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 be en 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 resi stance genes. These isogenic lines have been grouped according to thei r reaction to the fungus. The induction patterns varied between the re sistant and the susceptible cultivars within each group and between di fferent groups. More isozymes were induced in susceptible varieties of highly resistant groups and the overall levels and the number of isoz ymes of chitinases and beta-1,3 glucanases were lower in groups with l ow resistance. The effect of powdery mildew infection and mechanical w ounding on the cellular localization of chitinases and beta-1,3 glucan ases 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 i n healthy leaves. Wounding increased the levels of L-CH3 within 16 h. Powdery mildew infection increased the levels of L-CH3 both in interce llular fluid and in intracellular extract of leaves. A beta-1,3 glucan ase, GL-1, also increased after infection and wounding. In infected ba rley leaves, GL-1 was present both in intercellular space and intracel lular extract. It is concluded that powdery mildew resistance genes ex hibit qualitative and quantitative differences in the expression of ch itinases and beta-1,3 glucanases. Further, chitinases and beta-1,3 glu canases appear to be a response to active infection rather than the fa ctors responsible for disease resistance.