Genotypic difference in 137Cs accumulation and transfer from the contaminated field in Fukushima to azuki bean (Vigna angularis)

Journal of Environmental Radioactivity 158-159 (2016) 138e147

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Genotypic difference in 137Cs accumulation and transfer from the contaminated field in Fukushima to azuki bean (Vigna angularis) Khin Thuzar Win a, Aung Zaw Oo a, Katsuhiro Kojima a, Djedidi Salem a, Hiroko Yamaya b, Sonoko Dorothea Bellingrath-Kimura c, Norihiko Tomooka d, Akito Kaga d, Naoko Ohkama-Ohtsu e, Tadashi Yokoyama e, * a

Faculty of Agriculture, Tokyo University of Agriculture and Technology, Saiwaicho 3-5-8, Fuchu, Tokyo, 183-8509, Japan College of Bioresources Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa, 252-0880, Japan Institute of Land Use Systems, Leibniz Center for Agriculutral Landscape Research, Eberswalder Straße 84, 15374, Müncheberg, Germany d Gene Bank, National Institute of Agrobiological Sciences, 2-1-2 Kannondai, Tsukuba, Ibaraki, 305-8602, Japan e Instutute of Agriculture, Tokyo University of Agriculture and Technology, Saiwaicho 3-5-8, Fuchu, Tokyo, 183-8509, Japan b c

a r t i c l e i n f o

a b s t r a c t

Article history: Received 21 January 2016 Received in revised form 9 April 2016 Accepted 10 April 2016 Available online 19 April 2016

The screening of mini-core collection of azuki bean accessions (Vigna angularis (Willd.) Ohwi & Ohashi) for comparative uptake of 137Cs in their edible portions was done in field trials on land contaminated by the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. Ninety seven azuki bean accessions including their wild relatives from a Japanese gene bank, were grown in a field in the Fukushima prefecture, which is located approximately 51 km north of FDNPP. The contamination level of the soil was 3665 ± 480 Bq kg
1 dry weight (137Cs, average ± SD). The soil type comprised clay loam, where the sand: silt: clay proportion was 42:21:37. There was a significant varietal difference in the biomass production, radiocaesium accumulation and transfer factor (TF) of radiocaesium from the soil to edible portion. Under identical agricultural practice, the extent of 137Cs accumulation by seeds differed between the accessions by as much as 10-fold. Intervarietal variation was expressed at the ratio of the maximum to minimum observed 137Cs transfer factor for seeds ranged from 0.092 to 0.009. The total biomass, time to flowering and maturity, and seed yield had negative relationship to 137Cs activity concentration in seeds. The results suggest that certain variety/ varieties of azuki bean which accumulated less 137Cs in edible portion with preferable agronomic traits are suitable to reduce the 137Cs accumulation in food chain on contaminated land. © 2016 Elsevier Ltd. All rights reserved.

Keywords: Azuki bean 137 Cs accumulation Screening Transfer factor

1. Introduction Soil has been concerned as a major sink for radioactive deposition following the accident of the FDNPP, in Japan on March 11th, 2011. Radiocaesium is one of the most important radioactive contaminants after the explosion of a nuclear power station, such as those which occurred in Chernobyl and Fukushima (Kobayashi, 2011; Gonz
alez, 2012). Given that the physical half-life of 134Cs is 2.06 years and that of 137Cs is 30.17 years, the impact of 137Cs contamination will continue for some decades. The deposition of

* Corresponding author. Tokyo University of Agriculture and Technology, Institute for Agriculture, Biological production sciences, Saiwaicho 3-5-8, Fuchu, Tokyo, 1838509, Japan. E-mail address: [email protected] (T. Yokoyama). http://dx.doi.org/10.1016/j.jenvrad.2016.04.011 0265-931X/© 2016 Elsevier Ltd. All rights reserved.

137 Cs on soil results in subsequent transfer to the terrestrial food chain due to its uptake by roots. The cesium content of plants is dependent on the absorption rate by roots and further translocation and redistribution from roots to above-ground plant parts (Sreenivasa et al., 2012). Hence, the development of safer crops must be a priority if radiocaesium-contaminated land is to be used for agricultural purpose (Hampton et al., 2004). Agricultural industries in Fukushima play an important role in Japan and are ranked fourth in the nation's producer of agricultural products. Therefore, in order to utilize Fukushima land for the safe production of agricultural products, research efforts must be directed towards the growing of crops that do not accumulate radioisotopes in their edible portions as a means of overcoming some of the current environmental problems in these areas. Cs accumulation by plants is a heritable trait (Payne et al., 2004). Selecting varieties of crop that display low accumulation of these

K.T. Win et al. / Journal of Environmental Radioactivity 158-159 (2016) 138e147

radionuclides has been suggested as an economically and socially acceptable remediation strategy for radiologically contaminated land (Penrose et al., 2015). For almost two decades, large efforts have been made to minimize the uptake of radiocaesium in the food chain by focusing the genetic differences in plant uptake of radiocaesium in some crops (Payne et al., 2004; Broadley and Willey, 1997; Kopp et al., 1990). In addition to differences in the accumulation of Cs between species, exploiting within species (inter-varietal) variation in uptake has also been proposed as a potential remediation strategy to produce less contaminated crops (White et al., 2003; White and Broadley, 2000; Prister et al., 1992). However, there are very limited numbers of data considering intraspecific variation on caesium translocation and it distribution in some leguminous plants (Win et al., 2015; Sreenivasa et al., 2012). Azuki bean (Vigna angularis) is one the five important cultigens of Genus Vigna, subgenus Ceratotropis, and widely cultivated in Japan, China and Korea. Azuki bean is the second most important legume in Japan after soybean. According to research findings Japan is supposed to be one possible place where azuki bean was domesticated (Kaga et al., 2008). Fukushima Prefecture is one of the leading azuki bean producing area, with the 4th largest production volume in Japan. However after the power plant accident, azuki production area was drastically decreased because it has a potential tendency to accumulate radiactive Cs to their seeds. In order to estimate the levels of radioactive Cs accumulation in azuki bean produced in Fukushima, it is important to obtain the actual data of Cs accumulation levels in edible portion (seeds) of azuki bean plants grown in the actual field in Fukushima Prefecture. We determined natural genetic variation in radiocaesium accumulating by mini-core collection of azuki bean accessions from Gene bank, Japan whether it is associated with morphological differences. This paper presents the first field evaluation of inter-varietal variation in the accumulation of 137Cs in azuki bean species in at actual field in Nakasato, Nihonmastu city, Fukushima shortly afterward FDNPP disaster in 2011. The objectives of this research were (1) to screen low and high absorption abilities of 137Cs from soil-to-seeds of azuki bean accessions and (2) to determine the relationships between seed Cs concentrations and some agronomic traits as a potential essential information for selecting and breeding ‘safer’ varieties. 2. Materials and methods 2.1. Field experiment Seeds of 97 azuki bean accessions were obtained from azuki

R¼

139

concentration 9.78 mmol*g
1. To determine the radiocaesium activity concentration of the soil, the soil was separately collected before sowing, the plot was divided into four sub-plots and the soil samples (15 cm in depth) were obtained from ten points (the corners and the center) from four plots. 137Cs concentration in soil was 3665 ± 480 Bq*kg
1. Nine plants of each accession were sown with 3 replicates, each plant being placed approximately 60 cm apart in mid-June 2012. For each replicate, the plot size was 5 m  5 m and the plots were arranged in a randomized complete block design. Local farmer practice was consistently performed in the studied areas and neither fertilizer nor pesticide was applied. Weeds were controlled by hand before flowering time. The recommended cultural practices were implemented throughout the crop seasons. Some agronomic characteristics such as time to flowering, time to maturity, total biomass, seed yield and 100 seed weight were measured or analyzed as mean from 3 replications (Table 4). Plant samples were harvested at full maturity (seed and shoot) and left for air drying before separating seed and shoot parts.

2.2.

137

Cs activity concentration and TF

After harvesting, the seeds were washed three times with distilled water to remove soil dust containing radioactive Cs. The air dried samples were crushed into powder by mortar and pestle. Then, the ground and homogenized samples was transferred into 20 ml plastic container (27 mm in diameter) and the specific activity was measured by Perkin Elmer 2480 Automatic Gamma counter WIZARD. The 137Cs activity of each sample was determined by counting gamma emissions for 1200 s. A mixed gamma standard solution (Amersham, QCY-46) was used for an efficiency correction and reference standard 137Cs solution and background was measured daily for an accuracy check. The TF provides information about the extent of accumulation in plants in comparison to the medium. The TF was determined using the following equation:

TF ¼


 Cs137 in seed Bq kg
1 dry weight
 Cs137 in soil Bq kg
1 dry weight

The radioactivity of the sample was corrected for the sampling date (September 16, 2012). For the calculation of TF, the radioactivity of soil was also corrected for the plant sampling date (September 16, 2012). To compare the differences in the accumulation of Cs between species, inter-cultivar variation (R) was calculated according to Penrose et al. (2015).

Concentration of element in the variety with the maximum concentration of that element Concentration of element in the variety with the minimum concentration of that element

mini-core collection in the National Institute of Agrobiological Sciences (NIAS). They were cultivated in the field of Nakasato, Nihonmatsu-city, in Fukushima prefecture in 2012 (Table 1). The field was disc ploughed and then harrowed and raked to obtain a good seed bed prior to soil sampling and sowing. The agrochemical parameters of composite sample of the surface soil from 0 to 15 cm were pH (water) 6.14, CEC 11.54 mEq*g
1, and available K

2.3. Data analysis For quantitative characteristics, data were assessed using simple statistics and numerical taxonomic techniques by cluster and principal component analyses with ‘Statistica’ and excel. Pearson product moment correlation analysis was done by using SigmaPlot 11.0 software (Systat Software, Inc., 2008).

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Table 1 List of the azuki bean accessions tested in this study. No.

Cultivar name

Scientific name

C1 C2 C3 C4 C6 C7 C9 C10 C11 C12 C13 C14 C15 C16 C17 C18 C20 C21 C22 C23 C24 C25 C26 C27 C28 C29 C30 C31 C32 C33 C34 C35 C36 C37 C38 C39 C40 C41 C42 C43 C44 C45 C46 C47 C48 C49 C50 C51 C52 C53 C54 C55 C56 C57 C58 C59 C60 C61 C62 C63 C64 C65 C66 C67 C68 C70 C71 C72 C73 C74 C75 C76 C77 C78

Akeazuki Kashiazuki Azuki Azuki Shiroazuki Azuki Azuki Shidareazuki Urumeazuki Nc91004 Shiroazuki Kurokawaazuki Okuazuki Azuki Waseazuki Azuki Azuki Kuroazuki Azuki Okameazuki Musumekitaka Waseazuki Musumekitaga Shiroazuki Kuroazuki Azuki Shiroazuki Shiroazuki Azuki Azuki Okukurozaya Nakateshirozaya Usugoromo Waseazuki Azuki Waseazuki Azuki Akiazuki Waseazuki Azuki Dainagon Azuki Waseazuki Azuki Azuki Shiroazuki Kuronboazuki Waseazuki Dainagon Waseazuki Okuazuki Azuki Azuki Azuki Azuki Azuki Natsuazuki Okuazuki Okuazuki Natsuazuki Dainagon Waseazuki Azuki Azuki Azuki Koazuki Azuki Azuki Dainagon Shiroazuki Akiazuki Ojiriazuki Mennohana Dainagon

Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna

angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis

(Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.) (Willd.)

Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi Ohwi

et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et et

Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi Ohashi

(¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus (¼Phaseolus

angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis) angularis)

JP number

Origin

81,501 81,502 81,510 103,811 76,495 85,365 85,369 85,370 76,591 104,244 220,118 76,497 76,498 76,588 76,470 76,483 76,490 72,999 73,085 76,459 76,464 76,467 76,468 76,475 76,479 73,084 72,987 73,011 73,006 73,096 72,990 73,007 72,995 73,099 208,696 211,711 211,722 211,733 219,277 219,291 219,315 73,098 73,102 103,405 103,439 103,442 104,214 104,217 213,461 213,440 213,444 90,825 90,830 110,307 110,304 110,324 110,330 110,337 110,338 110,354 85,376 87,809 81,481 81,483 81,488 81,515 81,520 201,407 201,351 201,381 201,433 201,414 201,415 201,419

Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan,

Status Aomori Aomori Aomori Iwate Iwate Iwate Iwate Iwate Akita Akita Akita Yamagata Yamagata Yamagata Fukushima Fukushima Fukushima Fukushima Fukushima Ibaraki Ibaraki Ibaraki Ibaraki Ibaraki Tochigi Tochigi Gunma Gunma Gunma Saitama Niigata Niigata Niigata Niigata Niigata Niigata? Niigata Niigata Ishikawa Ishikawa Ishikawa Nagano Nagano Nagano Nagano Nagano Nagano Nagano Gifu Aichi Aichi Mie Nara Nara Nara Wakayama Wakayama Wakayama Wakayama Wakayama Shimane Shimane Tokushima Kouchi Kouchi Nagasaki Nagasaki Kumamoto Ooita Ooita Ooita Miyazaki Miyazaki Miyazaki

Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace Landrace

K.T. Win et al. / Journal of Environmental Radioactivity 158-159 (2016) 138e147

141

Table 1 (continued ) No.

Cultivar name

Scientific name

C79 C80 W1 W2 W3 W4 W7 W8 W10 W12 W13 W14 W18 W21 W22 W23 W24 W25 W30 W31 W32 W33 W34

Azuki Akiazuki Ced97005 Ced2004-02c-01 Ced97018 Ced96101502 Ced97203 Ced96101604 Ced98001 Ced2001-29 Ced2001-106b Ced98083 Ced97078 Ced97042 Ced98015a Ced990034 Ced990039 Ced98100 Ced98019 Ced96111108 Ced98021 Ced98024 Ced98026

Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna Vigna

angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis angularis

Table 2 Pearson product moment correlation analysis of

Cs (Bq kg
1) in seed Total biomass (kg) Time to flowering Time to maturity Seed size (g)

137

137

(Willd.) Ohwi et Ohashi (¼Phaseolus angularis) (Willd.) Ohwi et Ohashi (¼Phaseolus angularis) var. nipponensis (Ohwi) Ohwi & Ohashi var. nipponensis (Ohwi) Ohwi & Ohashi var. nipponensis (Ohwi) Ohwi & Ohashi var. nipponensis (Ohwi) Ohwi & Ohashi var. nipponensis (Ohwi) Ohwi & Ohashi var. nipponensis (Ohwi) Ohwi & Ohashi var. nipponensis (Ohwi) Ohwi & Ohashi var. nipponensis (Ohwi) Ohwi & Ohashi var. nipponensis (Ohwi) Ohwi & Ohashi var. nipponensis (Ohwi) Ohwi & Ohashi var. nipponensis (Ohwi) Ohwi & Ohashi var. nipponensis (Ohwi) Ohwi & Ohashi var. nipponensis (Ohwi) Ohwi & Ohashi var. nipponensis (Ohwi) Ohwi & Ohashi var. nipponensis (Ohwi) Ohwi & Ohashi var. nipponensis (Ohwi) Ohwi & Ohashi var. nipponensis (Ohwi) Ohwi & Ohashi var. nipponensis (Ohwi) Ohwi & Ohashi var. nipponensis (Ohwi) Ohwi & Ohashi var. nipponensis (Ohwi) Ohwi & Ohashi var. nipponensis (Ohwi) Ohwi & Ohashi

JP number

Origin

85,354 85,361 90,833 225,126 90,835 87,908 90,869 87,911 110,658 211,817 211,827 110,683 90,854 90,838 110,664 201,460 201,465 110,686 110,666 108,493 110,668 110,669 110,670

Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan, Japan,

Status Kagoshima Kagoshima Miyagi Akita Yamagata Fukushima Chiba Niigata Yamanashi Nagano Nagano Shizuoka Wakayama Tottori Shimane Okayama Okayama Ehime Fukuoka Saga Nagasaki Nagasaki Nagasaki

Landrace Landrace Wild Wild Wild Wild Wild Wild Wild Wild Wild Wild Wild Wild Wild Wild Wild Wild Wild Wild Wild Wild Wild

Cs and plant growth parameters.

Total biomass (kg)

Time to flowering

Time to maturity

Seed size (g)

Seed yield (g)


0.376**


0.35** 0.55**


0.288** 0.569** 0.893**


0.0455ns 0.482**
0.0656ns
0.0231ns


0.274* 0.731** 0.244* 0.291* 0.521**

Table 3 Estimation of genetic parameters of some agronomic traits and

137

Cs concentration in seeds among 97 azuki bean accessions.

Characters

Mean range

PCV (%)

GCV (%)

Broad sense heritability (%)

Total biomass (g) Seed weight (g) Time to flowering Time to maturity 100 seed weight (kg) 137 Cs concentration in seeds (Bq kg
1)

40e395 6.8e69.9 59e116 90e153 1.6e23.5 3.4e33.7

50.86 20.83 12.04 11.93 12.29 44.54

47.97 20.09 12.02 11.27 12.27 39.44

88 92 98 89 79 78

Genetic parameters for each trait were estimated by using the following formulae (Singh and Chaudhary, 1977);

   .  2 Broad sense heritability h2 % ¼ dg d2p

Genotypic coefficient variation ðGCV %Þ   genetic variance d2g x 100 ¼ total mean value ððxÞ

3. Results and discussions

Phenotypic coefficient variation ðPCV %Þ   2 phenotypic variance dp ¼ x 100 total mean value ððxÞ     Phenotypic variance d2p ¼ genotypic variance d2g

  2 þ environmental variance de

3.1. Cluster analysis based on agronomic traits Nighty seven azuki bean genotypes obtained from azuki minicore collection in NIAS were evaluated on yield and yield components in relation to phenological characteristics (Table 4). Growth period of the genotypes ranged from 90 to 153 days. Based on the days to maturity, the genotypes were grouped into early, medium and late. Flowering period was between 59 and 116 days. There were large variations among the genotypes for seed yield per plant (6.8 ge69.9 g). The UPGMA (Unweighted Pair Group Method with Arithmetic Mean) cluster analysis revealed three main groups, A, B and C (Fig. 1). Group A consisted of 3 sub-clusters of 67 accessions. Sub-

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Table 4 Mean values for agronomic parameters used in the UPGMA cluster analysis. Cultivars

Total biomass plant
1 (g)

Time to flowering (day)

Time to maturity (day)

100 seed weight (g)

Seed yield plant
1 (g)

C1 C2 C3 C4 C6 C7 C9 C10 C11 C12 C13 C14 C15 C16 C17 C18 C20 C21 C22 C23 C24 C25 C26 C27 C28 C29 C30 C31 C32 C33 C34 C35 C36 C37 C38 C39 C40 C41 C42 C43 C44 C45 C46 C47 C48 C49 C50 C51 C52 C53 C54 C55 C56 C57 C58 C59 C60 C61 C62 C63 C64 C65 C66 C67 C68 C70 C71 C72 C73 C74 C75 C76 C77 C78

72.4 106.7 91.2 116.3 224.8 78.3 107.5 146.2 83.8 81.0 141.3 161.3 126.3 221.2 74.3 233.0 59.0 142.7 40.5 161.5 171.0 152.0 123.7 163.3 115.6 147.2 159.3 216.0 249.6 202.3 220.0 266.5 248.5 68.4 249.7 127.4 269.0 140.0 209.8 228.8 239.2 209.8 156.5 370.5 288.5 320.4 251.4 217.6 279.8 51.0 134.6 195.8 188.0 236.4 230.0 318.5 40.0 390.8 286.8 44.0 239.0 137.7 180.8 371.4 283.0 129.4 285.6 260.6 152.8 199.0 186.4 232.6 254.4 395.2

59 62 65 76 86 88 65 65 72 76 83 65 83 65 65 65 65 72 65 83 87 65 83 91 83 76 92 92 92 92 88 88 83 65 84 72 86 83 92 92 86 86 86 92 92 92 92 86 94 65 83 92 97 88 110 102 62 107 114 62 88 87 90 112 91 107 94 89 91 116 90 90 92 113

99 101 98 99 130 122 108 97 104 106 111 104 110 106 97 97 96 108 93 109 117 93 111 119 110 107 123 125 125 122 113 116 115 90 110 103 130 116 116 120 114 114 109 123 120 120 118 120 125 93 111 123 131 119 140 138 97 140 151 93 126 109 138 151 153 145 131 119 109 152 135 123 118 142

11.5 14.3 14.5 15.0 7.0 14.5 17.5 16.0 13.5 11.5 5.5 14.5 15.0 11.5 13.3 15.0 13.0 14.0 10.0 13.5 15.0 10.0 11.5 16.0 16.0 11.6 15.5 9.0 20.5 17.5 15.0 19.0 19.5 10.5 15.5 10.0 17.0 15.0 10.5 23.5 17.5 11.5 15.0 21.0 16.0 15.0 9.5 9.0 22.5 10.5 13.5 14.5 21.0 16.0 16.0 10.0 11.0 10.0 10.0 8.5 17.0 15.5 20.0 15.0 21.0 14.0 10.5 17.5 17.9 11.5 18.0 23.0 20.0 23.5

42.4 44.4 44.4 47.5 55.8 56.1 47.7 44.5 47.4 48.4 50.1 45.9 51.8 45.7 43.8 44.3 43.5 48.8 42.0 50.2 54.8 42.0 51.4 56.5 52.0 48.7 57.7 56.6 59.4 57.9 54.1 55.8 54.4 41.4 52.2 46.3 58.3 53.5 54.7 58.9 54.4 52.9 52.5 59.1 57.1 56.8 54.9 53.8 60.4 42.1 51.9 57.4 62.3 55.8 66.6 62.6 42.5 64.3 68.8 40.9 57.8 52.9 62.0 69.6 66.3 66.5 58.9 56.4 54.5 69.9 60.8 60.1 57.6 69.7

K.T. Win et al. / Journal of Environmental Radioactivity 158-159 (2016) 138e147

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Table 4 (continued ) Cultivars

Total biomass plant
1 (g)

Time to flowering (day)

Time to maturity (day)

100 seed weight (g)

Seed yield plant
1 (g)

C79 C80 W1 W2 W3 W4 W7 W8 W10 W12 W13 W14 W18 W21 W22 W23 W24 W25 W30 W31 W32 W33 W34

261.6 327.2 74.0 69.0 70.8 68.0 109.3 83.4 127.7 145.7 95.0 82.0 60.8 110.3 131.0 86.4 127.0 159.6 113.0 153.5 134.4 135.0 95.5

92 115 76 86 86 100 90 89 83 89 88 92 92 88 86 91 100 100 107 97 107 100 92

134 150 110 119 126 124 123 133 121 121 124 122 102 119 119 124 127 130 130 129 130 129 122

15.0 6.5 2.2 1.9 2.1 2.2 1.7 2.5 2.2 1.9 2.1 1.8 1.8 2.1 1.9 3.3 2.2 2.0 2.3 2.4 1.6 1.9 1.9

60.3 68.0 14.0 19.4 10.9 6.8 17.3 18.9 27.8 21.0 26.4 9.9 10.3 25.9 14.4 25.6 21.1 16.6 23.7 25.0 34.9 17.0 17.1

cluster A-1 composed of 22 accessions showing early maturity (93e108 days) and low yield (between 40 and 50 g plant
1). Origin of almost all of the accessions from group A-1 were Tohoku region. Regarding 40 accessions grouped in sub-cluster A-2, all were early to medium maturity (109e130 days) and medium yield (between 50 and 60 g plant
1). Sub-cluster A-3 composed of 5 accessions showing medium maturity (131e138 days) and high yield (between 60 and 70 g plant
1). In groups A-2, A-3, the accessions

were grouped irrespective of their origin. The group B composed of 21 accessions of wild relatives showing early to medium maturity (102e130 days) and the lowest yield (between 34.9 and 6.8 g plant
1). Nine accessions showing late maturity (140e153 days) with the high yield (66e70 g plant
1) were grouped in main group C. The accessions of group C were origin from western part of Japan such as Kansai, Shikoku, Kyushu regions. The extent of genetic variability of a quantitatively inherited trait and the manner of its

Fig. 1. Dendrogram of 97 accessions of azuki bean based on 5 agronomic characters: Group A1-genotypes having early maturity and low yield, A2-genotypes having early maturity and medium yield, A3-genotypes having medium maturity and high yield, B-genotypes having medium maturity and low yield (wild relatives) and C-genotypes having late maturity with high yield.

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inheritance determines its usefulness in plant improvement. The morphological characterization is useful to characterize Vigna accessions based on yield component traits (Win et al., 2009). Shinano et al. (2014) stated that the difference in the growth behavior is an important characteristic considering the plant capacity to absorb non-essential elements from the environment. In order to know how the agronomic characteristics influence on the uptake of 137Cs in plants, we compared the 137Cs activity

concentration in seeds of 97 azuki bean accessions along with their groups of agronomic traits. 3.2. Variation of the 137Cs concentration in seeds among azuki bean accessions Inter- and intra-specific variations in radiocaesium (137Cs) activity concentrations in seed portions of 97 azuki bean accessions

Fig. 2. Comparison of radiocaesium (137Cs) activity concentrations in edible portions of 97 azuki beans of the azuki mini-core collection belonging to each morphological group. The numbers given correspond to the cultivars shown in Table 1.

K.T. Win et al. / Journal of Environmental Radioactivity 158-159 (2016) 138e147

Fig. 3. Average transfer factors values (TF) of

145

137

Cs for edible portions (seeds) of 97 azuki bean accessions.

were shown along with their groups of agronomic traits (Fig. 2). In group A-1, radiocaesium (137Cs) activity concentrations in seeds were ranged from 5.1 to 33.7 Bq kg
1. Those were ranged from 6.5 to 25.0 Bq kg
1 and from 6.6 to 23.5 Bq kg
1 in group A-2 and A-3, respectively. In group B, those were ranged from 4.5 to 25.0 Bq kg
1 of seeds. The radiocaesium (137Cs) activity concentrations ranged from 3.4 to 13.8 Bq kg
1 of seeds in group C. Among 97 azuki bean accessions, the cultivar C74 (3.4 Bq kg
1) from group C showed the lowest radiocaesium (137Cs) activity concentrations in seeds whereas the cultivar C21 (33.7 Bq kg
1) from group A-1 showed the highest. According to passport data of

NIAS, Japan, the origin of cultivar C74 was at Ooita prefecture, in northern part of Kyushu, and that of C21 was from Fukushima prefecture. Notably, these differences observed under field conditions can also be caused by the uneven distribution of 137Cs in the field; in the observed difference, highest value of radiocaesium (137Cs) activity concentrations in a soil was 1.3 times higher than the value of the lowest soil (range between 4077 and 3100 Bq kg
1). However, variations of radiocaesium (137Cs) activity concentrations in seeds showed around 10 times differences at radiocaesium (137Cs) activity concentrations among the lowest accumulator and the highest one, suggesting a wide variation in 137Cs concentration

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among azuki bean accessions. In our study, the differences in 137Cs activity accumulation by seeds were observed by the difference in seed yield. The dilution effect, which indicates that the accumulated non-essential element content is diluted by the accumulated biomass, is sometimes mentioned (Jarrell and Beverly, 1981). Our studies confirmed that the lowest 137Cs activity accumulator was C74 and it showed the high yield (69.9 g plant
1) whereas the highest 137Cs activity accumulator was C21 exhibited the low yield (48.79 g plant
1) among the investigated accessions (Table 4). The C21 variety accumulating 90% higher 137Cs (Bq kg
1 dry weight basic) than C74, but showed a productivity which was only 30% lower than that of C74. Intra-species variation in radiocaesium (137Cs) activity accumulation was recently reviewed by Penrose et al. (2015). Intervarietal variation was expressed at the ratio of the maximum to minimum observed concentrations for a given crop species and R values for cultivar [Vigna angularis (Willd.) Ohwi et Ohashi (¼Phaseolus angularis)] and wild relative (Vigna angularis var. nipponensis (Ohwi) Ohwi & Ohashi) were 10 and 3.4, respectively (Fig. 4). This variation suggests that exploitation of inter-varietal variation could be used in some crop species to reduce the transfer of these radionuclides to a similar extent to existing remediation strategies. These results showed that C74 variety has the lowest 137 Cs accumulation ability, suggesting that this variety is suitable for further breeding for lower radiocaesium (137Cs) activity accumulation in seeds. Twinning et al. (2004) and Waegeneers et al. (2001) proposed that the genetic differences in the uptake of radiocaesium by crops can be influenced by differences in productivity, the extent of radionuclide accumulation are different from both between and within plant species. Thus, it is a need to determine how the agronomic characteristics influence on accumulation of radiocecium (137Cs) activity concentration in seeds of investigated azuki bean accessions.

reported that the greater the biomass, the lower the 137Cs concentration due to the dilution (Fritioff et al., 2005; Ekvall and Greger, 2003). Shinano et al. (2014) also reported similarly; a close relationship found between the dry weight and radiocaesium content in the genus Amaranthus; where the author discussed that the dilution effect can partly explain the difference in radiocaesium uptake ability among different species or varieties. There was a negative strong correlation between maturity period and 137Cs activity concentration in seed. This suggested that cultivars showing late maturity in crop performances had a tendency as a low accumulator of 137Cs activity concentration in seeds while early variety may absorb radiocecium (137Cs) more during its fast growing period and complete its crop cycle with low biomass compared to late maturity variety. In the other hands, low 137Сs concentration of late maturity with high yield groups may be caused either by lower 137Cs uptake rate due to its slower growth at the early growing period, or by biological dilution effect due to its high rate of biomass gain at the later growing period (Ulyanenko et al., 2002). Natural genetic variation in ionomic uptake was observed in selected populations of Arabidopsis thaliana where author suggested that the variation observed in the accumulation of most elements between shoots and seeds may be attributed to the large differences in the biochemical and physiological functions of these tissues including root system (Buescher et al., 2010). Genotype dependency of specific uptake were studied in phosphate accumulation in seed and shoot (Gahoonia and Nielsen, 2004; Bentsink et al., 2003), and shoot cesium (Cs) accumulation (Payne et al., 2004). The correlation analyses reported here suggest that, as a general prediction for plants with unknown uptake, early maturity plants with low biomass will become contaminated at the highest radiocaesium (137Cs) activity concentration in their edible portion whilst late maturity plants with a high biomass of the lowest activity.

3.3. Correlation between 137Cs activity concentration and agronomic characteristics

3.4. Genetic parameters

137

To confirm whether plant growth characteristics influence Cs activity accumulation in seed portion, we analyzed the pearson product moment correlation analysis of 137Cs (Bq kg
1 of seed dry weight) and plant growth parameters (Table 2). The 137Cs activity concentration was negatively correlated with total biomass (kg), at 1% significant level and seed yield (g) at 5% level. It has been

Inter-cultivar variation (R) in 137Cs accumulation in seeds

12 10 8 6 4 2 0 Species 137

Fig. 4. Inter-varietal variation (R) in Cs accumulation by 76 accessions of azuki bean cultivars [(Vigna angularis (Willd.) Ohwi et Ohashi (¼Phaseolus angularis)] (black bar) and 21 accessions of wild relatives (Vigna angularis var. nipponensis (Ohwi) Ohwi & Ohashi) (white bar).

The estimation of genetic parameters of some agronomic traits and 137Cs concentration in seeds among 97 azuki bean accessions are given in Table 3. High genotypic coefficient of variation (GCV %) and phenotypic coefficient of variation (PCV %) were observed in total biomass and 137Cs concentration in seeds. In the present study, heritability was high (greater than 75%) for all studied traits. These results suggested that the environmental factors had a small effect on the inheritance of traits with high heritability. The higher value of heritability means more heterogeneous and higher variability of the population and indicates that selection based on mean would be successful in improving these traits (Win et al., 2011). For example, Kanter et al. (2010) reported genetic variation for shoot Cs concentration among 86 worldwide accessions of Arabidopsis and succeeded in detecting several QTLs for Cs accumulation using an F2 population from a cross between high and low Cs-accumulating accessions. Until now, two linkage mapping approaches were carried out for Csþ accumulation in different RIL populations from Arabidopsis thaliana (White et al., 2003; Payne et al., 2004). These results highly suggest that there is genetic variation for seed Cs concentration in azuki bean germplasm and these information were a valuable approach to identifying genes associated with Cs accumulation. 3.5. Soil-to-seed

137

Cs TF

The transfer of 137Cs from soil to edible portion (seeds) is process which plays an important role in the soil-edible portion-human pathway. Therefore, it is necessary to compare not only the absolute

K.T. Win et al. / Journal of Environmental Radioactivity 158-159 (2016) 138e147

value of the accumulated radiocaesium but also the ratio of radiocaesium transported from the soil. The ratio of the lowest TF to the highest TF was approximately 10. As commonly observed (Bell et al., 1988), the transfer of 137Cs from soil to plants was affected as much by species-specific differences in uptake. Variations in radiocaesium soil-to plant transfer have been reported among and within plant species (Payne et al., 2004; Frissel et al., 2002) supporting the influence of plant genotype in radiocaesium uptake (Buysse et al., 1996). The results indicate that certain varieties have higher levels of accumulated radiocaesium and TF. The highest TF was found in C21 (0.092) and the lowest was in C74 (0.009) (Fig. 3). 4. Conclusion The results presented here suggest that certain varieties of azuki bean accumulate less 137Cs into the seeds than others that are officially adopted and used in normal agricultural practice. This research exhibited a significant varietal difference in the biomass production, radiocaesium accumulation and transfer factor (TF) of radiocaesium from the soil to edible portion. The reproducibility of inter-varietal variation between sites and growing seasons should be the focus of future research. In addition, it was approved that different accumulation patterns among the azuki bean accessions depends on their growth performance by showing strong negative relationship between 137Cs concentration in their edible portions and either of total biomass or time to maturity. With the use of those information, these cultivars with different Cs accumulation may lead to the identification of genes that regulate Cs transport and accumulation in azuki bean for future molecular biological approach such as QTL-Seq described by Takagi et al. (2013). Acknowledgements This study was supported by the Special Research Fund of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan titled “Research and development of security and safe crop production to reconstruct agricultural lands in Fukushima Prefecture based on novel techniques to remove radioactive compounds using advanced bio-fertilizer and plant protection strategies”. This work was also supported by a Grant-in-Aid for Scientific Research (B):24380176 from the Japan Society for the Promotion of Science (JSPS). References Bell, J.N.B., Minski, M.J., Grogan, H.A., 1988. Plant uptake of radionuclides. Soil Use Manag. 4, 76e84. Bentsink, L., Yuan, K., Koorneef, M., Vreugdenhil, D., 2003. The genetics of phytate and phosphate accumulation in seeds and leaves of Arabidopsis thaliana, using natural variation. Theor. Appl. Genet. 106, 1234e1243. Broadley, M.R., Willey, N.J., 1997. Differences in root uptake of radiocaesium by 30 plant taxa. Environ. Pollut. 95, 311e317. Buescher, E., Achberger, T., Amusan, I., Giannini, A., Ochsenfeld, C., Rus, A., Lahner, B., Hoekenga, O., Yakubova, E., Harper, J.F., Guerinot, M.L., Zhang, M., Salt, D.E., Baxter, I.R., 2010. Natural genetic variation in selected populations of Arabidopsis thaliana is associated with ionomic differences. PLoS One 5 (6), e11081. http://dx.doi.org/10.1371/journal.pone.0011081. Buysse, J., Van de Brande, K., Merckx, R., 1996. Genotypic differences in the uptake and distribution of radiocaesium in plants. Plant Soil 178, 265e271. Ekvall, L., Greger, M., 2003. Effects of environmental biomass-producing factors on Cd uptake in two Swedish ecotypes of Pinus sylvestris. Environ. Pollut. 121, 401e411. Frissel, M.J., Deb, D.L., Fathony, M., Lin, Y.M., Mollah, A.S., Ngo, N.T., Othman, I., lu, S., Twining, J.R., Uchida, S., Robison, W.L., Skarlou-Alexiou, V., Topcuog

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