RIKEN Accel. Prog. Rep. 50 (2017)

Ⅲ-4. Radiation Chemistry & Biology

Production of flower color mutants of spray-mum Southern Chelsea
by Ar-ion beam irradiation
M. Tamari,1 Y. Tanokashira,1 Y. Hayashi ,2 T. Hirano,2,3 and T. Abe2
Heavy-ion beam irradiation effectively induces mutationsof plants and has been used in plant breeding.1) Ar-ion
beam irradiation is expected to expand the spectrum ofmutant phenotypes and mutation rate owing to its higher
LET compared to a C-ion beam. We previously reported theinduction of flower-color mutants of spray-mum cultivar‘Southern Chelsea’ cuttings using Ar-ion beam irradiation.2)
In addition, we reported the effects of Ar-ion beamirradiation on the regeneration from leaf blades3) andspeculated that Ar-ion beam irradiation on leaf blades was
not practical because of the low relative regeneration
fequency of less than 10% at doses of 2 Gy Ar-ion beamirradiation.4) Here, we report the production of flower-color
mutants by the irradiation of stem segments of ‘SouthernChelsea.’
Eighty and forty stem segments of ‘Southern Chelsea,’
were irradiated with Ar-ion beams (LET: 280 keV/μm) at
doses of 0.5, 1, 2, and 3 Gy and C-ion beams (LET: 23keV/μm) at doses of 1, 2, and 3 Gy, respectively. After
irradiation, these tissues were cultured in vitro, and 3 nodes
that had axillary buds cut out from an extended shoot weresubcultured to separate mutation sites. This subculture step
was repeated when shoots sprouted from axillary buds wereextended sufficiently. Plantlets grown from re-subcultred
nodes were transferred to a greenhouse to investigate
flower- color mutation.
Table 1. Flower-color mutation induced by heavy-ion beamirradiation.
Variation
sourceLine
class

NumberofDose(Gy)plants
(%)

0.5
12Ar
3
Total
0
12C3
Total
0171
165
151
74561
12111
102
10131446

Number of flower-color mutants

1)

White

Yellow Orange

2131124
60011

Yellowish
pink

Lightpink

Other

1
1881
100201

NumberMutationofrate(%)
mutants

01146210001111) Regenerated and flowered plants after irradiation.

100.69.3
8.1
3.7
000
1.0
0.3
2.2

The numbers of flower-color mutants obatined by Ar-ion
beam irradiation at 1, 2, and 3 Gy were 1, 14, and 6,
respectively (Table 1). On the other hand, only one
flower-color mutant was obtained by C-ion beam irradiation
at all doses (Table 1).
The flower colors of mutants obtained by Ar-ion beamirradiation were white, yellow, orange, yellowish pink, andlight pink (Table 1). This fact suggests that the direction of
flower-color mutation by Ar-ion beam irradiation is thedecrease or disappearance of anthocyanin and increase ofcarotenoid. Especially, one yellow-flower mutant, which
was thought to be difficult to obtain from ‘Southern
Chelsea,’ having pink flowers, appeared after Ar-ion beamirradiation at 2 Gy (Table 1). It is thought that thisyellow-flower mutant was caused by the disappearance ofanthocyanin and simultaneous increase of carotenoid. Somemutants also showed the morphological variation of flower
shape because of Ar-ion beam irradiation (data not shown).
The growth of many mutants from stem segments withAr-ion beam irradiation was equal to that of control plants(data not shown). Because the growth of almost all mutantsfrom leaf blades by the same irradiation condition waslower than that of control plants,4) this result suggests thatstem segments will be more suitable for producing mutantsof spray-mum using Ar-ion beam irradiation.
From the results presented above, it has become possible
to produce many flower-color mutants of spray-mum by
Ar-ion beam irradiation to stem segments. On the basis ofthese results, it is supposed that the low rate of regenerationand mutation by Ar-ion beam irradiation in several
spray-mum cultivars will be improved by using stem
segments as irradiation targets.
The present study was supported by the Council forScience,
TechnologyandInnovation(CSTI),
Cross-ministerial Strategic Innovation Promotion Program(SIP),  Technologies for creating next-generation
agriculture, forestry and fisheries  (funding agency:Bio-oriented Technology Research Advancement Institution,NARO).
References
1) T. Abe et al.: Breed. Res. 16, 67 (2014).
2) Y. Tanokashira et al.: RIKEN Accel. Prog. Rep. 47, 297 (2014).
3) Y. Tanokashira et al.: RIKEN Accel. Prog. Rep. 48, 306 (2015).
4) Y. Tanokashira et al.: RIKEN Accel. Prog. Rep. 49, 261(2016)

Kagoshima Prefectural Institute for Agricultural Development
RIKEN Nishina Center
3
Faculty of Agriculture, University of Miyazaki
2- 274 -