INFLUENCE OF RESISTANT TOBACCO AND TOBACCO CYST NEMATODES ON ROOT INFECTION AND SECONDARY INOCULUM OF FUSARIUM-OXYSPORUM F SP NICOTIANAE

The influence of Fusarium wilt-resistant broadleaf tobacco and Globode ra tabacum tabacum on infection and secondary inoculum production by F usarium oxysporum f. sp. nicotianae was investigated under greenhouse and field microplot conditions. Wilt severity and postharvest F. oxysp orum density in soil was greater for wilt-susceptible than wilt-resist ant tobacco in all experiments. G. t. tabacum increased the number of F. oxysporum colonies recovered per centimeter of root for wilt-suscep tible but not for resistant tobacco after 8 wk. F. oxysporum levels in soil were greater after plant infection by both F. oxysporum and G. t . tabacum than after plant infection by F. oxysporum alone. Wilt-resis tant tobacco supported F. oxysporum densities that were intermediate b etween susceptible tobacco and fallow and significantly greater than f allow only after more than one season of production, regardless of nem atode infection, under both field and greenhouse conditions.