| Auricularia polytricha, a kind of edible and medical fungi, is one of the widely cultivated edible fungi in our country. Nevertheless, molecular biology research progress of this species has been slow. System selection, which breeding efficiency is extremely low, is the main method for new varieties breeding. Genetic linkage map construction and QTL mapping study of this species will help to use new methods, such as marker-assisted selection, to select the new varieties of A.polytricha.In this study, a mapping population, including 123 single spore isolates that originated from hybrid strain APM2-16, was used for constructing a genetic linkage map of A.polytricha and analysing QTLs for mycelial growth rate of monokaryon. Based on the preliminary study of RNA-seq and SSR markers development, a total of 733 molecular markers, containing 337 SSR markers, seven pairs of primers for RT-PCR, 373 In Del markers, eight genic markers of laccase(CAPS 、SCAR et. al)and eight pairs of primers for ESTs homologous with mating type genes, were further selected to screen the polymorphisms between APP7 and M2S16. The molecular markers with polymorphism were utilized for population genotyping. Altogether 167 loci were obtained and used for genetic linkage analysis. A total of 160 Intragenic markers, containing 54 In Del loci, 86 SSR loci, eight genic markers of laccase and 12 other loci, were spread over 14 linkage groups(LGs). The map covers 595.7 c M, with an average distance of 4.1 c M between markers. The number of markers per group is varied from two to 20. The length of linkage group ranged from 2.5 to 61.9 c M. The largest interval between two adjacent markers was 22.7 c M on LG2, and three intervals larger than 20 c M was found on the other linkage groups.The estimated genome length was 714.5 c M. The coverage of markers within 10 c M and 5 c M were 99.5% and 93.2%, separately.Based on the current genetic linkage map, three quantitative trait loci(QTLs) controlling mycelial growth rate of monokaryon on the complete yeast medium and sawdust medium were detected by the CIM method. mgr-cym-II for monokaryotic growth rate on complete medium located on LG2, closely linked with In Del markers APD62 /APD103, explained 10.9 % of the phenotypic variation. It has a negative additive effect, which demonstrated that favorable allele came from the parental strain APP7. For monokaryotic growth rate on sawdust medium, QTLs mgr-sd-Ⅹ-1and mgr-sd-Ⅻ-2 were mapped on LG10 and LG12 respectively. The two QTLs explained 21.9 % of the phenotypic variation together. Both favorable alleles at the two loci also came from the parental strain APP7. mgr-sd-Ⅹ-1 on LG10 squarely located on In Del marker PD128, explained 8.1 % of the phenotypic variation. Another QTL related to monokaryotic growth rate on sawdust medium linked to SSR marker APS120 mapped on LG12, explained 13.9 % of the phenotypic variation.This research, constructing a genetic linkage map of A. polytricha based on ESTs molecular marker as well as mapping QTLs controlling vegetative growth rate, made primary groundwork for the further study of mapping important agronomic traits of A.polytricha, function gene cloning, marker-assisted selection and comparative genomics. |
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