Cold-induced plant resistance to necrotrophic pathogens and antioxidant enzyme activities and cell membrane permeability

The object of the study was to investigate whether the cold acclimation (5 degreesC for 2-6 weeks) of spring barley (Hordeum vulgare L.), meadow fescue (Festuca pratensis Huds.) and oilseed winter rape (Brassica napus var. oleifera L.) induces resistance to their specific pathogens: Bipolaris sorokiniana or Phoma lingam. An effort was made to correlate changes in the degree of resistance with cell membrane permeability and the catalase (CAT) and superoxide dismutase (SOD) activities. The influence of de-acclimation on the same parameters was also studied. Cold-acclimated plants of each species showed increase resistance to either pathogen. Only in barley was a significant decrease in membrane permeability observed. Changes in antioxidant activity were specific to each species: in cold-acclimated barley and rape the CAT activity decreased, whereas in fescue, activity of Mn-SOD and Cu/Zn-SOD isoforms was stimulated. Cold-induced resistance to B. sorokiniana remained unaffected in barley and fescue during de-acclimation, while the susceptibility of rape to P. lingam returned to control level. Cell membrane permeability and CAT activity were enhanced when barley and rape were dehardened, while in fescue and rape de-acclimation caused an inhibition of Mn-SOD activity. It seems that cold-induced cross-tolerance to fungal pathogens is connected with changes to cell membrane permeability and CAT activity. The resistance of dehardened plants to the fungi was not linked to the parameters studied. (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.