Life cycle of Botrytis cinerea

Botrytis cinerea likely survives through the winter in the sclerotial stage. Fungal mycelium can also sometimes overwinter in woody stem tissue. New infections begin in the spring when weather is still fairly cool, but humidity bgeins to rise. The sclerotia germinate in the spring, producing mycelium. This mycelium continues to grow and produces conidiophores which contain conidia, the asexual spores of Botrytis. 

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Once conditions for infection are appropriate, and one of the conidium has landed on a viable host, the conidium germinates then penetrates and invades the host tissue. Penetration occurs directly through the surface of the organ via the appressoirum and with cutin degrading enzymes. After penetrating the cuticle, haustorium grow in the intercell space and exude cutinases and pectinase to breakdown cellular tissues.

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Once the tissue of the host is invaded, Botrytis degrades cellular material so that it can absorb nutrients from the host plant. The invaded tissue becomes soft and has a wet appearance. Once the fungus is established, it begins to porduce conidiophores and conidia, which give the recognizable Gray Mold appearance. These conidia can then reinfect more host tissue.

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At the end of its life cycle, Botrytis begins to produce sclerotia. Sclerotia are more equipped to sruvive the winter than conidia, as they are more hardened due to the presence of melanin. The sclerotia contains hyphal threads that germinate once environmental conditions are favorable. 

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