1999 Volume 6 Pages 53-60
The lipoxygenase (LOX) activity in susceptible and resistant rice leaves after inoculation with the bacterial pathogen Xanthomonas oryzae pv. oryzae was studied. In the compatible combination, the slight suppression of LOX activity was observed from 24 hours to 36 hours after inoculation. In the incompatible combination, LOX activity began to increase 12 hours after inoculation at the latest. This enhancement was observed up to 36 hours after inoculation. The bacteria inoculated onto the compatible rice propagated rapidly, but those inoculated onto the incompatible rice grew poorly. These results suggested the possibility that LOX was related to the bacterial leaf blight resistance of rice. The LOX activity in the susceptible rice leaves inoculated with the extracellular polysaccharide (EPS) mutant was similar to that in the leaves inoculated with the wild strain. This indicated that EPS scarcely affected the induction or suppression of LOX activity in rice leaves. After inoculation of the hrp mutant, the LOX activity in rice leaves was enhanced in the incompatible combination, but was not suppressed in the compatible combination. This indicated the possibility that some metabolic systems or secretion systems involving the hrp gene were related to the suppression of LOX activity in the compatible combination.