Before we try to cultivate morels, or in order to successfully cultivate morels, we need to understand the life cycle of Morchella spp. The first life cycle of Morchella spp. was proposed by Volk and Leonard in 1990. This life cycle is pretty general. It does not confine to any specific Morchella spp. In this life cycle, the primary mycelium, secondary mycelium, the formation of sclerotia, germination of sclerotia and the development of fruiting body is identified.
In 2007, Pilz et. al proposed their life cycle on true morels. Their life cycle is based on Volk and Leonard's life cycle, but their life cycle includes the cellular stages, showing the nuclei status in the hyphae or mycelium. What worth mentioning is that this life cycle also includes some ecological conditions under which this life cycle takes place, such as soil necromass after fire and live tree ectomycorrhizae.
In 2013, Facultad et al. proposed a relatively more complicated and integrated life cycle of Morchella spp. This life cycle integrates all the previous models and experimental observations and research related to this genus.
This life cycle starts with the fruiting body, ascocarp or ascoma. Each ascus produces eight ascospores. Ascospores are released for dispersion. Under certain conditions, ascospore can grow and germinate to form a hypha. These hyphae can continue to grow and form primary mycelium. There are two pathways that the primary mycelium may go through. One is that primary mycelium may produce conidia. The other one is that primary mycelium can continue growing, interwining and develop into a compact masses, which will give rise to sclerotia. The primary mycelium can also fuse with other in a heterothallic way and the secondary mycelium is developed. There can be 15 to 60 nuclei in each septum in the secondary mycelium. The secondary mycelium can also grow repeatedly and interwine to form sclerotia. During this process, the secondary mycelium may form chlamydospores, which are thick-walled and function as resting fungal cells. The imperfect phase is also observed. Under certain stimulus, such as drought, change of temperature, fire and flooding, the sclerotia are able to germinate and give rise to the carpogenic mycelium, which will then develop into fruiting body, the ascocarp.
However, it is not clear that whether the sclerotia produced from the primary mycelium can develop into fruiting bodies directly. And also it is still unknown whether the secondary mycelium is able to develop into a fruiting body or not.