School of Agriculture, Ludong University, Yantai, Shandong, China.
Research Institute of Subtropical Forestry, Chinese Academy of Forestry, Hangzhou, Zhejiang, China.
PeerJ. 2024 Jul 9;12:e17648. doi: 10.7717/peerj.17648. eCollection 2024.
The rapid degeneration of strains during subculture represents a bottleneck problem that affects production stability. This study explored the mechanism underlying this degeneration in three production and three wild-type strains of , isolating single-conidium strains from each. The effects of subculturing on fructification in both original and single mating-type strains were compared. Changes in the ratio of the two mating types were analyzed in both original and degenerated strains. Based on these findings, the two mating strains were paired in different ratios to determine their effects on fruiting. The resulting five strains were heterokaryotic strains with both MAT1-1 and MAT1-2 mating-type genes. Strain jb-2 was a single mating type (MAT1-1) mutant strain that produced stable fruiting bodies but failed to produce ascospores. It was found that the loss of or imbalance in mating types was the main reason for the rapid degeneration of fruiting traits during subculture and that this occurred randomly in the MAT1-1 and MAT1-2 types. The strains differed significantly in their stability during subculture. Fruiting was stable in the single mating-type Jb-2 strain, and the eleventh-generation fruited normally. There were differences in yield between the production and wild strains after inoculation with spawn containing different proportions of mating types. The production strain was more stable when inoculated with strains with mating-type ratios of 1:9 to 9:1 without affecting the yield. However, the yield of the wild-type strain xf-1 was positively correlated with the proportion of the MAT1-2 type, while the other two strains showed no correlations. Subculturing single mating-type mycelia separately and mixing them before production effectively mitigated degeneration during subculture. For breeding, selecting strains containing both mating types, which are insensitive to the proportion of mating-type genes, enhanced stability in subculture and reduced the risk of mating-type loss. Direct breeding of specific single-mating type strains to induce fruiting is thus an effective breeding strategy.
菌株在继代培养过程中的快速退化是影响生产稳定性的瓶颈问题。本研究从三个生产菌株和三个野生型菌株中分离出单孢菌株，探索了这种退化的机制。比较了原始和单交配型菌株继代培养对结实的影响。分析了原始和退化菌株中两种交配型比例的变化。根据这些发现，将两种交配型菌株以不同的比例配对，以确定它们对结实的影响。由此产生的五个菌株是具有 MAT1-1 和 MAT1-2 交配型基因的异核菌株。菌株 jb-2 是一种单交配型（MAT1-1）突变株，能稳定产生结实体，但不能产生子囊孢子。结果表明，交配型的丧失或失衡是继代培养过程中快速退化的主要原因，这种情况在 MAT1-1 和 MAT1-2 类型中是随机发生的。菌株在继代培养过程中的稳定性差异显著。单交配型 Jb-2 菌株的结实稳定，第 11 代正常结实。接种含有不同交配型比例的孢子后，生产菌株和野生菌株的产量存在差异。当接种具有 1:9 至 9:1 的交配型比例的菌株时，生产菌株更稳定，而不影响产量。然而，野生型菌株 xf-1 的产量与 MAT1-2 型的比例呈正相关，而另外两个菌株则没有相关性。单独继代培养单交配型菌丝，然后在生产前混合，可以有效缓解继代培养过程中的退化。对于育种，选择同时含有两种交配型且对交配型基因比例不敏感的菌株，可以提高继代培养的稳定性，降低交配型丢失的风险。直接对特定的单交配型菌株进行选育以诱导结实，是一种有效的选育策略。
