Bunashimeji Mushroom Named ‘HKHM25’

BACKGROUND OF THE INVENTION

This invention relates to a new and distinct variety of Bunashimeji mushroom, Hypsizygus marmoreus (Peck) H.E.Bigelow. This new variety named ‘HKHM25’, cultivated by repeated breeding of Bunashimeji mushroom having thick and elastic stems, dark cap color, strong cap roll, and a large mushroom size, has a high quality and enhanced cultivation stability, and ensures presentable stability, reproducibility, and uniformity.

The annual production of Bunashimeji mushrooms is approximately 120,000 tons in 2020, making it the second most consumed edible mushroom after enokitake mushroom in Japan. However, since Bunashimeji mushrooms have become available in large quantities in the market, Bunashimeji mushrooms with improved flavor, quality and shelf life has been pursued, which led to the development of ‘Hokuto 18gokin’ by our company. Further, our company has been conducting a wide variety of studies for the more stable cultivation and better quality of Bunashimeji mushrooms. Our company has developed a ‘marmo22go’ mushroom which is thicker, whiter, and has larger mushroom than ‘Hokuto 18gokin’.

Further, using ‘marmo22go’ as a parent, as a result of continuing breed improvement by cross breeding to improve stability and quality, ‘HKHM25’, which has thicker stems and stronger cap roll, as compared to ‘marmo22go’, was developed, confirming its stability, reproducibility, and uniformity.

SUMMARY OF THE INVENTION

The present invention is a new and distinct variety of mushroom plant characterized particularly by having thick and elastic stems, dark cap color, strong cap roll, and a large mushroom size, which can be cultivated by gathering and repeated breeding of fungal strains having a stability, reproducibility and uniformity when being produced. This novel and distinct variety of mushroom is identified as ‘HKHM25’.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a phylogenetic tree illustrating the antecedents of ‘HKHM25’.

FIGS. 2 A and 2 B respectively show front and back images of a dual-culture of ‘HKHM25’.

FIGS. 3 A and 3 B respectively show front and back images of a dual-culture of ‘HKHM25’ and ‘Hokuto 18gokin’.

FIGS. 4 A and 4 B respectively show front and back images of a dual-culture of ‘HKHM25’ and ‘marmo22go’.

FIGS. 5 A and 5 B respectively show front and back images of a fungal flora of ‘HKHM25’ grown in a petri dish.

FIGS. 6 A and 6 B respectively show front and back image of a fungal flora of ‘Hokuto 18gokin’ grown in a petri dish.

FIGS. 7 A and 7 B respectively show front and back images of fungal flora of ‘marmo22go’ grown in a petri dish.

FIG. 8 shows an image of cultivation area of ‘HKHM25’.

FIG. 9 shows an image of cultivation area of ‘Hokuto 18gokin’.

FIG. 10 shows an image of cultivation area of ‘marmo22go’.

FIG. 11 shows an image of a fruit body of ‘HKHM25’.

FIG. 12 shows an image of a fruit body of ‘Hokuto 18gokin’.

FIG. 13 : shows an image of a fruit body of ‘marmo22go’.

FIG. 14 shows an image of density and surface color of fungal flora in cultured hyphae of ‘HKHM25’.

FIG. 15 shows an image of density and surface color of fungal flora in cultured hyphae of ‘Hokuto 18gokin’.

FIG. 16 shows an image of density and surface color of fungal flora in cultured hyphae of ‘marmo22go’.

FIG. 17 shows an image of development of aerial hypha of ‘HKHM25’.

FIG. 18 shows an image of development of aerial hypha of ‘Hokuto 18gokin’.

FIG. 19 shows an image of development of aerial hypha of ‘marmo22go’.

FIG. 20 shows an image of size and distribution of mottle of ‘HKHM25’.

FIG. 21 shows an image of size and distribution of mottle of ‘Hokuto 18gokin’.

FIG. 22 shows an image of size and distribution of mottle of ‘marmo22go’.

FIG. 23 shows an image of shape and thickness of stipe of ‘HKHM25’.

FIG. 24 shows an image of shape and thickness of stipe of ‘Hokuto 18gokin’.

FIG. 25 shows an image of shape and thickness of stipe of ‘marmo22go’.

DETAILED DESCRIPTION OF THE INVENTION

‘HKHM25’ has been asexually reproduced by tissue culture, at HOKUTO CORPORATION in Japan. The history of the ‘HKHM25’ mushroom in terms of improvement period and the like are set forth in the following chronological list of each stage of variety improvement:

•

• December 2014: Cultivation of ‘MH025615’ strain. • January 2017: Cultivation of ‘M11025617’ (‘marmo22go’) strain. • December 2019: ‘MH025615’ and ‘MH025617’ (‘marmo22go’) strains were crossed and a strain with thick stem, strong cap roll, and good quality among the obtained strains was selected as ‘MH025633’. We then repeated the cultivation test to distinguish the strains. • March 2021: After repeated cultivation tests, since distinguishability, stability, and uniformity were confirmed, the strain was named ‘HKHM25’ and its cultivation was completed. Applied for registration of a new variety to the Ministry of Agriculture, Forestry and Fisheries of Japan.

The above crossing is summarized in the phylogenetic tree illustrated in FIG. 1 .

The ‘HKHM25’ mushroom has the following characteristics: thick and elastic stems, dark cap color, strong cap roll, and overall large size.

(1) Comparison with Existing Variety by Dual Culture

Dual culture was performed for the ‘HKHM25’ mushroom and a similar variety to examine whether or not a zone line is formed.

Study Method:

As an examination method, a potato dextrose agar medium was used, and the ‘HKHM25’ mushroom and the similar variety were inoculated thereon face to face at an interval of 3 cm, and then culture was performed at 25° C. for 28 days to examine whether or not a zone line was formed.

Strains used for the comparison between present variety, ‘HKHM25’ and other varieties:

•

• ‘HKHM25’: Present variety • ‘Hokuto 18gokin’: Variety similar to the present variety • ‘marmo22go’: Parent variety of the present variety Results:

Zone lines were formed between ‘HKHM25’ and all other co-cultured varieties

(TABLE 1, FIGS. 2 to 4)

This clearly shows that the present mushroom is a new variety.

Similar varieties

Hokuto 18gokin marmo22go

HKHM25 + +

+ is present and − is absent.

*Zone line formation was not observed in the dual culture between ‘HKHM25’ strains. (2) Growth Characteristics of ‘HKHM25’ Study Method:

After inoculating an agar piece of the ‘HKHM25’ having a diameter of 5 mm and an agar piece of the similar variety having a diameter of 5 mm on a potato dextrose agar medium, preculture was performed at 25° C. for 4 days so as to make the regeneration of hyphae equal (about 10 mm in diameter), and then culture was performed for 7 days at intervals of 5° C. between 5° C. and 30° C. An average daily hyphae growth rate was calculated based on a hyphae growth rate for 7 days of the culture. Also, the optimum culture period for ‘HKHM25’ is 80 days, and the number of growing days at that time is 23.1 days.

Results:

‘HKHM25’ had the fastest average daily hyphae growth rate at 20° C. In addition, HKHM25 had slower mycelial growth rate than ‘Hokuto 18gokin’ and ‘marmo22go’ at each temperature zone (Table 2).

(3) Morphological Characteristics of the ‘HKHM25’ Mushroom in a Cultivation Example

Cultivation Method:

Container: An 850 polypropylene bottle (Capacity: 850 ml, diameter 58 mm) was used.

Culture medium: Conifer sawdust, corn cob, rice bran and wheat bran were mixed at the dry weight ratio of 7:3:8:2, and the water content was adjusted to 65%. The culture medium was filled up to the brim of the bottle at the rate of 540±20 g per bottle, and was sterilized at high pressure.

Starter culture: About 20 ml of sawdust starter cultures per bottle was inoculated.

Culture: Culture was performed at 22° C. for 50 to 90 days at 70% moisture.

Growth: After completing the culture, the inoculum is removed, and shifted to a growing room. Development was conducted under a temperature of 15±1° C., at humidity of 95% or about 2,000 ppm CO 2 density. Also, light was not particularly irradiated until the first 14th day, then irradiated with about 500 to 1,000 Lx. The mushroom is harvested when the cap in the center of the stump has sufficiently opened.

Cultivation Results:

Table 2 shows the characteristics of the ‘HKHM25’ and specific difference in characteristics as compared with the similar variety when culture was performed under the abovementioned conditions.

In addition, according to R.H.S. Colour Chart, the color of the central part of cap: 199A, the color of the peripheral area of cap: 199C, the color of gill: 158C, the color of stripe: 155B. All color references are from The R.H.S. Colour Chart of The Royal Horticultural Society of London (R.H.S.), fifth edition published in 2007. Also, the descriptions are from mushrooms that are on the 24 th day.

TABLE 2

Fungus characteristics Table of Hypsizygus marmoreus (Peck) H.E. Bigelow of Recording and Registration

(Please circle the applicable items for the characteristics.)

Characteristic

values

Remarks of similar

Characteristic values of present variety (comparison (Measured varieties

with standard varieties values, (Hokuto

Character 01 02 03 04 05 06 07 08 09 etc.) (marmo22go) 18gokin)

Physio-

logical

property

Dual

culture

Zone line none ob- — 09 09

formation served

Dislike- none ob- — 01 01

touch served

reaction

Density of cultured hyphae low medium 03 02 02

Develop- ment of aerial low medium 03 03 02

hypha

Color of surface of fungal flora white pale yellow other 02 01 01

Color of back of fungal flora white pale yellow other 02 02 02

Accommo-

dativeness

for

temperature

Optimal temperature for hyphal growth 24~ 26° C. 28~ 30° C. 03 21.9° C. 05 24.1° C. 04 22.5° C.

Hyphal growth rate 5° C./mm low high 05 0.52 mm 06 0.70 mm 05 0.56 mm

Hyphal

growth

rate

10° C./mm low medium 04 0.86 mm 05 1.16 mm 05 1.24 mm

15° C./mm low high 05 1.65 mm 05 1.95 mm 05 1.80 mm

20° C./mm low medium high 04 2.47 mm 05 2.79 mm 05 2.60 mm

25° C./mm low medium high 04 2.01 mm 05 3.29 mm 04 2.47 mm

30° C./mm low medium high 04 0.91 mm 07 2.17 mm 05 1.23 mm

Morpho-

logical

property

Cap

Cross sectional shape convex flat con- cave other 02 02 02

Mottle of the surface few many 02 02 02

Size of mottle small medium 03 01 03

Distribution of mottle whole part 01 02 02

Clarity of mottle unclarity moderate 03 03 03

Size medium large 03 21.2 mm 03 23.2 mm 02 20.4 mm

Color of central area white grey- yellow light grey- brown yellow- brown dark tan dark grey tan dark grey brown other 05 199A 05 199C 05 199B

Color of peripheral area white grey- yellow light grey- brown yellow- brown dark tan dark grey tan dark grey brown other 05 199C 05 199D 05 199D

Thickness thin medium thick 08 9.8 mm 09 11.3 mm 0.7 8.1 mm

Fleshy soft hard 05 05 07

Gill

Color white light orange yellow grey- yellow other 02 158C 02 158C 02 158C

Alignment normal other 02 02 02

Width narrow wide 02 02 02

Density low high 02 02 02

Stipe

Shape long and thin short and thin long and thick short and thick 05 05 01

Length short long 05 56.0 mm 05 53.9 mm 04 52.8 mm

Thickness thin medium thick 09 17.7 mm 08 16.5 mm 05 9.4 mm

Color yellow- white grey grey- brown other 01 155B 01 155B 01 155B

Hair few medium many 01 01 01

Fleshy soft medium 03 02 02

Ratio of maximum diameter of small medium 07 2.24 06 1.91 04 1.52

stem to

diameter

just below

cap

Cultural

property

Develop-

ment of

fruit body

Develop- ment group scattered 03 03 03

Optimal culture period short long 05 80 days 05 80 days 06 90 days

Length of time from fruit body- short long 05 23.3 days 04 21.9 days 05 22.3 days

formation

promotion

to fruit

body

harvesting

Optimal temperature for low medium 07 19° C. 07 19° C. 05 15° C.

primordial

development

Optimal temperature for fruit body low high 05 15° C. 05 15° C. 05 15° C.

growth

Adaptivity for

illuminance

Adaptivity for

culture

Yield

Yield of fruit body few many 05 125.4 g 06 137.0 g 02 98.4 g

The number of productive few medium many 02 19.4 stems 03 21.7 stems 03 23.6 stems

stems

Other

property

Bitter none weak strong

ingredient

Disease

resistance

Ingredients

Notes:

Circle shows the characteristics of ‘HKHM25’. The R.H.S. Colour Chart of The Royal Horticultural Society of London (R.H.S.), fifth edition published in 2007, The R.H.S. contact: R.H.S. Membership Department The Royal Horticultural Society PO Box 313 London, SW1P 2PE