Lentinula edodes (Berk.) Pegler was popular in Southeast Asia not only because of its delicious taste, but also the characteristics of high-protein and low-fat content (Li, et al., 2018). According to the statistics of Chinese Edible Fungi Association (CEFA), the total production in China reached 10.43 million tons in 2018, which was an increase of 82.2% in the last decade. Excellent cultivars are the basis and guarantee for obtaining high-yield and high-quality fruit bodies in cultivation. Breeding is an effective way to obtain excellent varieties. Conventional breeding methods in mushrooms include systematic selection, hybridization, mutation, and protoplast fusion (Ikegaya, 1997). Among them, hybridization through mating with different monokaryons is still the most variety-producing method in breeding of L. edodes (Ha, Kim, & Ro, 2015).As a typical two-factor, tetrapolar basidiomycete, the basidiospores of L. edodes have four different mating types (AxBx, AyBy, AxBy, and AyBx) with two separately mating locus A and B. Before the crossing, single spore isolations of two dikaryotic parental strains were collected and monokaryotic mycelium were germinated by single spore isolations. In breeding, two compatible monokaryons were inoculated closely then the mycelia fused to form the dikaryotic hyphae. Only monokaryons with different locus of mating factor A and B could form the fertile progenies (Brown & Casselton, 2001). If the monokaryons come from only one parent, it is selfing. After the crossing, usually clamp-connection could be easily observed in L. edodes to distinguish the dikaryons with monokaryons (Xiong et al., 2014). The dikaryon strains were screened for excellent hybrid progenies through multiple turns of cultivations. However, the hybrid dikaryon progeny populations were usually large (300-500). And depending on different parents, the breeding progenies no matter selfing or crossing, which mating by compatible single spore isolations, formed normal fruit bodies usually account for 30-70% (Turner, Wright, Ward, Osborne, & Self, 1975). Cultivation and screening are time-consuming and labor-consuming. At present, the whole cultivation cycle of L. edodes was divided into four stages, including vegetative mycelial growth and colonization of the growth substrate, light-induced brown film formation, primordium initiation, and fruiting body development, took at least 4-6 mo (Tang et al., 2013). Formation of normal fruiting bodies was affected by poor growth at any stage. No efficient selection system has been established. If an early screening method
