Hosts and Symptoms
The fungal pathogen Fusarium oxysporum affects a wide variety of hosts of any age. Tomato, tobacco, legumes, cucurbits, sweet potatoes and banana are a few of the most susceptible plants, but it will also infect other herbaceous plants. Fusarium oxysporum generally produces symptoms such as wilting, chlorosis, necrosis, premature leaf drop, browning of the vascular system, stunting, and damping-off. The most important of these is vascular wilt. Fusarium wilt starts out looking like vein clearing on the younger leaves and drooping of the older lower leaves, followed by stunting of the plant, yellowing of the lower leaves, defoliation, marginal necrosis and death of the plant. On older plants, symptoms are more distinct between the blossoming and fruit maturation stages.
Fusarium oxysporum is split into divisions called formae speciales (singular forma specialis, abbreviated f.sp.). There are over 100 formae speciales divisions, each with one or two different races. Each forma specialis within the species are host-specific (i.e. specific to a certain plant) and produce different symptoms:
F. oxysporum f. sp. batatas affects sweet potato. The symptoms include leaf chlorosis, stunting, and leaf drop. It is transmitted through the soil and through vascular wounds in plant material.
F. oxysporum f. sp. cubense causes Panama disease on banana. It is found everywhere bananas are grown in Africa, Asia, Central and South America. It attacks banana plants of all ages and spreads mainly through the soil. It causes wilting and yellowing of the leaves.
F. oxysporum f. sp. lycopersici causes vascular wilt in tomato. The disease starts out as yellowing and drooping on one side of the plant. Leaf wilting, plant stunting, browning of the vascular system, leaf death, and lack of fruit production also occur.
F. oxysporum f. sp. melonis attacks muskmelon and cantaloupe. It causes damping-off in seedlings and causes chlorosis, stuting and wilting in old plants. Necrotic streaks can appear on the stems.
Read more about this topic: Fusarium Wilt
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