Monogenic resistance of sunflower to downy mildew

Monogenic resistance of sunflower to downy mildew

The presence of a breed-specific resistance to downy mildew in a sunflower genotype is shown by a laboratory test. Depending on the breeds of Plasmopara halstedii and the resistance sources, the resistance is caracterised by an absence of sporulation (class R) or a slight sporulation (class RII). This last syndrome is frequently mixed up with a sensitivity presenting a limited sporulation (class SII). The present training program aims at helping you distinguish between plantlets of class SII and RII.

N.B: this training program concerns the recognition of resistance classes in controlled conditions.

Start the training program

The consequences of the errors not being the same, a confusion between categories S and SII (or R and RII) gives you 4 points , while a confusion between sensitive (S or SII) and resistant (R or RII) gives you no point. In all the cases, the right answer gives you 5 points.

The photos used in the training program and the identification of the resistance classes were realised and funded by the units Génétique Diversité et Ecophysiologie des Céréales and Physique et Physiologie Intégratives de l’Arbre Fruitier et Forestier of the INRA centre of Clermont-Ferrand.

Identification of the resistance classes

(Click on the pictures to enlarge them)

Name of the class


Example 1

Example 2


Sporulation on the leaves and the cotyledons


Important sporulation on the cotyledons


Slight sporulation on the cotyledons


Absence of sporulation

Start the training program

Modification date : 25 April 2023 | Publication date : 12 December 2014 | Redactor : Pascal Walser and Denis Tourvieille (INRA)