Crops
Berkeleyomyces basicola (Berk. & Broome) W.J. Nel, Z.W. de Beer, T.A. Duong & M.J. Wingf.
Black root rot
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General
- Fungus rather known by the synonyms of Chalara elegans Nag Raj & WB Kendr., Thielaviopsis basicola (Berk. & Broome) Ferraris.
- Present in many countries of the world and rather polyphagous, attacking more than 120 plant species belonging to at least 15 different botanical families.
- Among the vegetable crops are beans, peas, cucumber, melon, watermelon, carrot, lettuce and endive, eggplant, tomato ...
- Exceptionally reported on eggplant, its damage on eggplant in France is anedoctic. Sometimes observed at the same time as attacks of Phytophthora parasitica .
- Organs attacked : reduced portions of roots mainly in soil.
- Symptoms :
- Lesions on roots of limited extension, wet, brown to black, sometimes superficially suberized. They are present in low numbers on the main roots.
- Usually there is no more or less reversible secondary leaf wilting.
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- Signs : presence of arthroconidia (chlamydospores) on and in altered root tissues (figures).
- Confusions possibles : Rhizoctonia solani , Oomycètes ( Pythium et Phytophthora spp.)
Biology
- Storage : keeps for a very long time in the soil thanks to its chlamydospores (figure). It is able to colonize organic matter and infect many host plants, whether cultivated or not, which will help to multiply and conserve it. These hosts do not have the same sensitivity to this fungus and therefore multiply it more or less well.
In nurseries, dust from contaminated soil is an important source of inoculum. It is also preserved on the material used for the production of the plants. - Inoculum sources : the chlamydospores, to a lesser extent the endoconidia (Figure 2), germinate near the roots.
- Infection : The mycelium enters the root tissues either directly through the epidermis or through wounds.
- Development, sporulation : it rapidly colonizes the tissues of the cortex and the vessels that it causes to rot. In damaged tissues, it produces numerous chlamydospores. It also forms on the surface of the roots, along with a multitude of endoconidia.
- Dissemination : Chlamydospores and endoconidia are easily disseminated by water and soil dust. It is likely that the soil, present on the tools used to work the soil, contributes to the propagation. The same is true for vegetable plants and other contaminated cultivated plants.
- Favorable conditions : attacks plants in difficult growing conditions, for example during cold and wet springs, conditions which limit the root development of plants. It therefore appreciates wet soils, but especially cold. Its thermal optimum is normally around 17-23 ° C. The soil's pH influences its behavior; at acidic pH (around 5.6) it is normally less active. The supply of calcium in the soil can increase its parasitism.
Protection
- This parasitic fungus does not normally require the installation of special protection.
- Carry out fairly long crop rotations in virgin land, they will only be very partially effective in contaminated soil.
- Disinfection of the soil possible, but without real interest on eggplant culture.
- Use healthy substrates and plants.
- Eliminate root systems affected during and at the end of cultivation, as well as potential host weeds likely to harbor or promote the development and conservation of this fungus in the soil.
- Clean tools used for tillage from contaminated plots before being used in other healthy plots. It is the same for the wheels of tractors. Thorough rinsing with water and disinfection of this material will often be sufficient to rid it of contaminating soil and propagules of the fungus.
- Take care of the drainage of the cultivated plot, the irrigation (optimal quantity, localized supply), maintain the pH of the soil around 6 and do not over-lime it. Beware of certain organic matter brought to the ground.
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