Wulff and Jonathan DG Jones. A complex resistance locus in Solanum americanum recognizes a conserved Phytophthora effector. Nature Plants. 11 February 2021. DOI: 10.1038/s41477-021-00854-9