INTERACTION OF POPULATION-LEVELS OF FUSARIUM-OXYSPORUM FSP VASINFECTUM AND MELOIDOGYNE-INCOGNITA ON COTTON

Abstract

In autoclaved greenhouse soil without F. oxysporum f. sp. vasinfectum, M. incognita did not cause leaf or vascular discoloration of 59 day old cotton [Gossypium hirsutum] plants. Plants had root galls with as few as 50 Meloidogyne larvae per plant. Root galling was directly proportional to the initial nematode population level. Fusarium wilt symptoms occurred without nematodes with 77,000 fungus propagules or more per gram of soil. As few as 50 Meloidogyne larvae accompanying 650 fungus propagules caused Fusarium wilt. With few exception, leaf symptoms apppeared sooner as numbers of either or both organisms increased. In soils infested with both organisms, the extent of fungal invasion and colonization was well correlated with the extent of nematode galling and other indications of the Fusarium wilt syndrome.