Effect of Aging on Culture and Cultivation of the Culinary-Medicinal Mushrooms Morchella importuna and M. sextelata (Ascomycetes)

The prominent problem of "uncertainty" has been frustrating morel farming since the commercial production of Morchella mushrooms was realized in 2012 in China. Spawn aging may be the main underlying reason. In this paper, aging in cultivated strains of M. importuna T4 and M. sextelata T6 was achieved by successive subculturing. Oxidative stress, mycelial growth rate, biomass, sclerotial formation, pigmentation, and yield of different subcultures were determined. The results suggested that M. importuna T4 and M. sextelata T6 exhibited systemic senescence manifested as 24 and 17 subcultures and lifespan of 3048 and 2040 h, respectively. Aging showed a close relevance to oxidative stress. Regression analysis revealed a strong positive correlation between time of subculturing (aging) and lipid peroxidation (oxidative stress) in both morels. In addition, pigmentation tended to increase, while the number of sclerotia tended to decrease, with the rise of subculturing times in both morels. Moreover, the mycelial growth rate and biomass of the last two subcultures were significantly lower than those of others, indicating that cultural characteristics may be used as signs of seriously aging culture. Finally, the yield of subcultures was significantly lower than that of the original strains in artificial cultivation. Regression analysis showed a strong negative correlation between time of subculturing and yield in two morels. This work will improve the understanding of "uncertainty" and thus be beneficial for stable development of morel farming.