β-(1,3) glucanase activity and quantity of fungus in relation to Fusarium wilt in resistant and susceptible near-isogenic lines of muskmelon

β-(1,3)-Glucanase activity and the growth of Fusarium oxysporum f. sp. melonis in near-isogenic lines of resistant and susceptible muskmelon were studied. The activity of the enzyme increased in response to infection. However, in both hypocotyls and roots, the increase was greater (approx. 2 times) in the resistant (Hemed) seedlings than in the susceptible (On) ones. The activity was initiated by the infection process or could be induced by pretreatment with laminarin. Fungal colonization, as determined by chitin content, was correlated with the disease reaction in the cultivars tested. It was concluded that the increase in activity of the host β-(1,3)-glucanase in the resistant cultivar provides a potential defence mechanism against F. oxysporum f. sp. melonis induced wilt.