Integration of pest resistance gene marking into cereal VCUS studies as a complement to phenotyping

The CASDAR research project CAP PHENOGEN (2020-2023), led by GEVES, in partnership with Arvalis, UFS and INRAE, will enable better characterisation of varietal resistance using resistance gene marking from the 1st year of VCUS studies in addition to phenotyping in the field.

This implementation for registration in the French Catalogue is already implemented for soft wheat eyespot and will be effective from the CTPS 2023-24 campaign for several other pairs: 2 wheat mosaics (SBCMV and WSSMV), barley JNO, and barley Y2 mosaic. The 6th pair, the barley BaYMV Y1 mosaic, will only be tested by marking due to the impossibility of phenotyping the Y1 virus in the field in France.

CTPS decision rules were established for each pair in which phenotyping took precedence over marking. This study demonstrated that marking in the 1st year of study, combined with phenotyping tests in year 1, provides an advantage for registration, by:

• reducing the number of trials or varieties to be established in the field in the 2nd year of study: a cultivar showing a resistant phenotype in year 1 combined with the presence of the target allele conferring resistance will be considered resistant from the first year.
• not discriminating against resistant varieties that may have other sources of resistance. These varieties could, depending on their expertise, undergo a 2nd year of phenotyping to confirm their resistance. In this way, the planned system takes into account the diversity of resistance genes selected, beyond those tested routinely, so as not to hinder the genetic diversity of resistance sources, which is the key to their sustainability.
• Supporting the phenotyping of resistant varieties,
• Without increasing the cost of VCUS studies.