CropsBiology, epidemiology
Rhizopus stolonifer has biological characteristics comparable to those of other fungi found on grape berries. It often lives in the saprophytic state on the vine and in its environment, becoming an opportunistic pathogen when the physiological state of the berries is modified (presence of wounds, advanced maturity ...).
- Storage and sources of inoculum
This mucoral, saprophyte par excellence and very ubiquitous, is present on numerous plant debris on and in the soil, and on various senescent fruits. It causes damage to many plants: several Cucurbitaceae, eggplant, tomato, broad bean, sweet potato, various fruit trees (apricot, peach, plum, etc.), corn, etc.
- Plant penetration and host invasion
This fungus penetrates berries mainly when ripe, in particular by:
- contact of rotten berry to healthy berry;
- the intermediary of the stomata, lenticels and microcracks, various injuries such as damage linked to pathogenic insects or fungi, physiological micro-bursts, bird pecks or solar burns.
Subsequently, its mycelium develops very extensively, growing in all directions inside the flesh which gradually decomposes thanks to the action of various enzymes (pectinases, amylases).
- contact of rotten berry to healthy berry;
- the intermediary of the stomata, lenticels and microcracks, various injuries such as damage linked to pathogenic insects or fungi, physiological micro-bursts, bird pecks or solar burns.
Subsequently, its mycelium develops very extensively, growing in all directions inside the flesh which gradually decomposes thanks to the action of various enzymes (pectinases, amylases).
- Sporulation and dissemination of the fungus
R. stolonifer , which evolves rapidly in berries, soon sporulates in the form of numerous sporangiophores harboring innumerable black spores in spore vesicles (figure 1). These are spread by the wind over long distances and by splashing water and some insects. It should be noted, as for Botrytis cinerea , that the transmission of rotten berries to healthy berries is very frequent on clusters.
- Factors influencing the development of fungus
It grows rapidly and sporulates abundantly in the presence of humidity and when temperatures are mild. Its thermal development optimum is between 23 and 28 ° C.
Figure 1