RIKEN Accel. Prog. Rep. 50 (2017)

Ⅲ-4. Radiation Chemistry & Biology

Effects of LET-dose (Gy) combination on germination and viability rates indurum wheat irradiated by heavy-ion beam
K. Murai,䠆1 Y. Kazama,䠆2 and T. Abe䠆2Durum wheat (Triticum turgidum ssp. durum) is atetraploid species with the genome constitution AABB thatwas derived from two wild diploid ancestral species: the A
genome from T. urartu and the B genome from Aegilops
speltoides or another species classified in the Sitopsis
section. Therefore, the tetraploid durum wheat genome
contains duplicated homoeologous genes, and thischaracteristic may increase the difficulty of screening formutants in durum wheat. 7R DYRLG WKLV SUREOHP ZH KDYH
FKRVHQ WR XVH FXOWLYDWHG GLSORLG HLQNRUQ ZKHDW T.
monococcum ZLWKWKH$PJHQRPHVLPLODUWRWKH$JHQRPHLQEUHDGZKHDWIRUGHYHORSLQJDODUJHVFDOHPXWDQWSDQHO1)
DQGVFUHHQHGDQGDQDO\]HGVHYHUDOPXWDQWVIURPWKHPXWDQWSDQHO However, durum wheat is an important crop species
for making pasta, and we have started to make a mutant
panel of durum wheat by heavy-ion beam irradiation. First,
we examined the effects of WKH/(7'RVH *\ FRPELQDWLRQRILRQEHDPLUUDGLDWLRQXVLQJ&DUERQ & DQG$UJRQ $U DVQXFOHL RQ WKH JHUPLQDWLRQ DQG YLDELOLW\ UDWHV LQ 0JHQHUDWLRQ Fig. 1. Effects of heavy-ion beam irradiation on thegermination and viability rates in M1 generation of durum
wheat. Percentages (%) of M1 individuals are shown in each
LET-Gy combination of heavy-ion beam irradiation using
Carbon (C) and Argon (Ar) as nuclei. Brue and red bars
indicate germination and viability rates, respectively.

Dry seeds of the durum wheat cultivar ³Langdon´ wereirradiated with 15, 30, or 50 Gy and 30, 50, or 70 keV ȝP-1
LET for 12C6+ ions or 2.5, 5.0, 7.5 10, or 20 Gy of 40Ar17+ions NH9ȝP-1) to determine the optimal conditions formutant generation, using the E5 beam line of Ring
Cyclotron (RRC) in the RIKEN RI-beam factory. Thegermination rate was examined using the irradiated seeds(called M1 seeds) that were sown in wet-paper-containing
petri-dishes. 150 seeds (50 seeds with three replications)were tested for each treatment. The germination rate was
not affected by heavy-ion beam irradiation conditions (Fig.
1). Surprisingly, seeds treated with a high dose of the Ar ion
beam also showed a normal germination rate.
The M1 seedlings were planted in the field in October
2014, and the survival ratio (viability rate) was observed in
May 2015 at the heading stage with three replications (Fig.
1). The viability rate was reduced to less than 80 % whenthe LET of the C ion beam was 70 keV ȝP-1. For the Ar ion
beam, the viability rate was reduced to less than 60% withdose greater than 7.5 Gy, and all plants were killed when
the dose was 10 and 20 Gy. Based on a previous result of
the relationship between viability rate and mutation rate in
diploid wheat (K. Murai, unpublished data), the LET-Gy
condition with 80% viability is optimal for mutantgeneration. As a follow up study, therefore, we are now
examining the condition with LET50-70Gy for the C ion
beam in addition to LET70-15Gy.
Durum wheat cultivars are usually late-heading and notsuitable for cultivation in Japan, because of a rainy seasonfrom June to July. All known cultivars of durum wheatshow pre-harvest sprouting when exposed to prolonged
rainfall before harvest. Furthermore durum wheat cultivars
are susceptible to Fusarium head blight disease. Because ofthese disadvantages, durum wheat has not been cultivated inJapan. Recently, one durum wheat cultivar ³Setodure´ wasdeveloped by the National Agriculture and Food
Organization. However, ³Setodure´ is still susceptible toFusarium head blight, and was therefore released in alimited manner in the Seto-uchi region which receives littlerain.
To develop durum wheat cultivars suitable for wide
regions in Japan, we are focusing on identifying mutationsof early heading, short culm, and resistance against
pre-harvest sprouting and Fusarium head blight in durum
wheat using heavy-ion beam mutagenesis.

䠆1

Department of Bioscience, Fukui Prefectural University
RIKEN Nishina Center
This work was supported by Council for Science, Technology andInnovation (CSTI), Cross-ministerial Strategic Innovation Promotion
3URJUDP 6,3  ³7HFKQRORJLHV IRU FUHDWLQJ next-generation agriculture,
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䠆2- 270 -References
1) K. Murai et al., Nucl. Instrum. Meth. Phys. Res. B 314, 59(2013).
2) A. Nishiura et al., Breeding Sci. 64, 213 (2014).