Expression of specific (13)-beta-glucanase genes in leaves of near-isogenic resistant and susceptible barley lines infected with the leaf scald fungus (Rhynchosporium secalis).

摘要

Near-isogenic resistant and susceptible lines of barley were inoculated with a virulent race of the leaf scald pathogen R. secalis. The expression patterns of specific barley (13)-beta-glucan endohydrolase (EC 3.2.1.39) isoenzymes weremonitored. Induction of (13)-beta-glucanase activity occurred 1 day earlier and to higher levels in the resistant backcross BC-200 than in the susceptible parent line. The resistant plants of the backcross line responded more rapidly to pathogen invasion than susceptible lines. The increased (13)-beta-glucanase activity was predominantly attributable to a 2-3 day period in which mRNA transcripts of genes that encode isoenzymes GII and GI accumulated. It is suggested that thesegenes may be important in the defence responses of barley backcross line BC-200 to pathogen attack. A second scald-resistant backcross line, BC-30, developed levels of (13)-beta-glucanase similar to BC-200 upon infection, but max. levels were reached later than in BC-200. The third resistant backcross line, BC-35, showed the same pattern of expression as the susceptible parent cultivar, Clipper. The differences in expression of (13)-beta-glucanase between the resistant backcross lines show that there are physiologically distinct modes of resistance to the scald fungus in barley and that one of these at least is accompanied by (13)-beta-glucanase induction.