Ⅲ-4. Radiation Chemistry & Biology

RIKEN Accel. Prog. Rep. 47 (2014)

Effect of heavy-ion beam irradiation on seeds reductionof ‘Konta’ kumquat fruit
K. Tomura,*1 T. Teraoka,*2 T.Nakajima, *1 Y. Kobayashi,*1 I. Sawano,*3Y. Hayashi,*4 N. Fukunishi,*4 T. Abe*4*1

Fruit Tree Res. Center, Shizuoka Res. Inst. of Agric. and For.

*2present：Shizuoka Agric. Promotion div.

*3

present：Shizuoka Toubu Agric. and For. Office*4RIKEN Nishina Centerrate (Fig. 2). Furthermore, we isolated the branches bearingmore seeds reduced fruits from these selected vM1 plants.
The fixation of seeds reduction is currently underinvestigation.

Fig.1 fruit surfaces after equatorial cuts.
Perfect seeds (left) and reduced seed (right)
Table 1. Appearance of seeds reduced fruits of ‘Konta’ by Ne-ion beam irradiation
Irradiation
NeControl

Number of vM13629

Number of
total fruits
2125
1651

Number of perfect seeds (%)
0-2 seeds>3 seeds
128(6%)
1997(94%)21(1%)
1630(99%)

Table 2. Appearance of seeds reduced fruits of ‘Konta’ by C-ion beam irradiation

128
5㻥㻜㻤㻜㻣㻜㻢㻜㻡㻜㻠㻜㻟㻜㻞㻜㻝㻜㻜㻺㼑㻙㼕㼛㼚

Number oftotal fruits
7307
208㻥㻜
㻤㻜㻣㻜㻢㻜㻡㻜㻠㻜㻟㻜㻞㻜㻝㻜㻜

Number of perfect seeds (%)
0-2 seeds>3 seeds
962(13%)6345(87%)
17(8%)
191(92%)㻯㻙㼕㼛㼚㼚㼠㼞㼛㻺㼛 㼘㻚㻢
㻺㼛㻚㻣㻺㼛㻚㻤㻺㼛㻚㻥㻺㼛㻚㻝㻺㼛 㻜㻚 㻝㻝㻺㼛㻚㻝㻺㼛 㻞㻚 㻝㻟㻺㼛㻚㻝㻺㼛 㻠㻚 㻝㻡C
Control

Number of vM1

㻯㼛

Irradiation㻾㼍㼠㼕㼛㻌㼛㼒㻌㼟㼑㼑㼐㼟㻌㼞㼑㼐㼡㼏㼑㼐㻌㼒㼞㼡㼕㼠㻌㼜㼑㼞㻌㼜㼘㼍㼚㼠㻯㼛㼚㼠㼞㼛㻺㼛 㼘㻚㻝
㻺㼛㻚㻞
㻺㼛
㻚㻟
㻺㼛
㻚㻠
㻺㼛
㻚㻡

‘Konta’ kumquat was found as a bud mutant in the field bya farmer in Shizuoka Prefecture. ‘Konta’ has some uniquecharacteristics compared with ‘Neiha’ kumquat. It has
higher sugar content and lesser citric acid content than
‘Neiha’ kumquat, which tastes extremely good. On the otherhand ‘Konta’ has more seeds (6-7) than ‘Neiha’ (5-6). 1) If
we can develop seedless ‘Konta’, it will be a valuablecultivar. Recently, heavy-ion beam irradiation has beenreported as an effective mutation breeding technique.
Especially since ‘Konta’ has multi-embryonic seeds, it isdifficult to breed this cultivar.
In this study, we investigated the effect of heavy-ion beamirradiation on seed reduction and attempted to obtain amutant of ‘Konta’ kumquat fruit with reduced number ofseeds.
In 2007 and 2008, dormant scions from the hard branchesof ‘Konta’ kumquat were irradiated with 12C6+ and 20Ne10+
at a dose of 10Gy(135 MeV/u, 61.1 keV/μm). After
irradiation, the scions were grafted on Poncirus trifoliata tocreate the vegetative mutant 1(vM1) generation. After
sprouting, the treetops were subjected to cutting back atleast 3 times. As the control, original ‘Konta’ was grafted onP. trifoliata. These plants are pollinated naturally, andsuperfluous fruits were not removed for securing thenumber of fruits.
We counted the number of perfect seeds on the equatorial
cut surface of all the fruits obtained from Ne-ion irradiatedvM1 and C-ion irradiated vM1 in 2011 and 2012. We
considered fruits with 0-2 perfect seeds as “seeds reducedfruit” (Fig. 1) and calculated the ratio of seeds reduced
fruits (i.e., number of fruits with two or less seeds/numberof examined fruits).
For Ne-ion beam irradiation, the appearance ratio of seeds
reduced fruit in vM1 plants was 6%, while that in thecontrol was 1% (Table 1). One of thirty-six vM1 plants bore
more than 80% seeds reduced fruits by Ne-ion beamirradiation. For C-ion beam irradiation, the appearance ratioof seeds reduced fruit in vM1 plants was 13%, while that in
the control was 8% (Table 2). In four plants, the ratio ofseeds reduced fruit per vM1 plant exceeded 70% by C-ion
beam irradiation. The ratios of seeds reduced fruit percontrol plant were less than 10% in both the irradiation
studies. These results indicate that heavy-ion beamirradiation is effective for seed reductions in ‘Konta’ fruit.
We selected the vM1 plants with high seeds reduced fruits

Fig. 2 Examples of vM1 plant with high seeds reduced fruits rate.
Vertical bars represent ± SD(Ne: n = 29, C: n = 5).

References
1) Y. Araki : Izu Agric. Res. Center, Shizuoka Res. Inst. of Agric.
and For. Rep. (2003) p.158-159- 298 -