Crops
Fusarium oxysporum f. sp. root-lycopersici
(Fusarium root blight, FORL)
Fusarium oxysporum f. sp. radicis-lycopersici (FORL) , now present in many countries, is able to attack the roots and crown of tomatoes ( Fusarium crown and root rot ) both in field crops and under cover. It was introduced in the south of France during the 1980s from contaminated horticultural substrates and then quickly spread to all production areas. Before the arrival of resistant varieties in our country, it posed a terrible threat to crops under cover, especially grown in soilless. Since then, it has been in sharp decline.
This devastating fungus is above all subservient to the tomato root system (figure 1) on which it initially causes localized lesions on the brown to brown cortex . Subsequently, these expand while others appear. Eventually, the roots turn brown almost completely, rot more or less and decompose. In addition to the cortex, which is particularly affected, the xylem can turn brown: a longitudinal cut of the taproot and a few large roots shows this.
This vascular browning then spreads to the vessels of the stem (Figure 2), not all of which are affected. Often, a brown streak, a few millimeters wide, extends in the stem for several centimeters. Subsequently, browning affects a larger portion of the stem vessels and can be observed up to more than 30 cm above the soil or substrate.
When the disease is fairly advanced, a moist and brown lesion, slightly depressed and well demarcated, appears on the portion of the stem located at the level of the substrate or the soil. This canker has a particular configuration when it surrounds the neck: its greater development on one side of the stem gives it the shape of a flame. It may be covered by a pale salmon pink mucus formed by the numerous sporodochia formed by F. oxysporum f. sp. radicis-lycopersici , on damaged tissue (Figure 3).
The structures to detect them on and in the roots are characterized by phialides, conidia and chlamydospores on and in the cells of the cortex (unreliable).
In very humid conditions, the cortical tissues of the bottom of the stem, completely rotten, become detached locally.
Of course, these various alterations more or less quickly lead to wilting (reversible at first) of the leaflets and leaves of the apex and / or a yellowing of the leaves at the base of the plants. These leaf symptoms often occur as harvest approaches, on hot days, and when the plants are starting to be loaded with fruit.
Other symptoms can be seen in the chapter on Miscellaneous Collar Alterations .
For additional information on this fungus, you can consult the Fusarium oxysporum f. sp. radicis-lycopersici .
This devastating fungus is above all subservient to the tomato root system (figure 1) on which it initially causes localized lesions on the brown to brown cortex . Subsequently, these expand while others appear. Eventually, the roots turn brown almost completely, rot more or less and decompose. In addition to the cortex, which is particularly affected, the xylem can turn brown: a longitudinal cut of the taproot and a few large roots shows this.
This vascular browning then spreads to the vessels of the stem (Figure 2), not all of which are affected. Often, a brown streak, a few millimeters wide, extends in the stem for several centimeters. Subsequently, browning affects a larger portion of the stem vessels and can be observed up to more than 30 cm above the soil or substrate.
When the disease is fairly advanced, a moist and brown lesion, slightly depressed and well demarcated, appears on the portion of the stem located at the level of the substrate or the soil. This canker has a particular configuration when it surrounds the neck: its greater development on one side of the stem gives it the shape of a flame. It may be covered by a pale salmon pink mucus formed by the numerous sporodochia formed by F. oxysporum f. sp. radicis-lycopersici , on damaged tissue (Figure 3).
The structures to detect them on and in the roots are characterized by phialides, conidia and chlamydospores on and in the cells of the cortex (unreliable).
In very humid conditions, the cortical tissues of the bottom of the stem, completely rotten, become detached locally.
Of course, these various alterations more or less quickly lead to wilting (reversible at first) of the leaflets and leaves of the apex and / or a yellowing of the leaves at the base of the plants. These leaf symptoms often occur as harvest approaches, on hot days, and when the plants are starting to be loaded with fruit.
Other symptoms can be seen in the chapter on Miscellaneous Collar Alterations .
For additional information on this fungus, you can consult the Fusarium oxysporum f. sp. radicis-lycopersici .
Figure 1
Figure 2
Figure 3