Ⅰ. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 49 (2016)

BreedingofofSummer-Autumn
Summer-Autumn Flowering
Flowering Chrysanthemum
Breeding
Chrysanthemumcv.
cv.Hakuryo
Hakuryolittlegeneration
generation ofof malformed
malformed flower
with aa littlewithflower
A. Hisamura, *1 D. Mine, *2 T. Takeda, *1 T. Abe, *3 Y. Hayashi, *3 and T. Hirano *4
has these following characteristics. Harvest in natural
flowering is from the last ten days of May to the beginningof June, which is about 3 weeks earlier than
“Iwano-hakusen”. The flowering days after the end of thelong-day treatment is about 45 days. The stem grows fasterand is 4 cm – 5 cm longer than “Iwano-hakusen”. The sizeof the flower at harvest is about the same or little bigger
than “Iwano-hakusen”. The number of ray flowers is about
the same or little lesser than “Iwano-hakusen”. Theoccurrence rate of malformed flowers is substantially lessthan that of “Iwano-hakusen” in September-flowering type
plants, which is only about 10% (Fig. 2).
“Hakuryo” is becoming popular gradually because thecommercializing rate has been increasing as the generationof malformed flowers decreases, so that farmers can expect
financial stability. However, “Hakuryo” has two problems:
its weight is slightly lighter because of its longer stem andleaf scorch is often seen. Therefore, we need to select aheavier line and establish a cultivation technique to improve
the quality of “Hakuryo”.

Chrysanthemum is the main element of flowering plant
production in Nagasaki Prefecture. Its growing area spreads
over 168 hectares and has an output of approximately 3,500
million yen. A summer-autumn flowering Chrysanthemum
cv. Iwano-hakusen has come to a main summer-autumn
Chrysanthemum cultivar in Nagasaki Prefecture because it
is one of the labor-saving cultivars with no lateral shoot anddose not require a shading apparatus controlling the day
length for flowering. However, “Iwano-hakusen” has aproblem that malformed flowers can be seen significantly
among September-flowering type plants (fig. 1-A,B) due tohigh temperatures in September. This problem is serious
because those malformed flowers cannot be commercialized
and it directly affects the farmer’s business situation. Thus,
developing a new cultivar of summer-autumn
Chrysanthemum having minimum generation of malformed
flowers had been desired. Therefore, we tried to breed anew cultivar having minimum generation of malformed
flowers by using heavy-ion beam irradiation. As a result, wesucceeded in breeding a new cultivar known as “Hakuryo”
in 2014.
We irradiated C-ion beams (LET: 23keV/µm) of 10 Gy
to “Iwano-hakusen” at RIKEN Nishina center in February
2011, and selected a new cultivar “Hakuryo”. We irradiatedC-ion beams to 1,440 scions, and obtained 3,702 derivatives
from the irradiated scions as a mother stock. Among the3,702 derivatives, 1,620 showed malformations such as
forked or fasciated stems. From the rest of the derivatives,
2,082 were planted and cultured under normal lightculturing. After that we selected well-formed flowers on thefirst selection.The second selection of well-formed flowers
in the next generation was performed in 2012. Then on thethird selection, “Hakuryo” was isolated. Large-scale
experimental production of “Hakuryo” was performed at
the agricultural center field and at the local field. We
applied for registration of the variety on the March 12, 2015
because the stability of characters was confirmed.
“Hakuryo” is a variety of Summer-Autumn Flowering
Chrysanthemum and has large white petals (White-group
NN115-C on the R.H.S. color chart) (Fig. 1-C, D). It does
not need a shading apparatus for flowering, and shippingfrom July to September is possible using long-day treatment
under light culture. Since its neck is short, the balance ofupper leaves arrangement is preferred in the market (Fig.
1-C). As compared to “Iwano-hakusen”, “Hakuryo”

ABCDFig. 1 The normal flower of “Iwano-hakusen” (A) andmalformed flower (B). The upper side of “Hakuryo” (C)and in full bloom (D).

Incidence

10080604020

Iwanohakusen

Agriculture and Forestry Technical Development Center, Nagasaki
Prefectural Government＊2
Shimabara Development Bureau＊3
RIKEN Nishina Center＊4
Faculty of Agriculture, Miyazaki University＊1Hakuryo
2013

Iwanohakusen

Hakuryo2014

Fig.2 Incidence of Flower malformation in Septemberflowering type plants※１）Short diameter/long diameter= 9/10 to 1/1 is nomal， 4/5 to 9/10 ismalformaion （slight），and 7/10 to 4/5 malformaion（serious）- 24 -