Comprehensive Evaluation of Shiitake Strains (Lentinus edodes, Agaricomycetes) Based on Polysaccharide Content and Agronomic Traits.

Polysaccharides are some of the most important bioactive compounds in Lentinus edodes, but little attention has been devoted to the genetic basis of polysaccharide content. Here, the polysaccharide content of fruiting body, and 11 agronomic traits related to morphologic characteristics of fruiting body, yield and precocity of 50 L. edodes strains were screened and analyzed. Results showed that polysaccharide content in L. edodes fruiting bodies is a quantitative trait controlled by the polygenic system. Several wild strains possess desirable polysaccharide contents, exhibiting the potential to improve shiitake cultivars by introducing the promising alleles. There were no close correlations between polysaccharide content and the 11 agronomic traits related with fruiting body morphology, yield and precocity, suggesting that polysaccharide content and the development of fruiting bodies may genetically be controlled independently. Moreover, based on polysaccharide content and the 11 agronomic traits, grey relational analysis (GRA) was employed for a comprehensive strain evaluation by calculating grey relational grades. The results demonstrate that weighted relational grade analysis is effective in the comprehensive evaluation of L. edodes strains. The ranking of most cultivars was higher than that of wild strains. Cultivar ZP9 was the best strain, concerning its comprehensive phenotypic performance. Wild strain YS1 with the highest polysaccharide content (6.60%) also ranked in the top seven. In our study, we developed the first multiple-trait strategy for L. edodes strain evaluation. The step-by-step procedures of GRA described here provide an important reference for strain evaluation and selection of other edible mushrooms.

Detection of Quantitative Trait Loci Underlying Yield-Related Traits in Shiitake Culinary-Medicinal Mushroom, Lentinus edodes (Agaricomycetes).

Increasing yield is a principal goal when breeding Lentinus edodes. The detection of quantitative trait loci (QTLs) underlying yield and its related traits, precocity and the number of fruiting bodies (NFs), is important in order to breed high-yield cultivars. Using composite interval mapping (CIM), we mapped a total of 25 QTLs responsible for precocity, NFs, and yield in 2 segregating populations of L. edodes. QTLs for the 3 traits were mapped on 5 different linkage groups, contributing 5.9% to 15.4% of the phenotypic variation. Colocated QTLs were also found underlying multiple traits, implying the presence of a genic pleiotropic effect or tightly linked genes. This is, to our knowledge, the first report of the genetic dissection of precocity, NFs, and yield using QTL mapping in L. edodes. Findings of this study will facilitate marker-assisted breeding of high-yield cultivars of L. edodes.

Genetic dissection of fruiting body-related traits using quantitative trait loci mapping in Lentinula edodes.

To provide a better understanding of the genetic architecture of fruiting body formation of Lentinula edodes, quantitative trait loci (QTLs) mapping was employed to uncover the loci underlying seven fruiting body-related traits (FBRTs). An improved L. edodes genetic linkage map, comprising 572 markers on 12 linkage groups with a total map length of 983.7 cM, was constructed by integrating 82 genomic sequence-based insertion-deletion (InDel) markers into a previously published map. We then detected a total of 62 QTLs for seven target traits across two segregating testcross populations, with individual QTLs contributing 5.5 %-30.2 % of the phenotypic variation. Fifty-three out of the 62 QTLs were clustered in six QTL hotspots, suggesting the existence of main genomic regions regulating the morphological characteristics of fruiting bodies in L. edodes. A stable QTL hotspot on MLG2, containing QTLs for all investigated traits, was identified in both testcross populations. QTLs for related traits were frequently co-located on the linkage groups, demonstrating the genetic basis for phenotypic correlation of traits. Meta-QTL (mQTL) analysis was performed and identified 16 mQTLs with refined positions and narrow confidence intervals (CIs). Nine genes, including those encoding MAP kinase, blue-light photoreceptor, riboflavin-aldehyde-forming enzyme and cyclopropane-fatty-acyl-phospholipid synthase, and cytochrome P450s, were likely to be candidate genes controlling the shape of fruiting bodies. The study has improved our understanding of the genetic architecture of fruiting body formation in L. edodes. To our knowledge, this is the first genome-wide QTL detection of FBRTs in L. edodes. The improved genetic map, InDel markers and QTL hotspot regions revealed here will assist considerably in the conduct of future genetic and breeding studies of L. edodes.

Constructing a new integrated genetic linkage map and mapping quantitative trait loci for vegetative mycelium growth rate in Lentinula edodes.

The most saturated linkage map for Lentinula edodes to date was constructed based on a monokaryotic population of 146 single spore isolates (SSIs) using sequence-related amplified polymorphism (SRAP), target region amplification polymorphism (TRAP), insertion-deletion (InDel) markers, and the mating-type loci. Five hundred and twenty-four markers were located on 13 linkage groups (LGs). The map spanned a total length of 1006.1 cM, with an average marker spacing of 2.0 cM. Quantitative trait loci (QTLs) mapping was utilized to uncover the loci regulating and controlling the vegetative mycelium growth rate on various synthetic media, and complex medium for commercial cultivation of L. edodes. Two and 13 putative QTLs, identified respectively in the monokaryotic population and two testcross dikaryotic populations, were mapped on seven different LGs. Several vegetative mycelium growth rate-related QTLs uncovered here were clustered on LG4 (Qmgr1, Qdgr1, Qdgr2 and Qdgr9) and LG6 (Qdgr3, Qdgr4 and Qdgr5), implying the presence of main genomic areas responsible for growth rate regulation and control. The QTL hotspot region on LG4 was found to be in close proximity to the region containing the mating-type A (MAT-A) locus. Moreover, Qdgr2 on LG4 was detected on different media, contributing 8.07 %-23.71 % of the phenotypic variation. The present study provides essential information for QTL mapping and marker-assisted selection (MAS) in L. edodes.

Applying target region amplification polymorphism markers for analyzing genetic diversity of Lentinula edodes in China.

The target region amplification polymorphism (TRAP) technique was utilized for assessing the genetic diversity of 55 wild strains and one cultivated strain of Lentinula edodes in China. From these strains, 932 DNA fragments were amplified using 12 primer combinations, 929 fragments (99.68%) of which were polymorphic between two or more strains. The average coefficient of pairwise genetic similarity was 0.696, within a range from 0.503 to 0.947. Cluster analysis and principal coordinate analysis separated the tested strains of L. edodes into two major groups. Group A was further divided into seven subgroups. In most cases, the strains from the same or adjoining regions could be preferentially clustered into small groups. The results from the average genetic similarity and the weighted average value of Shannon's Information Index among the tested strains of L. edodes from the same region revealed a vast genetic diversity in the natural germplasm found in China. Compared with the L. edodes strains from other regions, those found on the Yunnan Plateau, in the Hengduanshan Mountains, in Taiwan, South China, and Northeast China showed greater genetic diversity. The results of the present study indicated that the wild strains of L. edodes in China possessed abundant genetic variation, and the genetic relationships among them were highly associated with the geographic distribution. This is the first report demonstrating that TRAP markers were powerful for analyzing the genetic diversity of L. edodes, and the study lays the foundation for a further application of this remarkable technique to other fungi.