Effects of mating-type ratio imbalance on the degeneration of Cordyceps militaris subculture and preventative measures.

The rapid degeneration of Cordyceps militaris 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 Cordyceps militaris, 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 Cordyceps militaris 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.

Transcriptome sequencing and de novo analysis for Ma bamboo (Dendrocalamus latiflorus Munro) using the Illumina platform.

BACKGROUND: Bamboo occupies an important phylogenetic node in the grass family with remarkable sizes, woodiness and a striking life history. However, limited genetic research has focused on bamboo partially because of the lack of genomic resources. The advent of high-throughput sequencing technologies enables generation of genomic resources in a short time and at a minimal cost, and therefore provides a turning point for bamboo research. In the present study, we performed de novo transcriptome sequencing for the first time to produce a comprehensive dataset for the Ma bamboo (Dendrocalamus latiflorus Munro). RESULTS: The Ma bamboo transcriptome was sequenced using the Illumina paired-end sequencing technology. We produced 15,138,726 reads and assembled them into 103,354 scaffolds. A total of 68,229 unigenes were identified, among which 46,087 were annotated in the NCBI non-redundant protein database and 28,165 were annotated in the Swiss-Prot database. Of these annotated unigenes, 11,921 and 10,147 unigenes were assigned to gene ontology categories and clusters of orthologous groups, respectively. We could map 45,649 unigenes onto 292 pathways using the Kyoto Encyclopedia of Genes and Genomes Pathway database. The annotated unigenes were compared against Moso bamboo, rice and millet. Unigenes that did not match any of those three sequence datasets are considered to be Ma bamboo unique. We predicted 105 unigenes encoding eight key enzymes involved in lignin biosynthesis. In addition, 621 simple sequence repeats (SSRs) were detected. CONCLUSION: Our data provide the most comprehensive transcriptomic resource currently available for D. latiflorus Munro. Candidate genes potentially involved in growth and development were identified, and those predicted to be unique to Ma bamboo are expected to give a better insight on Ma bamboo gene diversity. Numerous SSRs characterized contributed to marker development. These data constitute a new valuable resource for genomic studies on D. latiflorus Munro and, more generally, bamboo.