Lipoxygenase (LOX) activity was studied in seedlings of pearl millet genotypes resistant and susceptible to downy mildew pathogen Sclerospora graminicola. An increase in LOX activity was observed during the incompatible host-pathogen interaction whereas the activity decreased in compatible ones. Resistant pearl millet seedlings exhibited a 2.4-fold increase in LOX activity after inoculation with the pathogen. The enzyme activity was maximum at 18 h after inoculation. The enzyme activity was maximum in shoot portion of resistant genotype after inoculation. The enzyme activity correlated well with the degree of host-resistance to the pathogen. Substrate-based gel assay revealed five isozymes (LOX-1, LOX-2, LOX-3, LOX-4 & LOX-5) in both susceptible and resistant genotype. An additional isozyme (LOX-6) was unique to only resistant genotype after inoculation
