Ⅲ-4. Radiation Chemistry & Biology

RIKEN Accel. Prog. Rep. 53

Development of mutagenesis technique for leguminous crops using
heavy-ion-beam irradiation and screening of useful mutants
P. Siviengkhek,∗1 K. Ishii,∗2 T. Sato,∗2,∗3 Y. Hayashi,∗2 and T. Abe∗2Leguminous crops (soybean, mungbean, and peanut)
are important sources of lipid and protein for the humandiet. In Lao PDR, mungbean and soybean productions
are well suited to local soil and temperature conditions,which include both wet and dry seasons. However, soybean and mungbean productions are currently operated
on a small scale and at a household level depending on
the local farmers’ skill. There are several factors hampering the expansion of the production area and yieldfor both crops. Mungbean has an indeterminate ﬂowering habit, which implies that it does not have a deﬁned
ﬂowering period and will continue ﬂowering as long as
adequate soil moisture is provided. Consequently, harvesting mungbean is costly because of its long cultivation period and loss of grains from early-matured pods.
On the other hand, most varieties of soybean are sensitive to the photoperiod. It is necessary to cultivate
suitable varieties depending on the locations or seasons;otherwise, some varieties ﬂower early, resulting in a low
production yield. To overcome these diﬃculties, productions of mungbean with a determinate ﬂowering trait
and soybean with a non/less photosensitive trait are desired. Some mutants of soybean have been obtained withcarbon-ion-beam irradiation.1–3) In this study, to determine an eﬃcient condition for mutant induction, we irradiated mungbean and soybean with heavy-ion beams atvarious absorbed doses and observed the eﬀects on plantgrowth.
Dry seeds of mungbean (Vigna radiate ‘Pakse’) andTable 1. Germination and growth of soybean (ARC3) irradiated by C-ion and Ar-ion beams at diﬀerent doses.
Ion
ControlC

Dose(Gy)

Germination
rate
(%)

Survivalrate(%) *0
90.0
90.0
25
63.3
63.3
50
70.0
70.0
75
70.0
56.7
100
80.0
63.3
125
80.0
23.3
150
80.0
43.3
200
80.0
16.7
Ar5
83.3
83.3
1090.0
83.3
20
90.0
76.7
30
63.3
26.7
* Number of growing plants / 30 sown seeds** Plant height /average height of control plants∗1∗2∗3GrowthIndex **
1.00
0.99
0.91
0.82
0.73
0,50
0.68
0.26
0.88
0.80
0.65
0.39

Maize and Cash Crop Research Center, National Agriculture,
Forestry and Rural Development Research Institute (NAFRI)
RIKEN Nishina Center
Graduate School of Agriculture, Tohoku University

Table 2. Germination and growth of mungbean (Pakse) irradiated by C-ion and Ar-ion beams at diﬀerent doses.
IonControlCArDose(Gy)0255075100125150
51020304050Germinationrate(%)
100.0
96.7
93.3
80.0
96.7
96.7
96.7
86.7
90.0
86.7
90.0
83.3
63.3

Survivalrate
(%) *
83.3
80.0
83.3
80.0
86.7
93.3
70.0
83.3
70.0
73.3
90.0
83.3
63.3

GrowthIndex **
1.00
0.93
0.98
0.95
0.97
0.83
0.86
1.00
0.92
0.91
0.92
0.66
0.54

soybean (Glycine max L. Merr ‘ARC3’) are packed intoa rectangular plastic box or into a plastic petri dishin which a cork sheet is bedded to lay seeds in a single layer. Seeds of mungbean and soybean packed intothe rectangular plastic box were irradiated with C ions(135 MeV/n) at doses of 0–150 Gy and 0–200 Gy, respectively. The LET of C-ion beams was controlled to30 keV/µm. Seeds packed into the plastic petri dish wereirradiated with Ar ions (160 MeV/n) at doses of 0–50 Gy.
The LET of C-ion beams was controlled to 188 keV/µm.
After irradiation, the seeds were sowed at an experimental ﬁeld.
Soybean showed sensitivity to both C-ion (in the rangeof 0–200 Gy) and Ar-ion (0–50 Gy) beams (Table 1). Although mungbean showed lower sensitivity, the growthrate was reduced to 0.83 after 125 Gy irradiation of a Cion beam and to 0.54 after 50 Gy irradiation of an Ar-ion
beam (Table 2). To optimize the mutation rate, we determined the minimal doses that yield a growth index appropriate for mutagenesis with heavy-ion beams. Therefore, we determined the appropriate absorbed doses formutant selection as follows: for soybean, C-ion beams at
75 and 100 Gy, and Ar-ion beams at 10 and 20 Gy wereused; for mungbean, C-ion beams at 125 and 150 Gy, andAr-ion beams at 30 and 40 Gy were used. Among theirradiated soybean plants, some male sterile plants werefound. The highest percentage of male sterile plants was
67% after Ar-ion-beam irradiation at 20 Gy, followed by
33%, 17%, and 17% after C-ion-beam irradiation at 150,
125 and 100 Gy, respectively. On the other hand, there
were no male sterile plants among mungbean plants.
References

1) H. Kuribara et al., RIKEN Accel. Prog. Rep. 43, 286 (2010).
2) S. Arase et al., Plant Biotech. 28, 323 (2011).
3) R. Grasso et al., PLoS One 11, e0167998 (2016).

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