Ⅲ-4. Radiation Chemistry & Biology

RIKEN Accel. Prog. Rep. 49 (2016)

Agronomic characteristics
characteristics ofAgronomicof new
new edibleedible chrysanthemum
chrysanthemumcultivar
cultivar‘Yamaen‘YamaenK4’
K4’
inducedinduced by heavy-ion beam irradiation
irradiation
S. Endo,*1 Y. Saito, *1 A. Abe,*1 and T. Abe*2
Boiled petals of chrysanthemum are a traditional food in
Tohoku district and Niigata prefecture. The edible flower
cultivars (Shokuyou-giku) were converted from ornamental
cultivars with sweetness and a little bitterness. In recenttimes, edible chrysanthemum has been widely used as acolor decoration in Japanese food. The edible petals ofchrysanthemum are classified into purple petals and yellow
petals. The former type is shipped in autumn as a seasonal
product, while the latter is shipped nearly throughout theyear. The amount of production of edible chrysanthemum inYamagata prefecture is the largest in Japan. In Yamagata,edible chrysanthemum is successively shipped in
combination with some other cultivars. However, the mainyellow flower cultivar ‘Kotobuki’ shows a trend of
reduction in shipment quantity and deterioration in quality
due to the smaller flower size from late September. Thus, anincrease in shipment quantity is required in the off-season
month of October. Therefore, we developed new yellow
edible chrysanthemum, ‘Yamaen K4’, harvested from themiddle of October to the middle of November by mutation
breeding using heavy-ion beam irradiation.
In 2006, petals of yellow flower cultivar ‘Etenraku’ (bredusing somaclonal variation of ‘Kotobuki’ in Yamagata
prefecture 1)) were picked and sterilized. Subsequently,
petals were cut into approximately 1-cm squares andcultured on MS medium containing 5 mg/l BA and 5 mg/l
NAA. Then, they were irradiated with a 12C6+ ion beam(135 MeV/nucleon, LET 22.6 keV/µm) at 10 Gy at theRIKEN RI-beam factory. Irradiated samples had been
incubated at 25oC in 68.9 μmol m-2 s-1 (PPFD) with 16 h day
length for some time, and redifferentiated shoots weretransplanted on an MS medium for plant elongation androoting. Rooted plants were transferred to pots andacclimated to the outside air environment. In 2007, cutting
seedlings made from 859 individual lines were planted intoa greenhouse in November. These plants were evaluatedduring 2008-2011, and they had showed some mutation of
the flowering period (Table 1), flower configuration, andother agronomic characteristics. Finally, one mutant line
was selected in 2011. After it passed the field test, it wasapplied for seed and seedling registration in February 2015
and published for application in July as ‘Yamaen K4’.
The flowering period of ‘Yamaen K4’ was from October
to November and was different from that of the original
cultivar, ‘Etenraku’, the flowering period of which is fromJ u l y t o S ep t e m b er. T he h a r v e s t i n g p er io d wa s
approximately 2-3 weeks from the middle ofOctober to the

middle of November regardless of planting date and year
(Table 2). Flower head diameters were approximately 80-90
mm in the early profit stage, and these values are slightly
less than those of ‘Etenraku’. However, the average flower
head weight during the harvesting period is the same as thatof ‘Etenraku’, and it depends on the small reduction in theflower head diameter of ‘Yamaen K4’. The main color of
the inner side of the ray floret is 7B or 7C (reference
number of RHS Color Chart), that of the outer side is 7D or
8A, and all values are higher than the corresponding valuesfor ‘Etenraku’ (Fig. 1, Table 3). The ray floret type isspatulate and incurved, and the ratio of the former type isgreater than that for ‘Etenraku’. The total number of ray
florets in the flower head is the same as for ‘Etenraku’. In2010, the yield per stock was 2,429 g at the 7 May planting
and 1,765 g at the 6 June planting, which indicate that theearly planting yield tendency is as high as the late planting
yield. However, planting before the beginning of June
makes it difficult to harvest and control because the plantheight increases beyond 110 cm. In 2011, it was easier tohandle because the plant height was 86 cm in the case ofplanting at 27 June, and the yield per stock at that time was1,569 g (Table 2). The tasting evaluation of ‘Yamaen K4’
was good and almost the same as for ‘Etenraku’ .
Table 1. Mutation of flowering date using heavy-ion beam irradiation
Amount of individuals (%)
zz

Early5 (0.6)

Equivalent
218 (25.4)

zLate477 (55.5)

yNot yet flowering
159 (18.5)

Total859

z ; Early ; flowering 2 weeks before from original, Late ; flowering 2 weeks after from original, Equivalent ; other,y ; Containing decreased growth and dead individuals

ABFig. 1. Flower head of ‘Yamaen K4’ (A) and5 cm

original cultivar‘Etenraku’ (B)Table 2. Characteristics of ‘Yamaen K4’ and standard cultivar (2011)
Harvest datePlantMarketable yield per
PlantingheightCultivar
Number ofWeightdateEarliest Latest(g)(cm)z flower head
Yamaen K4 14 Oct. 14 Nov. 110
598
1,794
6 Jun. Etenraku
12 Aug. 14 Nov. 56
413
1,188
Kotobuki
29 Aug. 21 Nov. 88
640
1,593
Yamaen K4 14 Oct. 14 Nov. 95
376
1,442
16 Jun. Etenraku
12 Aug. 21 Nov. 50
367
1,132
Kotobuki
12 Sep. 7 Nov. 89
573
1,589
Yamaen K4 17 Oct. 14 Nov. 86
396
1,569
27 Jun. Etenraku
1 Sep. 14 Nov. 47
188597
Kotobuki
26 Sep. 25 Oct. 77
361
1,116z : M ean (n=5) , y : M ean in early stage of harvest period (n=30)

Weight perMarketableflower head (g)
3.0
2.9
2.5
3.8
3.1
2.8
4.0
3.2
3.1

Table 3. Flower head morphology of ‘Yamaen K4’ and original cultivar (2013)z
Flower head
Number of Main color of ray floretx
Ray floret
Cultivarz
Number Typey disc floretz
Inner
Outerdiameter (mm)Yamaen K487
215
3,230
7C
7D
Etenraku
91
220
2,3
177D
5D

*1

Horticultural Experiment Station of Yamagata Integrated AgriculturalResearch Center*2
RIKEN Nishina Center- 263 -z : M ean in the early stage of harvest period (n=20), y : 1;ligulate, 2;incurved, 3;spatulate, 4;guilled, 5;funnel shaped,
x : Reference number of RHS Color Chart (Japan garden plants standard color chart)

Reference

1) Hirono et al., Breed. Res. 1 (suppl. 2). 323, (1999). (inJapanese)