JAEA-Review-2010-065.pdf:15.99MB - 日本原子力研究開発機構

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Effects of Ion-beam Irradiation on Germination and
Growth of Seedlings of Red Pepper ‘Hirosaki zairai’
M. Tomikawa a) , T. Maeda a) , K. Honda a) , K. Saga a) , R. Ishikawa a) , Y. Akita b) ,
R. Yoshihara b) , S. Nozawa b) and I. Narumi b)
a) Faculty of Agriculture and Life Science, Hirosaki University,
b) Radiation-Applied Biology Division, QuBS, JAEA
Red pepper (Capsicum annuum L.) ‘Hirosaki zairai’ is a
local variety grown around Hirosaki city in Aomori
prefecture, and it has been promoted as one of the ‘valuable
local brands’. In this study, we tried to create additional
values on this unique variety via mutation breeding using
ion beam irradiation which has been widely adopted on
many crops 1–3) .
Seeds of ‘Hirosaki zairai’ placed on petri dishes were
irradiated with 220-MeV carbon-ion beams accelerated by a
TIARA AVF cyclotron (JAEA, Takasaki, Japan), at the
doses of 0, 10, 20, 30, 40, 50, 60, 70, 80, 100, 200 and
300 Gy. One hundred seeds were irradiated at each dose.
All the treated seeds were sown on 90 mm petri dishes
with moistened filter papers (25 seeds on each dish × 4
replication), and incubated at 25 °C. Germinated seeds
were counted daily, and then were transplanted to 128-hole
cell tray and cultivated in a greenhouse at Hirosaki
University. Effects of the ion beam irradiation on M 1
plants were evaluated by examining the shapes of
cotyledons, plants and fruits. Plant height and number of
joints were measured once a week from 40 days after
sowing. Ten M 1 seedlings from each dose were
transplanted to #7 plastic pots in a greenhouse, and the rest
of the seedlings were transplanted on the research field of
Hirosaki University after 90 days from sowing. Immature
green fruits (10 fruits per each dose) were collected from M 1
plants growing both in greenhouse and open field at
20 days after flowering. Red fruits were also collected
after fully matured. Length, width in the middle part,
width in the shoulder part and weight of each fruit were
measured. All the irradiated plants were examined on the
indication of mutation by visual judgment. Some flowers
in a green house were covered with mesh net for
self-pollination. Same treatment was conducted on the
visually–mutated plants.
Delay of germination was observed in accordance with
dosage, however, germination rates were more than 96 %,
and no visual mutation was observed in the shape of radicles
in all the treatments. Curled cotyledons were observed
only in the ion-beam irradiated plants, and degree of the curl
got larger in accordance with dosage. Both emergence
rates of shoot and survival at 60 days after sowing got lower
at the doses over 50 Gy, and almost all seedlings died over
70 Gy (Fig. 1). Plant heights were rather lower in the
plants irradiated with high dosage at May 20 (72 days after
sowing): however, the differences in plant heights got
smaller at June 18 (101 days after sowing). No significant
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difference was observed in the number of joints. These
results suggested that the physical energy of ion beam
irradiation, especially over 50 Gy, was seemed to cause
significant effects on the growth of young seedlings. Some
irregular plants in the shape were observed over 10 Gy, such
as dwarfing, short internode, and one short internode plant
was found to have much more fruits in comparison with
non-irradiated control. We successfully earned M 2 seeds
from such ‘visibly-mutated’ plants. Further investigation
was needed whether such mutations were genetically fixed.
No significant difference was observed in the shape of fruits
within the plants from which the green or red fruits:
however, some extremely small fruits and ‘doubly–fruited’
i.e. prolificated fruits (a small fruit was formed in a fruit)
were observed in 40-Gy irradiated samples. This result
suggested that ion beam irradiation also affected on fruiting.
The results of this study showed that ion beam irradiation
seemed to be applicable on the mutation breeding of red
pepper ‘Hirosaki zairai’, and that mutation could be caused
at the absorbed dose of over 10 Gy.
References
1) I. Honda et al., Euphytica. 151 (2006) 61.
2) H. Yamaguchi et al., Breeding Sci. 59 (2009) 169.
3) E. Kondo et al., Plant Biotech. 26 (2009) 565.
Survival rate (%)
100
80
60
40
20
0
0
10
20
30
40
Fig. 1 Effect of ion beam irradiation on the survival
rate of the seedlings of red pepper ‘Hirosaki zairai’
at 60 days after sowing.
50
60
70
80
Dosage of ion beam(Gy)
100
200
300