Ultrastructure and Physiological Characterization of Morchella Mitospores and Their Relevance in the Understanding of the Morel Life Cycle

Abstract

Morels, which belong to the Ascomycete genus Morchella, are highly valued edible fungi treasured by gourmet chefs worldwide. Some species are saprotrophic and others are able to form facultative mycorrhizal-like associations with plant roots without establishing true ectomycorrhizal symbioses. In general, it is considered that the formation of asexual spores, or mitospores, is an important step in the life cycle of morels. However, ultrastructure characterization and physiological attributes of morel mitospores have received little attention. In this contribution, the mitospores of M. sextelata were successfully induced under laboratory conditions and their ultrastructure, occurrence, germination, physiological characteristics and mating type gene structure were studied. Mitospore production was closely related to aeration, nutrition and humidity conditions. The average germination rate of mitospores on different media and under various induction stimuli was very low, with an average of 1/100,000. Based on the ultrastructure characterization, low germination rate, growth rate decline, rapid aging and mating genotyping, it was concluded that the mitospores of M. sextelata had lost their conventional function as conidia and might act more as mate sperm-like (gamete) structures. Thus, this study contributed to a deeper understanding of the life cycle of the economically and ecologically important morel fungal group.

Dazomet changes microbial communities and improves morel mushroom yield under continuous cropping

“…The morel was sown on the 35th day after fumigation, and the dosage of spawn was 300 g/m 2 . Seven days after sowing, morel mitospores, which was previously considered as asexual conidia ( Liu et al, 2023 ), appeared on the soil surface. On the 10th day, exogenous nutrient bags punched on the side that would be in contact with the soil were placed on the soil surface.…”

Decline in Morel Production upon Continuous Cropping Is Related to Changes in Soil Mycobiome

“…On day 10, two exogenous nutrition bags (ENBs, containing 330 g substrate [5]) were laid on the soil surface and covered by mulch to maintain the temperature, humidity, and dim sunlight. On day 35, white and powdery conidial mats [12] emerged from the soil surface, and soil samples were collected (referred to as conidial stage samples (CD)). On day 46, the ENBs were removed, and drop watering was applied for at least 12 h to trigger morel fructification.…”

Large-Scale Field Cultivation of Morchella and Relevance of Basic Knowledge for Its Steady Production

“…The results showed that the cell wall of the mitospores of M. sextelata was very thin, which was the thinnest structure during the life cycle of Morchella. Based on the combination of both: (i) A very low germination rate, usually around 1/100,000; and (ii) the rapid aging of the germinating strains, it was presumed that morel mitospores had lost the rapid propagation and reproduction function like conidia and that they behaved more like microspores (spermatium) that played a mating function in fungi [ 60 , 61 ]. However, as a gamete, the time and space of fertilization (mating) are still unknown.…”