Abstract:
The present variety of mushroom plant named ‘Hokuto Shiro Ichigoukin’ was produced by crossbreeding mutant fungal strains of two parent varieties, a + variety ‘Hokuto Hachigoukin’ and a − variety ‘Hokuto Jyunigoukin,’ after UV irradiation. This edible mushroom is not bitter, and can be cultivated anywhere a cultivation facility can be arranged.

Description:
Latin name of the genus and species of plant claimed:  Hypsizygus marumoreus.    
   The present plant patent application claims priority of Japanese plant variety application No. 14858, filed Jul. 23, 2002, which is hereby incorporated by reference. 
   ‘Hokuto Shiro Ichigoukin’ is a variety of Bunashimeji mushroom plant that was produced by improving the existing varieties to have the following properties: nice white color, no bitter taste, delicious taste with a higher saccharide content, and cultivatable under similar conditions, including cultivation cycle. The scientific name of the variety is  Hypsizygus marumoreus.  The present plant is an edible mushroom. 
   BACKGROUND OF THE INVENTION 
   The present variety ‘Hokuto Shiro Ichigoukin’ was produced using mutant fungal strains of two parent varieties, ‘Hokuto Hachigoukin’ (unpatented) and ‘Hokuto Jyunigoukin’ (unpatented), grown by Hokuto Sangyo Kabushiki Kaisha. Specifically, the + variety was ‘Hokuto Hachigoukin’ and the − variety was ‘Hokuto Jyunigoukin’. ‘Hokuto Hachigoukin’ and ‘Hokuto Jyunigoukin’ were each submitted to UV irradiation, and then the mutated varieties were crossbred to produce the present variety ‘Hokuto Shiro Ichigoukin’. 
   The site of development was on property of Hokuto Sangyo Kabushiki Kaisha Kinoko Sougo Kenkyusho in Nagano, Japan. 
   In April 2000, the mutated ‘Hokuto Hachigoukin’ was produced, in that a UV-irradiated strain was spawned on a culture medium. In August 2000, the mutated ‘Hokuto Hachigoukin’ was harvested, and monospores were isolated. 
   In parallel, in May 2000, the mutated ‘Hokuto Jyunigoukin’ was produced, also in that a UV-irradiated strain was spawned on a culture medium. In October 2000, the mutated ‘Hokuto Jyunigoukin’ was harvested, and monospores were isolated. 
   In September and October 2000, primary hyphae were obtained from mutated ‘Hokuto Hachigoukin’ and mutated ‘Hokuto Jyunigoukin’. From December 2000, mutated ‘Hokuto Hachigoukin’ and mutated ‘Hokuto Jyunigoukin’ were used to obtain crossbred stains. In February 2001, cultivation was started, and harvesting began in May 2001. 
   For cultivation, the cultivated hyphae are typically inoculated in a cultivation medium, like potato dextrose agar (PDA), filled in a sterilized cultivating dish for cultivation and subjected to treatment for growing the mushroom. 
   Further, in June 2001, a cultivation test was started for secondary selection. In October 2001, an HM222 strain, which appeared to be a superior variety, was selected. In December 2001, a cultivation test was initiated for stabilization. 
   In January 2002, a characteristic test was started. In May 2002, after repeated cultivation tests, stability, reproducibility and homogeneity, matching the objectives of improvements, were confirmed, i.e., the asexually propagated clones of the present plant are identical to the original plant in all distinguishing characteristics. Thus the HM222 strain was named ‘Hokuto Shiro Ichigoukin’. 
   SUMMARY OF THE INVENTION 
   The present invention provides a variety, ‘Hokuto Shiro Ichigoukin’, which is an edible mushroom. When this mushroom is cooked in hot water, the bitterness associated with bunashimeji is mostly gone, thus making it a delectable variety. The present variety can be cultivated anywhere a cultivation facility can be arranged. 
   In summary, the morphological characteristics of ‘Hokuto Shiro Ichigoukin’ are as follows: at the appropriate harvesting period, the cap is small and round; the color of the cap center and margin is white; the thickness and quality of the cap meat are medium; the number of mottled spots is medium; the mottled spots are distributed in the central area; the clarity of the mottled spots is medium; the color of the gills is yellowish white; the arrangement of the gills is orderly; the width and density of the gills are medium; the length of the stipe is medium; attachment of the stipe to the cap is centric; the shape of the stipe is moderately thick; the color of the stipe is white; there is no hair on the stipe; and the quality of the stipe meat is medium. 
   As to the cultivation data for ‘Hokuto Shiro Ichigoukin’, yield is about 118.5 g, the number of effective fruit bodies is 62, and the length of time from spawning to harvesting is 91 days. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a photograph showing a front view of the present plant variety cultivated in vases. The test number designation 00HM069 was used before assignment of the variety name; 
       FIG. 2  is a photograph showing a front view of the present variety without growth substrate; 
       FIG. 3  is a photograph showing a perspective view of the present plant variety cultivated in vases; 
       FIGS. 4   a  and  4   b  are photographs showing a surface and a back, respectively, of a culture of the present plant variety. In these figures, the designation MH025220 is the inventor&#39;s company&#39;s internal designation for the stock culture of ‘Hokuto Shiro Ichigoukin’. 
       FIG. 5  is a photograph showing a front view of a parent plant variety, ‘Hokuto Hachigoukin’, cultivated in vases; 
       FIGS. 6A and 6B  are photographs showing a surface and a back, respectively, of cultures of parent plant variety ‘Hokuto Hachigoukin’ (the inventor&#39;s company&#39;s internal designation being MH025019) and of the present invention (designation MH025220), grown in a single dish; 
       FIG. 7  is a photograph showing a front view of a comparison plant variety, ‘Miyuki M-8171’, cultivated in vases; and 
       FIGS. 8A and 8B  are photographs showing a top surface and a back surface, respectively, of cultures of plant varieties ‘Miyuki M-8171’ (the grower company&#39;s internal designation being MH025066) and of the present invention (internal designation MH025220), grown in a single dish.  FIGS. 8A and 8B  show the state in which fungal hyphae of the present invention and a comparison variety, ‘Miyuki M-8171’ confront each other in a single dish. These fungal hyphae doe not commingle, forming a boundary line. This indicates that the two varieties are genetically different from each other. FIG.  8 B is a bottom view of the dish shown in  FIG. 8A  for providing a much better understanding of the boundary line; 
       FIGS. 9A and 9B  are a table and a graph, respectively, showing comparative mycelial growth of the present plant variety, as compared with that of parent plant variety ‘Hokuto Hachigoukin’ and comparison variety ‘Miyuki M-8171’.  FIG. 9A  represents growth rates of the fungal hyphae cultivated in the range of 22° C. to 30° C. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The characteristics of the present variety will be described in comparison with one of the parent varieties. ‘Hokuto Hachigoukin’, and with another corresponding variety, ‘Muyiki M-8171’, which is commercially available (samples were bought at a supermarket in Nagano, Japan). 
   The cultivation site for this comparison was Hokuto Sangyo Kabushiki Kaisha in Nagano, Japan. The cultivation period was January to June 2002. The cultivation was made according to the conventional methods in a facility with a culture room of approximately 60 m 3  in size and a growth room of approximately 30 m 3  in size. In both the culture and growth rooms, an air-conditioning unit, comprising a cooler and heat exchanger, was installed, and in the growth room, cultivation racks and lights were placed. For characteristic analyses, three cultivation tests were performed using 25 bottles per block. The cultivation method used nutrient propagation, and strains were used as seeds. 
   In summary, when compared to ‘Hokuto Hachigoukin’, ‘Hokuto Shiro Ichigoukin’ exhibits the following characteristics: formation of an inhibition zone in dual culture; dense aerial hyphae (‘Hachigoukin’: medium density); cross sectional shape of hat is umbonate (‘Hachigoukin’: umbonate to flat); white cap center (‘Hachigoukin’: yellowish brown); white cap margin (‘Hachigoukin’: light grayish brown); medium quantity of mottled spots (‘Hachigoukin’: many); central distribution of mottled spots (‘Hachigoukin’: all areas except margin); yellowish white colored gills (‘Hachigoukin’: white); and medium length stipe (‘Hachigoukin’: long). 
   When compared to the commercial variety, ‘Hokuto Shiro Ichigoukin’ exhibits the following characteristics: formation of an inhibition zone in dual culture; dense aerial hyphae (commercial variety: medium density); clumped pattern for fruit body development (commercial variety: grouped pattern); central distribution of mottled spots (commercial variety: all areas except margin); yellowish white colored gills (commercial variety: white); a diameter under cap to maximum diameter ratio of 1.59 (commercial variety: 1.6-1.8); and a cap diameter to stripe length ratio of ≧2.1 (commercial variety: 1.5-2.0). 
   In brief the Reference Table below summarizes some of the dimensions of the present invention as compared to the parent varieties, Hokuto Hachigoukin and Hokuto Jyunigoukin, as well as the comparison variety Miyuki M-8171. 
   
     
       
             
           
             
             
             
             
             
           
             
             
             
             
             
           
         
             
                 
             
             
               Reference Table 
             
             
               (Dimensions of typical variety of the invention) 
             
           
        
         
             
                 
               Hokuto Shiro 
               Hokuto 
               Miyuki 
               Hokuto 
             
             
                 
               Ichigoukin 
               Hachigoukin 
               M-8171 
               Jyunigoukin 
             
             
                 
                 
             
           
        
         
             
               Cap Diameter 
               23.2 
               23.4 
               24.9 
               22.5 
             
             
               (mm) d1 
             
             
               Stipe Length 
               49.3 
               56.9 
               41.5 
               55.7 
             
             
               (mm) L 
             
             
               Ratio (L/d1) 
               2.13 
               2.45 
               1.68 
               2.48 
             
             
               Stipe Diameter 
               7.42 
               5.86 
               7.80 
               7.29 
             
             
               just beneath Cap 
             
             
               (mm) 
             
             
               Maximum Stipe 
               11.79 
               9.21 
               13.27 
               9.58 
             
             
               Diameter (mm) 
             
             
               Ratio (d3/d2) 
               1.59 
               1.58 
               1.71 
               1.31 
             
             
               Cap Thickness 
               8.0 
               6.8 
               7.4 
               8.2 
             
             
               (mm) 
             
             
                 
             
           
        
       
     
   
   The relationship between the parental varieties ‘Hokuto Hachigoukin’ and ‘Hokuto Jyunigoukin’ is explained below: ‘Hokuto Hachigoukin’ has a cap (pileus) with a taupe-color center. ‘Hokuto Jyunigoukin’ is deep gray brown in color. The rim portion of the cap of ‘Hokuto Hachigoukin’ is pale gray brown, and that of ‘Hokuto Jyunigoukin’ is gray brown in color. The cap of ‘Hokuto Jyunigoukin’ is deeper in color on the whole in comparison with ‘Hokuto Hachigoukin’. Maculae are distributed over the entire cap of ‘Hokuto Hachigoukin’, but those of ‘Hokuto Jyunigoukin’ are concentrated at the central part of the cap. The stem of ‘Hokuto Hachigoukin’ is white, but that of ‘Hokuto Jyunigoukin’ is somewhat yellowish in color. Thus, these strains can readily be distinguished in the process of cultivating the strains. 
   The characteristics of the present plant variety will now be described in details, with relevant comparisons with varieties ‘Hokuto Hachigoukin’ and ‘Miyuki M-8171’.
     (1) Dual culture   

   The test was done according to the examination standards established for Shirotamogitake ( Hypsizygus ulmarius ). With regard to the inhibition zone, the results were shown in Table 1 below (+: inhibition zone, −: no inhibition zone formation). 
   
     
       
             
           
             
             
             
             
           
         
             
               TABLE 1 
             
           
           
             
                 
             
             
               Inhibition Zone 
             
           
        
         
             
                 
               “Hokuto Shiro 
               “Hokuto 
                 
             
             
               Similar variety 
               Ichigoukin” 
               Hachigoukin” 
               “Miyuki M-8171” 
             
             
                 
             
             
               “Hokuto Shiro 
               − 
               + 
               + 
             
             
               Ichigoukin” 
             
             
                 
             
           
        
       
     
   
   Thus, an inhibition zone was formed between ‘Hokuto Shiro Ichigoukin’ and the comparative varieties ‘Hokuto Hachigoukin’ as well as ‘Miyuki M-8171’, which is the closest variety after ‘Hokuto Hachigoukin’. 
   Photographs of the cultures for the present plant variety and for comparative varieties ‘Hokuto Hachigoukin’ and ‘Miyuki M-8171’ are shown on  FIGS. 4 ,  6  and  8 , respectively.
     (2) Length of culture from spawning to fruit-body-formation promotion   

   The length of culture from spawning to fruit-body-formation promotion was investigated. Again, the test period was January-June 2002. Except for the number of cultivation days, cultivation was done according to the examination standards established for Shirotamogitake ( Hypsizygus ulmarius ). Three lengths of culture were established at 63, 70 and 77 days. The results are summarized in Table 2 below. 
   
     
       
             
           
             
             
             
           
         
             
               TABLE 2 
             
           
           
             
                 
             
             
               Culture Length 
             
           
        
         
             
               Culture length (days) 
               Growth length (days) 
               Yield (g/bottle) 
             
             
                 
             
             
               63 
               20.5 
               128.0 
             
             
               70 
               20.5 
               143.4 
             
             
               77 
               22.0 
               115.8 
             
             
                 
             
           
        
       
     
   
   Based on the results shown in Table 2, the length of culture was set at 70 days because the yield was the highest for this length.
     (3) Optimal budding temperature   

   To determine the optimal budding temperature, cultivation was done for 70 days according to the examination standards established for Shirotamogitake ( Hypsizygus ulmarius ). Three budding temperatures were established as shown in Table 3 below. 
   
     
       
             
           
             
             
             
           
         
             
               TABLE 3 
             
           
           
             
                 
             
             
               Optimal Budding Temperature 
             
           
        
         
             
                 
               Budding temperature (° C.) 
               Budding length (days) 
             
             
                 
                 
             
             
                 
               13˜14 
               6.7 
             
             
                 
               14˜15 
               6.3 
             
             
                 
               15˜16 
               6.9 
             
             
                 
                 
             
           
        
       
     
   
   Based on the results shown in Table 3, the minimal temperature was set at 14-15° C. bacuase the length of budding was the shortest at this temperature.
     (4) Optimal growth temperature   

   The optimal growth temperature was studied through cultivation for 70 days according to the examination standards established for Shirotamogitake ( Hypsizygus ulmarius ). Three growth temperatures were established as shown in Table 4 below. 
   
     
       
             
           
             
             
             
           
         
             
               TABLE 4 
             
           
           
             
                 
             
             
               Growth Temperature 
             
           
        
         
             
               Growth temperature (° C.) 
               Growth length (days) 
               Yield 
             
             
                 
             
             
               13˜14 
               22.1 
               115.6 
             
             
               14˜15 
               21.2 
               121.1 
             
             
               15˜16 
               24.9 
               107.1 
             
             
                 
             
           
        
       
     
   
   Based on the results shown in Table 4, the optimal growth temperature was set at 14-15° C. because the yield was the greatest at this temperature.
     (5) Summary of cultivation characteristics   

   The cultivation characteristics of the present plant variety are shown in Table 5 below. 
                                                       TABLE 5                   Summary of Cultivation Characteristics                “Hokuto Shiro   “Hokuto   “Miyuki M-       Characteristics   Ichigoukin”   Hachigoukin”   8171”                    Length of culture from   70   70   70       spawning to fruit-       body-formation       promotion (days)       Length of time from   21   21   21       fruit-body-formation       promotion to fruit       body harvesting at       optimal temperature       (days)       Optimal budding   14˜15   14˜15   14˜15       temperature (° C.)       Fruit body   Clumped   Clumped   Group       development pattern       Yield (g/bottle)   118.5   117.1   105.1       Number of effective   62   100   79       fruit bodies       Medium compatibility   SAWDUST   SAWDUST   SAWDUST       Tree selectivity   Mixture   Mixture   Mixture       Cap Size (Diameter)   23.2   23.4   24.9       (mm)       Cross sectional shape   UMBONATE   UMBONATE   UMBONATE       Center color   White   Yellowish   White               brown       Margin color   White   Light grayish   White               brown       Meat thickness (cap   8.1   6.8   7.4       depth) (mm)       Meat quality   MEDIUM   MEDIUM   MEDIUM       Mottled spot quantity   Medium   Many   Medium       Mottled spot size   Medium   Medium   Medium       Mottled spot   Central area   All areas   All areas       distribution       except margin   except margin       Mottled spot clarity   Medium   Medium   Medium       Cracking   Absent   Absent   Absent       Gills Color   Yellowish   White   White           white       Arrangement   Orderly   Orderly   Wavy and                   frizzled       Width   Medium   Medium   Medium       Density   Medium   Medium   Medium       Stipe       Length (mm)       Attachment to cap   Centric:   Centric:   Centric:           eccentric   eccentric   eccentric       Shape   Medium thick   Medium thick   Medium thick       Color   White   White   White       Hair   Absent   Absent   Absent       Ratio of maximum   1.59   1.58   1.72       diameter to diameter       just below mushroom       cap       Ratio of length of   2.1   2.45   1.68       mushroom stem to       diameter just below       mushroom cap       Meat quality   MEDIUM   MEDIUM   MEDIUM                    
The color designations are based on the Japan Color Standard for Horticultural Plant (JHS Color Chart). Other evaluations like the words “medium” are based on the standards stipulated by the Agriculture Forestry and Fisheries Ministry of Japan, under which strains may be evaluated with the eye.
     (6) Cultivation characteristic data   
   Detailed cultivation characteristics of the present plant variety are shown in Table 6 below. The color designations are based on the Japan Color Standard for Horticultural Plant (JHS Color Chart). The code numbers mentioned in the column “Code of the similar variety” below are based on color codes stipulated by JIS (Japanese Industrial Standard). Other evaluations like the words “medium” are based on the standards stipulated by the Agriculture Forestry and Fisheries Ministry of Japan, under which strains may be evaluated with the eye. 
   
     
       
             
           
         
             
               TABLE 6 
             
             
                 
             
             
               Detailed Cultivation Characteristics 
             
             
                 
             
           
           
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
               
                 
                           
                   
                       
                       
                   
                 
               
             
             
                 
             
           
        
       
     
   
   In summary, the ‘Hokuto Shiro Ichigoukin’ is white in color and can be discriminated in variety by the boundary line seen when being cultivated in a dish with another different variety. By comparison, wild ‘Bunashimeji Shirotamogitake’ ( Hypsizygus ulmarius ) is not white. ‘Hokuto Shiro Ichigoukin’ tastes delicious when boiled.