Before developing on the crown of the tomato, Fusarium oxysporum f. sp. radicis-lycopersici (FORL) more or less completely colonizes the roots , on which it causes numerous brown lesions as well as their rot ( Fusarium crownand root rot ). Subsequently, it reaches the base of the stem on which a brown, wet and well-defined lesion gradually develops (Figure 1). This is slightly depressed and can extend over several tens of centimeters (figure 2). It should be noted that the chancre at the neck elongates in a point upwards, giving the lesion the shape of a flame.

Vascular tissues are also affected: they turn brown at the level of the roots, in the taproot but also over several centimeters above the foot of the plant (figures 3 and 4).

Cankers may be partially covered with a characteristic salmon-pink mucus (Figure 5). This consists of numerous sporodochia producing innumerable micro- and macroconidia, Fusarium often multicellular and arcuate.

It is obvious that in the presence of such symptoms the plants can wilt and even die off completely.

Note that there are resistant varieties and rootstocks. The systematic use in greenhouses of resistant varieties has considerably reduced the incidence of this fungus.

Another Fusarium , F. solani , is reported to be responsible for crown rots on vegetable solanaceae (eggplant, pepper, tomato), mainly under tropical production conditions. It produces, on altered tissues, its conidial shape and its teleomorph (red perithecia) ( Haematonectria haematococca [Berk. & Broome] Samuels & Rossman [1999]).

It seems to be rife in association with other pests and / or plants which have otherwise undergone water stress.

For additional information on this fungus, you can consult the Fusarium oxysporum f. sp. radicis-lycopersici .