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 . 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 ’. 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 ). 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 . 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 . 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 . 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 . 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 . 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 . the cultivation characteristics of the present plant variety are shown in table 5 below . 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 . 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 . 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 .
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 .