Ⅲ-4. Radiation Chemistry & Biology

RIKEN Accel. Prog. Rep. 53

Improvement of the Brix content of the sweet potato “Anno-Beni”
by mutation induced using heavy-ion-beam irradiation
T. Hashiguchi,∗1 K. Yamane,∗1 J. Nagai,∗1 F. Tojima,∗1 K. Ishii,∗2 Y. Hayashi,∗2 and T. Abe∗2
Table 1. Line selection by dry-matter ratio of mutants ofthe sweet potato “Anno-Beni” obtained by C-ion-beamirradiation.

Dose(Gy)

Number ofregenerated
shootsNumber of
selectedplants

5107

25

1070

51519

1

Table 2. Dry matter and Brix content of 4 mutant lines ofsweet potato.

Line nameDose(Gy)Testedroottubers

Mean ofdrymatterratio (%)

Mean ofbrix(%)

No.15
No.17
No.27
No.34
Control(B1)

555
10-77
55
16

34.3
34.1
35.9
36.0
33.3

12.4
12.7
13.0
13.2
11.6

15

Steamed sweet potato Brix (%)

Heavy-ion-beam irradiation eﬀectively induces plantmutations and is used for plant breeding.1) The sweet
potato cultivar “Anno-Beni,” which has a high sugar
content, is an important and special product in theTanegashima island area. However, the weather cancause the sugar content to be unstable and the productto taste bad. Sugar is produced from starch by storage and heat, and it turns into sweetness. However, thedry-matter content and starch content change according to the harvest time, storage period, and tuber root
position. Therefore, by inducing mutations throughheavy-ion-beam irradiation, varieties and strains witha stable sugar content have been selected. In thisstudy, we measured the dry-matter contents of selectedmutants irradiated with a heavy-ion-beam, and in thisreport, we describe the eﬀect of the irradiation on thesugar content.
Embryogenic callus derived from the stem apex of
the “Anno-Beni” B1 line were irradiated with a C-ionbeam (LET 23 keV/µm) at a dose of 5, 10, and 15 Gy
in 2015. Regenerated plants that grew normally wereobtained from the irradiated callus. Subsequently, wepropagated 196 individual plantlets to 5 clone plants,respectively, and cultivated them in the ﬁeld of KIAD
∗ 1, Kumage Branch for line selection in 2016. We
selected 31 lines that grew better and had higher drymatter contents than the control (Table 1).
In the next year, the 31 selected lines were grownby vegetative propagation, and 5 individual plants perline were cultivated in the ﬁeld. We investigated theplant growth and dry-matter contents in 2017. The
root tubers of the 4 lines were steamed and, diluted
with water in a 1 : 1 ratio, their Brix contents weremeasured. Brix is the sugar content of an aqueous solution. It is known that there is a correlation between
the dry-matter rate and Brix percentage of tuberous
roots in sweet potato.2) Although the means of the drymatter content in 4 mutant lines showed no signiﬁcantdiﬀerence, the Brix contents of 4 lines were higher thanthose of the control (Table 2).
Some root tubers produced by mutant lines had
a higher Brix percentage and dry-matter rate thanthe control (Fig. 1). These results, obtained throughthe individual selection of mutant lines showing better
growth and higher dry-matter contents than the control, suggest that high-Brix-content strains could beselected.

141312Control

11C5Gy No.15 n=7C5Gy No.17 n=7109n=16C5Gy No.27 n=5C10Gy No.34 n=5253035
Dry matter content (%)

40Fig. 1. Correlation between Brix content and dry-matterratio in root tubers produced by 4 mutant lines.

References∗1∗2

Kagoshima Prefectural Institute for Agricultural Development (KIAD)
RIKEN Nishina Center- 207 -

1) T. Abe et al., Breed. Res. 16, 67 (2014).
2) M. Ouchida, K. Ueno, Rep. Kyushu Br. Crop Sci. Soc.
Japan 80, 22 (2014).