EFFECTS OF FUNGAL INFECTION AND WOUNDING ON THE EXPRESSION OF CHITINASES AND BETA-1,3 GLUCANASES IN NEAR-ISOGENIC LINES OF BARLEY

Chitinases (EC 3.2.1.14) and beta-1,3 glucanases (EC 3.2.1.39) have been known to play a vital role in the defense of plants against fungal pathogens. The pattern of induction of these two enzymes subsequent to infection by powdery mildew was studied in 10 pairs of near-isogenic lines of barley (Hordeum vulgare L.) which possess powdery mildew resistance genes. These isogenic lines have been grouped according to their reaction to the fungus. The induction patterns varied between the resistant and the susceptible cultivars within each group and between different groups. More isozymes were induced in susceptible varieties of highly resistant groups and the overall levels and the number of isozymes of chitinases and beta-1,3 glucanases were lower in groups with low resistance. The effect of powdery mildew infection and mechanical wounding on the cellular localization of chitinases and beta-1,3 glucanases in barley leaves has also been studied. The 31 kDa leaf chitinase, LCH2, and trace amounts of a 25 kDa chitinase, L-CH3, were present in healthy leaves. Wounding increased the levels of L-CH3 within 16 h. Powdery mildew infection increased the levels of L-CH3 both in intercellular fluid and in intracellular extract of leaves. A beta-1,3 glucanase, GL-1, also increased after infection and wounding. In infected barley leaves, GL-1 was present both in intercellular space and intracellular extract. It is concluded that powdery mildew resistance genes exhibit qualitative and quantitative differences in the expression of chitinases and beta-1,3 glucanases. Further, chitinases and beta-1,3 glucanases appear to be a response to active infection rather than the factors responsible for disease resistance.