Genetic polymorphism of Mel-21 Morchella tissue isolates

Morel mushrooms are iconic ascomycetes that are economically valuable and have attracted the attention of a large number of scientific researchers around the world. However, the tendency of morel fungi to undergo heterokaryosis through plasmogamy is not well understood. In this study, three populations of stipe tissue isolates were isolated from ascocarps of Mel-21 (Morchella sp.). Mating type gene analysis showed that a large proportion of the mating type idiomorphs were missing in the population. According to the mating type structure, one population could be divided into three categories: isolates containing the only Mat1-1, the only Mat1-2, and both isolated containing both Mat1-1 and Mat1-2 idiomorphs. While random amplified polymorphism DNA (RAPD) molecular markers showed clear polymorphisms among the tissue isolates from the same ascocarp, and there was no consistency between this polymorphism and the mating type structure. The characteristic band of RAPD was further developed into a more specific and stable sequence-characterized amplified region (SCAR) marker to further detect the isolate population, and the results were consistent with the RAPD polymorphism. This study showed that the stipe tissue of Mel-21 morel ascocarp had obvious genetic diversity and was more than two homogenous karyotypes. We speculated that this might be due to the frequent fusion of the hyphae germinated by the genetically diverse ascospores in nature, which eventually led to the heterokaryotic state in the stipe of the ascocarps. This heterokaryotic state should be related to the competition at the nucleus level and/or the heterogeneous distribution of nuclei in the tissue. This genetic polymorphism might be related to the character diversity, ecological environment diversity and rapid species evolution of Morchella.