European Journal of Plant Pathology

, Volume 109, Issue 5, pp 471-478

First online:

Evidence that a Leaf-Disk Test Allows Assessment of Isolate-Specific Resistance in Brassica oleracea Crops Against Downy Mildew (Peronospora parasitica)

  • Bérénice AgnolaAffiliated withBretagne Biotechnologie Végétale, Penn ar Prat
  • , Stéphane BouryAffiliated withBretagne Biotechnologie Végétale, Penn ar Prat Email author 
  • , Claudie MonotAffiliated withBretagne Biotechnologie Végétale, Penn ar Prat
  • , Anne QuillévéréAffiliated withBretagne Biotechnologie Végétale, Penn ar Prat
  • , Yves HervéAffiliated withBretagne Biotechnologie Végétale, Penn ar Prat
  • , Drissa SiluéAffiliated withBretagne Biotechnologie Végétale, Penn ar Prat

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A rapid resistance/susceptibility test for Peronospora parasitica (downy mildew) was established by inoculating leaf-disks of four Brassica oleracea accessions. Several conditions were tested: disk disinfection or not, agar medium with or without nutrients and with 50 or 100 ppm of benzimidazole. Using disinfected disks placed on agar (no nutrient and benzimidazole at 50 or 100 ppm), the responses of leaf-disks to four isolates were similar to those obtained using the classical cotyledon test, whereas undesired contaminations occurred in all other conditions. The possible effect of the particular leaf used for obtaining the disks was also studied. In each incompatible interaction tested, disks were resistant whatever the leaf used. In compatible interactions, susceptible phenotypes were observed on disks derived from the six lowest leaves, but disks from upper leaves were resistant. The genetic basis of resistance in a F1 hybrid broccoli was assessed, by testing six isolates on an F2 population derived from this hybrid. The cotyledon test only allows inoculation of two isolates per seedling, whereas many isolates can be tested on each plant by using leaf-disks. The segregation of the resistance to each of the six isolates was analysed: two dominant genes (tightly linked) control resistance to all isolates (one to five isolates; the other to only one isolate).

Brassica vegetable crops disease resistance gene downy mildew in vitro test