Ⅲ-4. Radiation Chemistry & Biology

RIKEN Accel. Prog. Rep. 50 (2017)

New cherry blossom cultivars induced by C-ion beam irradiation
S. Ishii, 䠆1 Y. Hayashi, 䠆2 T. Hirano, 䠆2, 3 Y. Kazama, 䠆2 and T. Abe䠆2A new color cherry blossom with pale-yellow flowers,‘Nishina Zao’ was created by irradiating the greenish‘Gyoiko’ scions with C ions.1) It became the first plant to beregistered under the Seeds and Seedlings Law by RIKEN adecade ago. Another cultivar of the cherry blossom tree,‘Nishina Otome’ does not require a certain period of cold
winter weather to induce flowering in the spring. 2) The
winter temperatures have not been sufficiently low due tothe global warming in recent years. This climate change has
resulted in a decrease in the number of cherry blossoms inspring. These two cultivars are propagated clone plants ofthe mutant branch. We have succeeded in creating three
new cherry blossom cultivars by irradiating cherry scionswith C ions. With the original cultivars, ‘Shungetsuka’ and‘Beniyutaka’, it is difficult to obtain seeds with germination
capacity. The irradiation treatment on scions increased thegermination rates of seeds from 0.5 to 12% and 0 to 56%, in‘Sungetsuka’ and ‘Beniyutaka’, respectively. Three newcultivars were selected from the progeny plants of theirradiated plants.
‘Nishina Haruka’ and ‘Nishina Komachi’͂Shungetsuka’ is a Japanese ornamental cherry cultivar
having double flowers (I3̽3.5 cm) with 21 to 50 petals. Its
scions were irradiated with carbon-ions (135 MeV/u, LET
22.6 keV/Pm) at the doses of 5, 7.5, and 10 Gy. The
irradiated scions were grafted on rootstocks. Twenty of theirradiated plants showed no change in their flower color andshape in 2008. Subsequently, we attempted natural crossing
between irradiated plants from 2008 to 2009. Plants
irradiated at a dose of 5 Gy showed good growth and bore
300 ̽ 500 cherries per plant. The original
cultivar ’Shungetsuka’ bears cherry fruits with low
germination capacity. Specifically, only 23 plants weregrown from approximately 5000 cherry seeds of the original

cultivar. On the other hand, 296 plants were grown fromapproximately 2500 cherry seeds from the fruits borne by
the irradiated plants. The progeny plants bloomed in 2012,
and the characteristics of the mutant lines were confirmed
to be stable. We produced two new cultivars, named‘Nishina Haruka’ and ‘Nishina Komachi’, from the mutantlines irradiated at 5 Gy. ‘Nishina Haruka’ had doubleflowers (I4.1̽4.2 cm) with 23 to 25 petals: they were 1.3
times larger than the flowers of the original cultivar. This
cultivar also bore sweet cherries (I1cm). ‘Nishina
Komachi’ had small single flowers (I1.3̽1.4 cm) withfive petals, which do not open fully. These two cultivars
were submitted for cultivar registration in September 2012.
‘Nishina Tomoka’’Beniyutaka’ (Prunus lannesiana) has double flowers(ϕ 5 cm)(I5cm)withwith1515̽20
̽ 20 petals. Its scions were irradiated withcarbon-ions (135 MeV/u, LET 22.6 keV/Pm) at a dose of 10
Gy in 2005. The irradiated scions were grafted on therootstock. No change was observed in the flower color andshape of the three irradiated plants in 2007. Even though theoriginal cultivar ’Beniyutaka’ does not bear cherries, one of
the irradiated plants bore 9 cherries. We sowed the seeds
from these cherries. Of these nine seeds, five germinated.
Three of these germinated seeds grew into progeny plantsthat bloomed in 2011. One mutant line, named ‘Nishina
Tomoka’, had single flowers (I3.2̽3.6 cm) with 5 petals.
The rim of its flowers was deep pink. ’Beniyutaka’ wasbred in the Hokkaido area because the cold region wassuitable for its cultivation. However, ‘Nishina Tomoka’showed good growth even in the relatively warmer
Shizuoka Prefecture. This cultivar was easy to propagate bycuttings, and was submitted for cultivar registration in
September 2016.

(b)

(a)

(c)Fig. 1. Flowers of new cultivars.
(a) Nishina Haruka, (b) Nishina Komachi, (c) Nishina Tomoka
References
䠆1

JFC Ishii Garden
䠆2
RIKEN Nishina Center
䠆3
Faculty of Agriculture, University of Miyazaki

1)2)- 275 -S. Ishii et al.; RIKEN Accel. Prog. Rep. 42, xi (2009).
S. Ishii et al.; RIKEN Accel. Prog. Rep. 44, xiii (2011).