Open access peer-reviewed chapter

Breeding of Rj Gene-Accumulated Soybean Genotypes and Their Availability for Improving Soybean Productivity

Written By

Sokichi Shiro and Yuichi Saeki

Submitted: 03 January 2022 Reviewed: 24 January 2022 Published: 22 March 2022

DOI: 10.5772/intechopen.102833

From the Edited Volume

Soybean - Recent Advances in Research and Applications

Edited by Takuji Ohyama, Yoshihiko Takahashi, Norikuni Ohtake, Takashi Sato and Sayuri Tanabata

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Abstract

Some soybean varieties harbor the Rj genes, which regulate nodulation by preventing infection and nodulation by specific rhizobial strains. Soybean genotypes carrying several Rj genes may enhance the occupancy of useful bradyrhizobia, which exhibit potent nitrogen fixation ability and exhibit nodulation compatible with the Rj genotype of soybean. Therefore, we bred soybean lines presenting the Rj2Rj3Rj4 genotype by crossing the Japanese cultivars “Bonminori” (Rj2Rj3) and “Fukuyutaka” (Rj4) and studied the effects of Rj gene accumulation on productivity. To investigate yield components, three Rj gene-accumulated soybean lines (B × F − E, B × F − M, and B × F − L) and three soybean cultivars (“Enrei,” “Sachiyutaka,” and “Fukuyutaka”) were cultivated in 2016 and 2017. Pod and seed number and yield were the highest in B × F − M. The occupancy rate of isolates in cluster of Bradyrhizobium diazoefficiens USDA 110T carrying the hydrogen uptake genes tended to be lower in the Rj2Rj3Rj4 soybean lines than in “Sachiyutaka” and “Fukuyutaka.” Additionally, the occupancy rate of this cluster was positively correlated with yield. Therefore, promoting infection by bradyrhizobial strains carrying the hydrogen uptake genes may improve soybean productivity. Moreover, the Rj2Rj3Rj4 genotype of soybean may be inoculated with B. diazoefficiens USDA 110T, which is not restricted by the Rj2 gene, to further enhance soybean productivity.

Keywords

  • soybean
  • Rj gene
  • breeding
  • yield components
  • infection tendency

1. Introduction

Soybean (Glycine max (L.) Merr.) is one of the most important legume crops in the world, including Japan. According to the information on soybean production and consumption published by the Japanese Ministry of Agriculture, Forestry and Fisheries (MAFF), soybean yield in the country is 166 kg 10 a−1, which is lower than those in major producing countries, including the United States (358 kg 10 a−1), Brazil (342 kg 10 a−1), Argentina (309 kg 10 a−1), and China (188 kg 10 a−1) [1]. To improve this lower productivity, breeding of high-yielding soybean and improvement of cultivation techniques, such as pest control, field management, and plantation methods, have been extensively studied. One of the cultivation techniques is the inoculation of rhizobia, which exhibit potent nitrogen-fixing capacity, during soybean plantation.

As a leguminous plant, soybean roots bear nodules formed as a result of infection by nodulating rhizobia, which perform symbiotic nitrogen fixation, and the plant acquires atmospheric nitrogen in the form of ammonia through these root nodules. Major soybean-nodulating rhizobia include Bradyrhizobium japonicum, Bradyrhizobium diazoefficiens, Bradyrhizobium elkanii, and Sinorhizobium (=Ensifer) fredii [2, 3, 4, 5, 6, 7]. In addition to these, Bradyrhizobium yuanmingense, Bradyrhizobium liaoningense, Sinorhizobium xinjiangense, and Mesorhizobium tianshanense have been reported as soybean-nodulating rhizobial species [8, 9, 10, 11, 12, 13, 14]. B. diazoefficiens USDA 110T is a symbiont possessing a hydrogen uptake (Hup) system that recycles H2 produced as a by-product of nitrogenase activity, thereby increasing nitrogen fixation efficiency [15, 16, 17]. The inoculation of bradyrhizobia possessing this system, such as B. diazoefficiens Hup+ strains, enhances the productivity of legume crops [18]. However, the efficiency of inoculated rhizobia with high nitrogen fixation ability remains poor in the field, because they cannot compete with indigenous soybean-nodulating rhizobia in the soil. To solve this problem, the ecology of indigenous soybean-nodulating rhizobia in terms of genetic diversity and compatibility with the host soybean must be elucidated.

Rj or rj are the well-known host genes that regulate soybean nodulation, and non-Rj, rj1, Rj2, Rj3, Rj4, and Rfg1 genotypes of soybean have been confirmed to exist naturally [19, 20, 21, 22, 23, 24]. In addition to these, Rj genotypes, including rj5, rj6, and rj7, have been developed through experimental mutagenesis [25, 26, 27, 28, 29, 30, 31]. The Rj2, Rj3, Rj4, and Rfg1 genotypes are known to restrict nodulation by specific strains of Bradyrhizobium or Sinorhizobium species. Meanwhile, the Rj2, Rj3, Rj4, and Rfg1 genotypes restrict nodulation by B. diazoefficiens USDA 122, B. elkanii USDA 33, B. elkanii USDA 61, and Sinorhizobium fredii USDA 257. Furthermore, B. japonicum Is−1 and Is−34 exhibit incompatibility with the Rj2 and Rj4 genotypes, respectively [32]. The rj1, rj5, and rj6 genotypes restrict nodulation by all soybean-nodulating rhizobial strains. The rj7 genotype developed through ethyl methane sulfonate (EMS)-induced mutagenesis is a “hypernodulation” genotype, which can form abundant nodules [33]. The Rj2/Rfg1 gene encodes a member of the Toll-interleukin receptor–nucleotide-binding site–leucine-rich repeat (TIR–NBS–LRR) class of plant resistance (R) proteins, which confer resistance against microbial pathogens through an effector-triggered immune (ETI) response [34]. Furthermore, the amino acid determinant of the Rj2 genotype in cultivated and wild soybeans has been reported [35]. The Rj4 gene encodes a thaumatin-like protein (TLP), classified as pathogenesis-related protein 5 (PR5). PR proteins are induced by pathogen attack and involved in host resistance [36, 37]. In addition, the type III secretion system (T3SS) structural gene in B. elkanii USDA 61 and B. japonicum Is−34 is involved in the restriction of nodulation in the Rj4 genotype of soybean [38, 39].

The compatibility and preference for nodulation by bradyrhizobial strains of soybean cultivars and varieties exhibiting the Rj genotype have been investigated [32], and the Rj2Rj3Rj4 genotype lines, in which the Rj genes are accumulated, have been bred by crossing the soybean cultivars “IAC-2” (Rj2Rj3) and “Hill” (Rj4) [40]. The Rj2Rj3Rj4 genotype is superior to the non-Rj, Rj2Rj3, and Rj4 genotypes in terms of the efficiency of nodulation by inocula with potent nitrogen fixation ability [41]. In addition, the community structure of indigenous soybean-nodulating bradyrhizobia was significantly different across five Rj genotypes (non-Rj, Rj2Rj3, Rj3, Rj4, and Rj2Rj3Rj4) [42]. Furthermore, the Rj2Rj3 and Rj2Rj3Rj4 genotypes presented a higher occupancy of the indigenous soybean-nodulating bradyrhizobial cluster of B. diazoefficiens USDA 110T than the non-Rj, Rj3, and Rj4 genotypes, regardless of the cultivation temperature [43]. Thus, the availability of the Rj2Rj3Rj4 genotype of soybean has been reported. Since the Rj2Rj3Rj4 genotype of soybean has been produced by crossing foreign cultivars, Rj gene-accumulated soybean cultivars that match the needs of Japanese consumers and producers must be developed. Therefore, we bred the Rj2Rj3Rj4 genotype of soybean by crossing the Japanese soybean cultivars “Bonminori” (Rj2Rj3) and “Fukuyutaka” (Rj4). According to the information on the development and diffusion of new soybean cultivars published by the Japanese MAFF, “Fukuyutaka” is the most cultivated soybean cultivar in the country [44], and this cultivar was registered in 1980 [45].

In this chapter, we describe breeding and selection processes, shoot growth, yield components, and infection tendency of useful bradyrhizobia of Rj gene-accumulated soybean genotypes produced by crossing Japanese cultivars.

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2. Breeding and selection of Rj gene-accumulated soybean

2.1 Phenotypic analysis of “Bonminori” × “Fukuyutaka” F3 seeds

To select Rj gene-accumulated soybean lines with the Rj2Rj3Rj4 genotype, 157 F3 seeds from the experimental field of the Faculty of Agriculture, University of Miyazaki (31°49′41″N, 131°24′45″E), were subjected to the inoculation test. B. japonicum Is−1 and B. japonicum Is−34, which exhibit incompatibility with the Rj2 and Rj4 genotypes of soybean, respectively, were used as the inoculum strains. The strains were cultured in 1 mL of HEPES-MES (HM) medium [46] supplemented with 0.1% l-arabinose [47] for 3–5 days in the dark at 28°C. The bacterial cultures were then diluted with sterile distilled water to 106 cells mL−1 and mixed with the respective strain. Culture pots (1 L) were filled with vermiculite containing aqueous N-free nutrient solution (40% v/v) [48] and autoclaved at 121°C for 20 min. F3 seeds were sterilized using 70% ethanol for 30 s and diluted sodium hypochlorite solution (0.25% available chlorine) for 3 min and then washed with sterile distilled water. Five seeds of each line were sown per pot, inoculated with 1 mL of diluted bacterial culture per seed, and cultivated for 3–4 weeks in a growth chamber (day, 28°C for 16 h; night, 25°C for 8 h), with weekly supply of sterile distilled water. After cultivation for 3–4 weeks, the presence or absence of nodulation on soybean roots was observed.

2.2 Selection of non-nodulation phenotype using the inoculation test

Theoretically, all F1 lines obtained by crossing “Bonminori” and “Fukuyutaka” should present the Rj2Rj2Rj4Rj4 genotype, and according to Mendel’s law, the probability of F2 lines exhibiting this genotype is 1/16. In the F3 lines, individuals with the Rj2Rj2Rj4Rj4 genotype can be obtained by self-fertilization of F2 individuals with the Rj2rj2Rj4Rj4, Rj2Rj2Rj4rj4, and Rj2rj2Rj4rj4 genotypes. To select individuals with the Rj2Rj2Rj4Rj4 genotype, we subjected 153 lines of F3 seeds, excluding four lines of seeds that had decayed during storage in the refrigerator, to inoculation test. The appearance of soybean roots during the inoculation test is shown in Figure 1. Dominant homozygous plants, such as those with the Rj2Rj2Rj4Rj4 genotype, did not form root nodules (Figure 1a). We proceeded with the screening based on this phenotype and selected eight lines from the 153 lines (Table 1). These eight lines were grown for several years. Three plants differing in terms of the flowering and ripening periods by approximately 1 week each were detected and selected for further cultivation.

Figure 1.

Appearance of nodulation following the inoculation of Bradyrhizobium japonicum Is−1 and Is−34. Soybean roots with (a) and without (b) nodulation restriction.

Phenotypes of F3 seedsNumber of soybean lines
non-nodulation8
non-nodulation or nodulation63
nodulation82
not tested4
Total157

Table 1.

Nodulation phenotypes of F3 seeds.

Among the five seeds sown for selection, lines that did not form root nodule on all plants were classified as “non-nodulation,” lines that formed root nodule more than one of the five plants were classified as “non-nodulation or nodulation,” and lines that formed root nodule all plants classified as “nodulation.”

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3. Evaluation of shoot growth and yield components of Rj gene-accumulated soybean

3.1 Experimental site, design, and tested soybean variety

A 2-year field trial was conducted in 2016 and 2017 in the experimental field of the Agricultural Science Section, Education and Research Center for Biological Resources, Faculty of Life and Environmental Science, Shimane University, Japan (35°30′55″N, 133°06′36″E). The experimental sites were located at 35°30′60″N, 133°06′35″E in 2016 and 35°31′02″N, 133°06′40″E in 2017. Both experimental fields had gray lowland soil (paddy conversion fields). Soil pH (H2O) and electrical conductivity (mS cm−1) were respectively 6.42 and 0.10 in 2016 and respectively 6.72 and 0.06 in 2017. Before sowing, nitrogen, potassium, and phosphorus were applied at doses of 40, 100, and 100 kg ha−1, respectively. To correct soil pH, magnesium lime was applied at the dose of 1000 kg ha−1. The experiment followed the split-plot design with three replicates. Three soybean cultivars, namely “Enrei,” “Sachiyutaka,” and “Fukuyutaka,” as well as F10 or F11 plants of three Rj gene-accumulated soybean lines with different flowering and ripening periods, namely B × F − E, B × F − M, and B × F − L, were tested. “Enrei” and “Sachiyutaka” were registered in 1971 and 2001, respectively [45]. “Enrei” presents the rj4 genotype [37]. “Sachiyutaka” may present the Rj4 genotype, because it is bred through backcrossing “Enrei” with F2 plants from a cross “Enrei” and “Fukuyutaka” [45]. All soybean seeds were sown at a depth of 3–4 cm on June 20, 2016, and June 21, 2017, respectively, and the planting density was 11.1 and 10.1 plants m−2 in 2016 and 2017, respectively.

3.2 Data collection and analysis

Soybean growth was evaluated during the flowering and harvest periods. Samples were collected by from 10 consecutive plots per replicate. During the flowering period, plant height, node number, branch number, stem and leaf dry weight, and main culm dry weight (2017 only) were measured. During the harvest period, plant height, node number, shoot dry weight, pod number, seed number, 100-seed weight, and yield were measured. Plant dry weight was measured after drying at 70°C for over 72 h in a drying apparatus. All statistical analyses were performed using R version 4.0.3 [49]. Soybean growth parameters during the flowering period were analyzed using Tukey’s honestly significant difference (HSD) test for multiple comparisons using the R package “multcomp.” Soybean yield components were subjected to two-way analysis of variance using anovakun version 4.8.5 [50]. Meteorological data during soybean cultivation were collected from past information provided by the Japan Weather Association (Table 2).

YearmonthTemperature (°C)Precipitation Sunshine
minimummaximummean(mm)duration (h)
2016Jun.19.026.822.3166.04.9
Jul.23.530.826.677.05.7
Aug.23.632.227.2140.57.7
Sep.20.726.723.3293.02.8
Oct.15.322.318.5103.53.5
Nov.8.816.212.2120.03.2
2017Jun.16.525.920.986.57.3
Jul.24.831.527.6168.55.6
Aug.24.431.527.4141.56.8
Sep.18.526.322.1214.54.9
Oct.14.321.017.5358.03.6
Nov.6.715.711.193.04.6

Table 2.

Meteorological data during soybean cultivation in 2016 and 2017.

Values indicate monthly averages, and each value was calculated based on meteorological data provided by the Japan Weather Association.

3.3 Growth and yield of Rj gene-accumulated soybean

The results of soybean growth during the flowering period in 2017 are presented in Table 3. The measurements during the flowering period were conducted on August 10, 2017, for B × F − E and “Enrei”; August 17, 2017, for B × F − M and “Sachiyutaka”; and August 26, 2017, for B × F − L and “Fukuyutaka.” The plant height of Rj gene-accumulated soybean lines tended to increase in the order B × F − E < B × F − M < B × F − L, indicating dependence on the lateness of the flowering period. Similarly, the plant height of other soybean cultivars tended to increase in the order of “Enrei” < “Sachiyutaka” < “Fukuyutaka,” indicating dependence on the lateness of the flowering period. Branch number was the highest in “Fukuyutaka” and the lowest in “Enrei.” In addition, among the Rj gene-accumulated soybean lines, plant height tended to be higher in B × F − L than in the other lines, although the difference was not significant. There were no significant differences in shoot dry weight among the cultivars, although “Fukuyutaka,” B × F − M, and “Enrei” showed higher values in that order.

CultivarPlant height (cm plant−1)Node number (No. plant−1)Branching number (No. plant−1)Main culm dry weight (g m−2)Stem and leaf dry weight (g m−2)Shoot dry weight (g m−2)
BxF–E66.2 ab13.56.1 ab13.023.136.1
BxF–M67.9 ab13.16.5 ab15.325.140.4
BxF–L74.9 b13.67.2 bc16.722.439.0
Enrei53.7 a11.54.5 a12.227.039.2
Sachiyutaka57.3 a12.36.4 ab12.722.635.4
Fukuyutaka64.5 ab12.29.2 c17.423.841.2
ANOVA*ns***nsnsns

Table 3.

Growth of soybean cultivars during the flowering period in 2017.

Values are presented as the means of three replicates. *p < 0.05, ***p < 0.001, and ns = not significant. Different letters indicate significant differences (Tukey’s HSD test) at p < 0.05 for different soybean cultivars.

The results of yield components of soybean cultivars during the harvest period in 2016 and 2017 are presented in Table 4. In ANOVA, all yield components, except 100-seed weight, significantly differed between years and among cultivars. Specifically, pod and seed number and yield were significantly higher in 2016 than in 2017. Conversely, plant height, node number, and shoot dry weight were significantly higher in 2017 than in 2016. Based on the average values of the 2 years, pod and seed number in B × F − M was significantly higher than that in the other cultivars. Moreover, the yield of B × F − M and “Sachiyutaka” was significantly higher than that of B × F − E, B × F − L, and “Enrei.” Furthermore, 100-seed weight of “Sachiyutaka” was significantly higher than that of the other cultivars, except “Fukuyutaka.” Plant height and shoot dry weight of B × F − L tended to be higher than those of the other cultivars. The interaction between year and cultivar was detected for all test parameters, except seed number and yield. Therefore, multiple comparison analysis was performed among 12 cohorts for each test item, and the results are shown in Figure 2. Briefly, pod and seed number and yield were lower in all soybean cultivars in 2017 than in 2016. Furthermore, pod and seed number of B × F − E, B × F − M, “Enrei,” and “Sachiyutaka” decreased significantly. While the yield of “Sachiyutaka” decreased significantly, that of B × F − E, B × F − M, B × F − L, “Enrei,” and “Fukuyutaka” tended to decrease, albeit without significant differences. “Enrei,” “Sachiyutaka,” and “Fukuyutaka” are soybean cultivars that are suitable or possible to cultivate in the Chugoku region of Japan, including Shimane prefecture, where the cultivation test was conducted in the present study [51, 52]. Additionally, pod and seed numbers are the most important soybean yield components, which are primarily determined during the period from before and after flowering to pod set, including the beginning of the seed filling period [53]. However, increasing temperature during the growing season can negatively affect soybean leaf photosynthesis, growth, flowering, pod and seed number, and yield [54, 55]. In the present study, the monthly mean maximum temperature in August during the flowering period of soybean was 32.2°C in 2016 and 31.5°C in 2017 (Table 2). Specifically, in early August of 2017, when B × F − E and “Enrei” were flowering, the temperature remained above 35°C for 3 consecutive days. Furthermore, in late August of 2017, the temperature remained above 32°C for 4 consecutive days. Additionally, in October 2017, nearly 3.5 times the amount of precipitation in 2016 was recorded (Table 2). Soybean pod and seed number and yield in 2017 were significantly lower than the values in 2016 due to the effects of these meteorological factors (Table 4). Moreover, the 100-seed weight of B × F − M was lower than that of “Sachiyutaka” and “Fukuyutaka” (Table 4). Therefore, backcrossing with these cultivars is expected to produce soybean cultivars with larger seeds and higher yield.

YearCultivarPlant height (cm plant−1)Node number (No. plant−1)Shoot dry weight (g m−2)Pod number (No. m−2)seed number (No. m−2)100-seed weight (g)Yield (g m−2)
2016BxF–E50.311.1251.61426.7937.023.9214.4
BxF–M51.111.3298.51927.02276.822.9514.5
BxF–L71.112.1336.61036.01372.923.5325.8
Enrei34.39.5215.7542.6421.422.696.1
Sachiyutaka46.112.1300.31531.11742.933.8584.6
Fukuyutaka56.312.1267.11057.31377.329.8407.4
2017BxF–E67.413.4251.8318.8218.924.653.8
BxF–M69.413.8432.81180.71477.423.6348.2
BxF–L71.013.3424.1784.01037.720.7214.6
Enrei56.212.8340.0101.056.229.716.7
Sachiyutaka55.212.1344.2704.1974.429.3285.8
Fukuyutaka70.516.1467.9934.11245.625.0311.7
201651.511.4278.31253.41354.726.1357.1
201764.913.6376.8670.4835.025.5205.1
BxF–E58.8 bc12.2 a251.7 a872.7 b578.0 a24.2 a134.1 a
BxF–M60.3 bc12.5 ab365.7 b1553.8 c1877.1 c23.2 a431.4 c
BxF–L71.0 d12.7 ab380.4 b910.0 b1205.3 b22.1 a270.2 b
Enrei45.2 a11.1 a277.8 a321.8 a238.8 a26.1 a56.4 a
Sachiyutaka50.6 ab12.1 a322.3 ab1117.6 b1358.6 b31.6 b435.2 c
Fukuyutaka63.4 cd14.1 b367.5 b995.7 b1311.5 b27.4 ab359.6 bc
ANOVAYear (Y)***************ns***
Cultivar (C)*********************
Y x C*******ns**ns

Table 4.

Yield components of soybean cultivars in 2016 and 2017.

Values are presented as the means of three replicates. *p < 0.05, **p < 0.01, ***p < 0.001, and ns = not significant. Different letters indicate significant differences (Tukey’s HSD test) at p < 0.05 for different soybean cultivars.

Figure 2.

Yield components for each soybean cultivar in 2016 and 2017 growing seasons. Values are presented as the mean ± SE of three replicates. Different letters indicate significant differences (Tukey’s HSD test) at p < 0.05. (a) Plant height. (b) Node number. (c) Shoot dry weight. (d) Pod number. (e) Seed number. (f) 100-seed weight. (g) Yield.

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4. Occupancy of indigenous soybean-nodulating bradyrhizobia

4.1 Sampling of soybean root nodules and isolation of nodulating bradyrhizobia

The nodules used in the present experiment were collected from soybean roots at the flowering stage in 2017, as described in Section 3.2. The nodules were surface-sterilized with 70% ethanol for 3 min and diluted sodium hypochlorite solution (0.25% available chlorine) for 30 min, followed by washing with sterile distilled water. After washing, 24 nodules were randomly collected and transferred to 1.5 mL microcentrifuge tubes. Each nodule was homogenized in sterile distilled water and streaked onto a yeast extract–mannitol agar (YMA) plate [56]; to isolate a single colony per nodule, the plates were incubated for 5–7 days in the dark at 28°C. A total of 144 isolates were obtained from six soybean plants and used for PCR-restriction fragment length polymorphism (RFLP) analysis of the 16S–23S rRNA gene internal transcribed spacer (ITS) region.

4.2 PCR-RFLP analysis of the 16S: 23S rRNA gene ITS region

For DNA extraction, each isolate was cultured in 1.5 mL HM medium supplemented with 0.1% l-arabinose for 5–7 days in the dark at 28°C. Total DNA for use as the PCR template was extracted from the isolates in BL extraction buffer, as described previously [42] based on the method reported by Hiraishi et al. [57]. As reference strains, B. japonicum USDA 6T; B. diazoefficiens USDA 110T; and B. elkanii USDA 46, 76T, and 94 were used [16]. Total DNA of the reference strains for use as the PCR templates was also extracted using the same method [42, 57].

The 16S–23S rRNA gene ITS region was PCR-amplified using TaKaRa Ex Taq® Hot Start Version (TaKaRa Bio, Shiga, Japan) and the ITS primer set (BraITS-F: 5′-GACTGGGGTGAAGTCGTAAC-3′ and BraITS-R1: 5′-ACGTCCTTCATCGCCTC-3′) [58]. The PCR cycle comprised a pre-run at 94°C for 5 min, denaturation at 94°C for 30 s, annealing at 55°C for 30 s, and extension at 72°C for 1 min. This temperature control sequence was repeated for 30 cycles, followed by a final run at 72°C for 10 min. RFLP analysis of the 16S–23S rRNA gene ITS region was performed using the restriction enzyme MspI (TaKaRa Bio, Shiga, Japan). The PCR product was digested with the restriction enzyme at 37°C for 16 h, and the restricted fragments were separated using 3% agarose gel electrophoresis.

4.3 Occupancy of infected indigenous bradyrhizobia carrying hupSL genes

Eighty-seven indigenous soybean-nodulating bradyrhizobial isolates belonging to the cluster B. diazoefficiens USDA 110T were investigated for the presence of hupSL genes. PCR templates of the test isolates, obtained as described in Section 4.2, were used. The PCR amplification for hupSL was performed using KAPA Taq® Extra Hot Start ReadyMix with dye (Kapa Biosystems, USA) and the hupSL primer set (hupS-F261: 5′-TCGAACAGGCGTTGTAAGTG-3′, hupS-R830: 5′-TCGACTACGACGACACCATC-3′, hupL-F962:5′-TCGGGCAGATAGACCATTTC-3′ and hupL-R1632: 5′-GGGATCGAAGTGATCCTGAA-3′). The PCR cycle comprised a pre-run at 95°C for 3 min, denaturation at 95°C for 15 s, annealing at 55°C for 15 s, and extension at 72°C for 1 min. This temperature control sequence was repeated for 30 cycles, followed by a final run at 72°C for 1 min. The PCR products were electrophoresed on a 2% agarose gel to confirm amplification.

4.4 Occupancy of soybean-nodulating bradyrhizobia carrying hupSL genes

The occupancy rate of indigenous bradyrhizobia infecting each soybean cultivar is presented in Table 5. Based on the fragment patterns obtained from PCR–RFLP analysis, the indigenous isolates with the similar patterns as the five reference strains, namely B. japonicum USDA 6T; B. diazoefficiens USDA 110T; and B. elkanii USDA 46, 76T, and 94 were defined as Bj6, Bd110, Be46, Be76, and Be94, respectively. Since cluster Bd110 includes isolates carrying the hupSL genes, such as B. diazoefficiens USDA 110T and 122 [16], the occupancy rate of these isolates was also determined. PCR analysis targeting the hupSL genes revealed amplicons exhibiting zero to two bands. The isolates exhibiting two amplification products corresponding to hupS and hupL were defined as hupS+L+, those exhibiting a single amplification product corresponding to hupL were defined as hupSL+, and those exhibiting no amplification products were defined as hupSL. In B × F − E, Bd110 isolates exhibiting hupSL+ were the most dominant (62.5%), followed by Bd110 isolates exhibiting hupS+L+ (12.5%) and Bj6 isolates (12.5%). In B × F − M, Bj6 isolates were the most dominant (70.8%), followed by Bd110 isolates exhibiting hupSL+ (16.7%). In B × F − L, Bd110 isolates exhibiting hupSL+ (45.8%) were the most dominant, followed by Bd110 isolates exhibiting hupS+L+ (25.0%). In “Enrei,” Bj6 isolates were the most dominant (83.4%), followed by Bd110 isolates exhibiting hupSL+ (8.3%) or hupS+L+ (8.3%). In “Sachiyutaka,” Bd110 isolates exhibiting hupS+L+ (39.1%) were the most dominant, followed by Bd110 isolates exhibiting hupSL+ (34.8%). In “Fukuyutaka,” Bd110 isolates exhibiting hupS+L+ (37.5%) were the most dominant, followed by Bj6 (25.0%) isolates. “Sachiyutaka” and “Fukuyutaka” with the Rj4 genotype tended to present a higher occupancy rate of Bd110 isolates exhibiting hupS+L+. In contrast, soybean lines with the Rj2Rj3Rj4 genotype tended to present a lower occupancy rate of Bd110 isolates exhibiting hupS+L+. These results may be explained by the effect of the presence of Rj2. Rj2 restricts B. diazoefficiens USDA 122 [32]. Indigenous bradyrhizobial isolates, such as B. diazoefficiens USDA 110 T, which are not restricted by the Rj2 gene, can infect Rj gene-accumulated soybean lines. To solve this problem, the occupancy rate of inocula carrying the hupSL genes may be improved by inoculating Rj gene-accumulated soybean with B. diazoefficiens USDA 110T during cultivation. To test this hypothesis, we are currently investigating the effect of B. diazoefficiens USDA 110T inoculation on the growth and yield of various soybean genotypes, including Rj gene-accumulated ones.

CultivarBj6Bd110Be46Be76Be94
hupSLhupSL+hupS+L+
BxF–E12.58.362.512.50.00.04.2
BxF–M70.80.016.712.50.00.00.0
BxF–L0.08.345.825.04.216.70.0
Enrei83.40.08.38.30.00.00.0
Sachiyutaka13.08.734.839.10.04.40.0
Fukuyutaka25.020.816.737.50.00.00.0

Table 5.

Occupancy rate (%) of indigenous soybean-nodulating bradyrhizobia in each soybean cultivar in 2017.

Bj6, Bd110, Be46, Be76, and Be94 showed RFLP patterns similar to those of B. japonicum USDA 6T, B. diazoefficiens USDA 110T, B. elkanii USDA 46, B. elkanii USDA 76T, and B. elkanii USDA 94, respectively. hupSL, hupSL+, and hupS+L+ indicate isolates carrying or not carrying the hupS and/or hupL genes.

4.5 Correlation between the occupancy rate of indigenous bradyrhizobial strains and yield components of soybean

Correlation analysis was used to evaluate the association between the occupancy rate of indigenous bradyrhizobial strains and yield components. Correlation coefficients were computed based on data obtained from the measurement of yield components and occupancy rate of indigenous soybean-nodulating bradyrhizobia. The R package “psych” was used to compute and plot the correlations. Additionally, the significance of the correlations was tested using the “cor.test” function in R.

The results of correlation analysis between the occupancy rate of indigenous bradyrhizobial strains and yield components of soybean are presented in Figure 3. The correlation coefficients of the occupancy rate of Bj6 isolates with plant height, node number, shoot dry weight, pod number, seed number, 100-seed weight, and yield were − 0.30, −0.04, 0.09, −0.13, −0.15, 0.41, and − 0.16, respectively. The correlation coefficients of the occupancy rate of Bd110 isolates exhibiting hupSL with plant height, node number, shoot dry weight, pod number, seed number, 100-seed weight, and yield were 0.36, 0.68, 0.32, 0.25, 0.29, −0.18, and 0.33, respectively. The correlation coefficients of the occupancy rate of Bd110 isolates exhibiting hupSL+ with plant height, node number, shoot dry weight, pod number, seed number, 100-seed weight, and yield were 0.25, −0.26, −0.56, −0.18, −0.22, −0.41, and − 0.25, respectively. The correlation coefficients of the occupancy rate of Bd110 isolates exhibiting hupS+L+ with plant height, node number, shoot dry weight, pod number, seed number, 100-seed weight, and yield were − 0.02, 0.25, 0.40, 0.42, 0.51, 0.05, and 0.61, respectively. Among correlations between the occupancy rate of each indigenous bradyrhizobial strain and soybean yield, Bd110 isolates exhibiting hupS+L+ presented a strong positive correlation (r = 0.61), albeit without significant differences. Additionally, in another experiment, which revealed different results from the present findings, showed that the occupancy rate of B. diazoefficiens USDA 110T was correlated with the shoot dry weight of soybean (Figure 4). This result was obtained in the correlation analysis between the growth and the occupancy rate of B. diazoefficiens USDA 110T, B. japonicum USDA 6T and 123, and B. elkanii USDA 31 in soybean inoculated at the same bacterial density (106 cells mL−1) and cultivated for 5 weeks. Although this experiment was set in a greenhouse using cultivation pots, a significant positive correlation between the occupancy rate of USDA 110 and shoot dry weight of soybean plants was noted (r = 0.86, p = 0.03). A positive correlation between soybean growth and yield has been reported in previous study [59, 60, 61, 62]. In the present study, yield was positively correlated with plant height (r = 0.35) and shoot dry weight (r = 0.75), albeit without significant differences (Figure 3). Therefore, enhancing the infection rate of bradyrhizobial strains, such as B. diazoefficiens USDA 110T carrying the hupSL genes, may promote the growth of soybean and consequently increase yield.

Figure 3.

Correlation coefficient between the occupancy rate of Bd110 isolates carrying the hupSL gene and yield components. The correlation coefficients were computed based on data in Tables 4 and 5 (n = 6). A, B, C, D, E, F, G, H, I, J, and K indicate the occupancy rate (%) of Bj6, occupancy rate (%) of Bd110 exhibiting hupSL, occupancy rate (%) of Bd110 exhibiting hupSL+, occupancy rate (%) of Bd110 exhibiting hupS+L+, plant height, node number, shoot dry weight, pod number, seed number, 100-seed weight, and yield, respectively. *p < 0.01, **p < 0.001, respectively.

Figure 4.

Correlation between the occupancy rate of Bradyrhizobium diazoefficiens USDA 110T and shoot dry weight of soybean. The values were obtained based on the growth investigation of soybean inoculated with B. diazoefficiens USDA 110T, B. japonicum USDA 6T, B. japonicum USDA 123, and Bradyrhizobium elkanii USDA 31 at the same bacterial density (106 cells mL−1) and then cultivated for 5 weeks. Values are presented as the mean of three replicates.

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5. Conclusion

In the present chapter, we described the breeding and selection processes, shoot growth, yield components, and infection tendency of useful bradyrhizobial strains carrying the hupSL genes of Rj gene-accumulated soybean lines exhibiting the Rj2Rj3Rj4 genotype, obtained by crossing the Japanese soybean cultivars “Bonminori” (Rj2Rj3) and “Fukuyutaka” (Rj4).

First, we selected eight lines exhibiting the characteristics of the Rj2Rj2Rj4Rj4 genotype from 153 lines of F3 seeds following inoculation with B. japonicum Is−1 and B. japonicum Is−34 (Table 1). These eight lines were grown for several years, and three groups (B × F − E, B × F − M, and B × F − L) differing in terms of the flowering and ripening periods by approximately a week each were detected, which were cultivated further. Second, to investigate yield components, three Rj gene-accumulated soybean lines (B × F − E, B × F − M, and B × F − L) of F10 or F11 plant and three soybean cultivars (“Enrei,” “Sachiyutaka,” and “Fukuyutaka”) were cultivated in the 2016 and 2017 growing seasons. The yield of B × F − M was equivalent to that of “Sachiyutaka,” and this genotype likely possesses a greater yield potential than the parent soybean cultivar “Fukuyutaka,” among the Rj gene-accumulated soybean lines. However, the 100-seed weight of B × F − M was lower than that of “Sachiyutaka” and “Fukuyutaka.” Therefore, backcrossing with these cultivars is expected to produce soybean cultivars with larger seeds and higher yield potential. Third, to assess the occupancy rate of infected indigenous soybean-nodulating bradyrhizobia carrying the hupSL genes, we collected nodules from soybean roots and performed PCR-RFLP analysis of the 16S–23S rRNA gene ITS region. Furthermore, 87 indigenous soybean-nodulating bradyrhizobial strains belonging to the B. diazoefficiens USDA 110T cluster were investigated for the presence of the hupSL genes using PCR. The occupancy rate of Bd110 isolates carrying the hupSL genes tended to be lower in the Rj gene-accumulated soybean lines than in “Sachiyutaka” and “Fukuyutaka.” In addition, among the Rj gene-accumulated soybean lines, B × F − L presented the highest occupancy rate of Bd110 isolates carrying the hupSL genes. Based on these results, during the cultivation of Rj gene-accumulated soybean, the occupancy rate of inocula carrying the hupSL genes can be improved by inoculating B. diazoefficiens USDA 110T, which is not restricted by the Rj2 gene.

Finally, to evaluate the association between the occupancy rate of indigenous bradyrhizobial strains and yield components of soybean, correlation analysis was performed. Correlation coefficients of the occupancy rate of Bd110 isolates exhibiting hupS+L+ with plant height, node number, shoot dry weight, pod number, seed number, 100-seed weight, and yield were − 0.02, 0.25, 0.40, 0.42, 0.51, 0.05, and 0.61, respectively, and the occupancy rate of Bd110 isolates exhibiting hupS+L+ was strongly and positively correlated with yield components (r = 0.61), albeit without significant differences. Furthermore, soybean yield was positively correlated with plant height (r = 0.35) and shoot dry weight (r = 0.75), albeit without significant differences. Therefore, enhancing the infection rate of bradyrhizobial strains, such as B. diazoefficiens USDA 110T carrying the hupSL genes, may promote the growth of soybean and consequently increase its yield. In the future, we intend to conduct further inoculation tests with useful strains, such as B. diazoefficiens USDA 110T carrying the hupSL genes, to evaluate in greater detail the availability of Rj gene-accumulated soybean lines with the Rj2Rj3Rj4 genotype for improving productivity.

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Acknowledgments

The authors thank the members of the laboratories of Shimane University and University of Miyazaki involved in the present study. Additionally, the authors thank the technical staff of the Agricultural Science Section, Education and Research Center for Biological Resources, Faculty of Life and Environmental Science, Shimane University for their support in managing soybean cultivation. The authors also thank the Faculty of Life and Environmental Sciences at Shimane University for financial support to publish this chapter.

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Conflict of interest

The authors declare no conflict of interest.

References

  1. 1. Ministry of Agriculture, Forestry, and Fisheries of Japan (MAFF). The circumstances on soybean (in Japanese) [Internet]. 2021. Available from: https://www.maff.go.jp/j/seisan/ryutu/daizu/attach/pdf/index-144.pdf [Accessed: November 29, 2021]
  2. 2. Jordan DC. Transfer of Rhizobium japonicum Buchanan 1980 to Bradyrhizobium gen. Nov., a genus of slow-growing, root nodule bacteria from leguminous plants. International Journal of Systematic Microbiology. 1982;32:136-139. DOI: 10.1099/00207713-32-1-136
  3. 3. Scholla MH, Elkan GH. Rhizobium fredii sp. nov. a fast-growing species that effectively nodulates soybeans. International Journal of Systematic Bacteriology. 1984;34:484-486. DOI: 10.1099/0207713-34-4-484
  4. 4. Chen WX, Yan GH, Li JL. Numerical taxonomic study of fast-growing soybean rhizobia and a proposal that Rhizobium fredii be assigned to Sinorhizobium gen. nov. International Journal of Systematic Microbiology. 1988;38:392-397. DOI: 10.1099/00207713-38-4-392
  5. 5. Kuykendall LD, Saxena B, Cevine TE, Udell SE. Genetic diversity in Bradyrhizobium Jordan 1982 and a proposal for Bradyrhizobium elkanii sp. nov.. Canadian journal. Microbiology. 1992;38:501-505. DOI: 10.1139/m92-082
  6. 6. Young JM. The genus name Ensifer Casida 1982 takes priority over Sinorhizobium Chen et al. 1988, and Sinorhizobium morelense Wang et al. 2002 is a later synonym of Ensifer adhaerens Casida 1982. Is the combination ‘Sinorhizobium adhaerens’ (Casida 1982) Willems et al. 2003 legitimate? Request for an opinion. International Journal of Systematic and Evolutionary Microbiology. 2003;53:2107-2110. DOI: 10.1099/ijs.0.02665-0
  7. 7. Delamuta JRM, Riberio RA, Ormeño-Orrillo E, Melo IS, Maritínez-Romero E, Hungria M. Polyphasic evidence supporting the reclassification of Bradyrhizobium japonicum group Ia strains as Bradyrhizobium diazoefficiens sp. nov. International Journal of Systematic and Evolutionary Microbiology. 2013;63:3342-3351. DOI: 10.1099/ijs.0.049130-0
  8. 8. Chen W, Wang E, Wang S, Li Y, Chen X, Li Y. Characteristics of Rhizobium tianshanense sp. nov., a moderately and slowly growing root nodule bacterium isolated from an arid saline environment in Xinjiang, People’s republic of China. International Journal of Systematic Bacteriology. 1995;45:153-159. DOI: 10.1099/00207713-45-1-153
  9. 9. Xu LM, Ge C, Cui Z, Li J, Fan H. Bradyhizobium liaoningense sp. nov., isolated from the root nodules of soybeans. International Journal of Systematic Bacteriology. 1995;45:706-711. DOI: 10.1099/00207713-45-4-706
  10. 10. Tan ZY, Xu XD, Wang ET, Gao JL, Martinez-Romero E, Chen WX. Phylogenetic and genetic relationships of Mesorhizobium tianshanense and related rhizobia. International Journal of Systematic Bacteriology. 1997;47:874-879. DOI: 10.1099/00207713-47-3-874
  11. 11. Peng GX, Tan ZY, Wang ET, Reinhold-Hurek B, Chen WF, Chen WX. Identification of isolates from soybean nodules in Xinjiang region as Sinorhizobium xinjiangense and genetic differentiation of S. xinjiangense from Sinorhizobium fredii. International Journal of Systematic and Evolutionary Microbiology. 2002;52:457-462. DOI: 10.1099/00207713-52-2-457
  12. 12. Yao ZY, Kan FL, Wang ET, Wei GH, Chen WX. Characterization of rhizobia that nodulate legume species of the genus Lespedeza and description of Bradyrhizobium yuanmingense sp. nov. International Journal of Systematic and Evolutionary Microbiology. 2002;52:2219-2230. DOI: 10.1099/ijs.0.01408-0
  13. 13. Vinuesa P, Rojas-Jiménez K, Contreras-Moreira B, Mahna SK, Prasad BN, Moe H, et al. Multilocus sequence analysis for assessment of the biogeography and evolutionary genetics of four Bradyrhizobium species that nodulate soybeans on the Asiatic continent. Applied and Environmental Microbiology. 2008;74:6987-6996. DOI: 10.1128/AEM.00875-08
  14. 14. Adhikari D, Kaneto M, Itoh K, Suyama K, Pokharel BB, Gaihre YK. Genetic diversity of soybean-nodulating rhizobia in Nepal in relation to climate and soil properties. Plant and Soil. 2012;357:131-145. DOI: 10.1007/s11104-012-1134-6
  15. 15. Evans HJ, Harker AR, Papen H, Russell SA, Hanus FJ, Zuber M. Physiology, biochemistry, and genetics of the uptake hydrogenase in rhizobia. Annual Review of Microbiology. 1987;41:335-361. DOI: 10.1146/annurev.mi.41.100187.002003
  16. 16. Saeki Y, Aimi N, Hashimoto M, Tsukamoto S, Kaneko A, Yoshida N, et al. Grouping of Bradyrhizobium USDA strains by sequence analysis of 16S rDNA and 16S-23S rDNA internal transcribed spacer region. Soil Science and Plant Nutrition. 2004;50:517-525. DOI: 10.1080/00380768.2004.10408508
  17. 17. Masuda S, Saito M, Sugawara C, Itakura M, Eda S, Minamisawa K. Identification of the hydrogen uptake gene cluster for chemolithoautotrophic growth and symbiosis hydrogen uptake in Bradyrhizobium diazoefficiens. Mirobes and Environments. 2016;36:76-78. DOI: 10.1264/jsme2.ME15182
  18. 18. Drevon J, Kalia VC, Heckmann M, Salsac I. Influence of the Bradyrhizobium hydrogenase on the growth of Glycine and Vigna species. Applied and Environmental Microbiology. 1987;53:610-612. DOI: 10.1128/aem.53.3.610-612.1987
  19. 19. Williams LF, Lynch DL. Inheritance of a non-nodulating character in the soybean. Agronomy Journal. 1954;46:28-29. DOI: 10.2134/agronj1954.00021962004600010008x
  20. 20. Caldwell BE. Inheritance of a strain-specific ineffective nodulation in soybean. Crop Science. 1966;6:427-428. DOI: 10.2135/cropsci1966.0011183X000600050010x
  21. 21. Vest G. Rj3 - A gene conditioning ineffective nodulation in soybean. Crop Science. 1970;10:34-35. DOI: 10.2135/cropsci1970.0011183X001000010013x
  22. 22. Vest G, Caldwell BE. Rj4 - A gene conditioning ineffective nodulation in soybean. Crop Science. 1972;12:692-693. DOI: 10.2135/CROPSCI1970.0011183X001000010013X
  23. 23. Weiser GV, Skipper HD, Wollum AG. Exclusion of inefficient Bradyrhizobium japonicum serogroups by soybean genotypes. Plant and Soil. 1990;121:99-105. DOI: 10.1007/BF00013102
  24. 24. Trese AT. A single dominant gene in McCall soybean prevents effective nodulation with Rhizobium fredii USDA257. Euphytica. 1995;81:279-282. DOI: 10.1007/BF00025618
  25. 25. Madsen EB, Madsen LH, Radutoiu S, Olbryt M, Rakwalska M, Szczyglowski K, et al. A receptor kinase gene of the LysM type is involved in legume perception of rhizobial signals. Nature. 2003;425:637-640. DOI: 10.1038/nature02045
  26. 26. Arrighi JF, Barre A, Amor BB, Bersoult A, Soriano LC, Mirabella R, et al. The Medicago truncatula lysine motif-receptor-like kinase gene family includes NFP and new nodule-expressed genes. Plant Physiology. 2006;142:265-279. DOI: 10.1104/pp.106.084657
  27. 27. Indrasumunar A, Gresshoff PM. Duplicated nod-factor receptor 5 (NFR5) genes are mutated in soybean (Glycine max L. Merr.). Plant Signaling and Behavior. 2010;5:535-536. DOI: 10.4161/psb.11028
  28. 28. Nishimura R, Hayashi M, Wu GJ, Kouchi H, Imaizumi-Anraku H, Murakami Y, et al. HAR1 mediates systemic regulation of symbiotic organ development. Nature. 2002;420:426-429. DOI: 10.1038/nature01231
  29. 29. Krusell L, Madsen LH, Sato S, Aubert G, Genua A, Szczyglowski K, et al. Shoot control of root development and nodulation is mediated by a receptor kinase. Nature. 2002;420:422-426. DOI: 10.1038/nature01207
  30. 30. Searle IR, Men AE, Laniya TS, Buzas DM, Iturbe-Ormaetxe I, Carroll BJ, et al. Long-distance signaling in nodulation directed by a CLAVATA1-like receptor kinase. Science. 2003;299:109-112. DOI: 10.1126/science.1077937
  31. 31. Schnabel E, Journet EP, de Carvalho-Niebel F, Duc G, Frugoli J. The Medicago truncatula SUNN gene encodes a CLV1-like leucine-rich repeat receptor kinase that regulates nodule number and root length. Plant Molecular Biology. 2005;58:809-822. DOI: 10.1007/s11103-005-8102-y
  32. 32. Ishizuka J, Suemasu Y, Mizogami K. Preference of Rj-soybean cultivars for Bradyrhizobium japonicum for nodulation. Soil Science and Plant Nutrition. 1991;37:15-21. DOI: 10.1080/00380768.1991.10415005
  33. 33. Hayashi M, Saeki Y, Haga M, Harada K, Kouchi H, Umehara Y. Rj (rj) genes involved in nitrogen-fixing root nodule formation in soybean. Breeding Science. 2012;61:544-553. DOI: 10.1270/jsbbs.61.544
  34. 34. Yang S, Tang F, Gao M, Krishnan HB, Zhu H. R gene-controlled host specificity in the legume-rhizobia symbiosis. Proceeding of the National Academy of Sciences of the United States of America. 2010;107:18735-18740. DOI: 10.1073/pnas.1011957107
  35. 35. Sugawara M, Umehara Y, Kaga A, Hayashi M, Ishimoto M, Sato S, et al. Symbiotic incompatibility between soybean and Bradyrhizobium arises from one amino acid determinant in soybean Rj2 protein. PLoS One. 2019;14:e0222469. DOI: 10.1371/journal.pone.0222469
  36. 36. van Loon LC, Rep M, Pieterse CMJ. Significance of inducible defense-related proteins in infected plants. Annual Review of Phytopathology. 2006;44:135-162. DOI: 10.1146/annurev.phyto.44.070505.143425
  37. 37. Hayashi M, Shiro S, Kanamori H, Mori-Hosokawa S, Sasaki-Yamagata H, Sayama T, et al. A thaumatin-like protein, Rj4, controls nodule symbiotic specificity in soybean. Plant and Cell Physiology. 2004;55:1679-1689. DOI: 10.1093/pcp/pcu099
  38. 38. Okazaki S, Zehner S, Hempel J, Lang K, Göttfert M. Genetic organization and functional analysis of the type III secretion system of Bradyrhizobium elkanii. FEMS Microbiology Letters. 2009;295:88-95. DOI: 10.1111/j.1574-6968.2009.01593.x
  39. 39. Tsurumaru H, Hashimoto S, Okizaki K, Kanesaki Y, Yoshikawa H, Yamakawa T. A putative type III secretion system effector encoded by the MA20_12780 gene in Bradyrhizobium japonicum Is−34 causes incompatibility with Rj4 genotype soybeans. Applied and Environmental Microbiology. 2015;81:5812-5819. DOI: 10.1128/AEM.00823-15
  40. 40. Ishizuka J, Kim SD, Hussain AKMA, Yamakawa T. Soybean preference for Bradyrhizobium japonicum for modulation. Isolation of Rj2Rj4-lines from the cross of soybean cvs. IAC-2 (Rj2) and Hill (Rj4). Soil Science and Plant Nutrition. 1993;39:79-86. DOI: 10.1080/00380768.1993.10416977
  41. 41. Yamakawa T, Eriguchi M, Hussain AKMA, Ishizuka J. Soybean preference for Bradyrhizobium japonicum for nodulation. Nodulation by Rj2Rj3Rj4-genotypes isolated from the progenies of cross of soybean cvs. IAC-2 (Rj2Rj3) and Hill (Rj4). Soil Science and Plant Nutrition. 1999;45:461-469. DOI: 10.1080/00380768.1999.10409360
  42. 42. Minami M, Yamakawa T, Yamamoto A, Akao S, Saeki Y. Estimation of nodulation tendency among Rj-genotype soybeans using the bradyrhizobial community isolated from an andosol. Soil Science and Plant Nutrition. 2009;55:65-72. DOI: 10.1111/j.1747-0765.2008.00333.x
  43. 43. Shiro S, Yamamoto A, Umehara Y, Hayashi M, Yoshida N, Nishiwaki A, et al. Effect of Rj genotype and cultivation temperature on the community structure of soybean-nodulating bradyrhizobia. Applied and Environmental Microbiology. 2012;78:1243-1250. DOI: 10.1128/AEM.06239-11
  44. 44. Ministry of Agriculture, Forestry, and Fisheries of Japan (MAFF). The development and diffusion of new soybean cultivars (in Japanese) [Internet]. 2015. Available from: https://www.maff.go.jp/j/seisan/ryutu/daizu/d_ziten/pdf/fukyu.pdf [Accessed: December 1, 2021]
  45. 45. Togashi A, Oikawa S. Leaf productivity and persistence have been improved during soybean (Glycine max) domestication and evolution. Journal of Plant Research. 2021;134:223-233. DOI: 10.1007/s10265-021-01263-x
  46. 46. Cole MA, Elkan GH. Transmissible resistance to penicillin G, neomycin and chloramphenicol in Rhizobium japonicum. Antimicrobial Agents and Chemotherapy. 1973;4:248-253. DOI: 10.1128/aac.4.3.248
  47. 47. Sameshima R, Iwasa T, Sadowsky J, Hamada T, Kasai H, Shutsrirung A, et al. Phylogeny and distribution of extra-slow-growing Bradyrhizobium japonicum harboring high copy numbers of RSα, RSβ and IS1631. FEMS Microbiology Ecology. 2003;44:191-202. DOI: 10.1016/S0168-6496(03)00009-6
  48. 48. Saeki S, Akagi I, Takaki H, Nagatomo Y. Diversity of indigenous Bradyrhizobium strains isolated from three different Rj-soybean cultivars in terms of randomly amplified polymorphic DNA and intrinsic antibiotic resistance. Soil Science and Plant Nutrition. 2000;46:917-926. DOI: 10.1080/00380768.2000.10409157
  49. 49. R Core Team R. Available from. In: A Language and Environment for Statistical Computing. Vienna, Austria: R Foundation for Statistical Computing; 2020 https://www.R-project.org/ [Accessed: December 23, 2021]
  50. 50. Iseki R. The page of Iseki Ryuta. ANOVAKUN/Release Notes (in Japanese) [Internet]. 2020. Available from: http://riseki.php.xdomain.jp/index.php?ANOVA%E5%90%9B%2F%E3%83%AA%E3%83%AA%E3%83%BC%E3%82%B9%E3%83%8E%E3%83%BC%E3%83%88 [Accessed: December 23, 2021]
  51. 51. Ministry of Agriculture, Forestry, and Fisheries of Japan (MAFF). The characteristics of Japanese soybean cultivars (in Japanese) [Internet]. 2019. Available from: https://www.maff.go.jp/j/seisan/ryutu/daizu/d_ziten/attach/pdf/index-21.pdf [Accessed: January 24, 2022]
  52. 52. Konno T, Takahashi T, Nakano K, Nira R, Ohashi Y, Kudo T, et al. Survey of wet and dry stress in soybean in Japanese farmers’ fields using dry and wet indices based on FAO56 model (in Japanese). Japanese Journal of Crop Science. 2020;89:337-345. DOI: 10.1626/jcs.89.337
  53. 53. Kantolic A, Slafer GA. Reproductive development and yield components in indeterminate soybean as affected by post-flowering photoperiod. Field Crops Research. 2005;93:212-222. DOI: 10.1016/j.fcr.2004.10.001
  54. 54. Kumagai E, Sameshima R. Genotypic differences in soybean yield responses to increasing temperature in a cool climate are related to maturity group. Agricultural and Forest Meteorology. 2014;198-199:265-272. DOI: 10.1016/j.agrformet.2014.08.016
  55. 55. Shiro S, Mazuka S, Kadowaki M, Saeki Y. The effect of cultivation temperature on the soybean (Glycine max) growth and community structure of bradyrhizobia (in Japanese). Japanese Journal of Soil Science and Plant Nutrition. 2021;92:255-262. DOI: 10.20710/dojo.92.3_255
  56. 56. Vincent JM. A Manual for the Practical Study of the Root-Nodule Bacteria. International Biological Program Handbook No. 15. Oxford: Blackwell Scientific Publishers; 1970. p. 164. DOI: 10.1002/jobm.19720120524
  57. 57. Hiraishi A, Kamagata Y, Nakamura K. Polymerase chain reaction amplification and restriction fragment length polymorphism analysis of 16S rRNA genes from methanogens. Journal of Fermentation and Bioengineering. 1995;79:523-529. DOI: 10.1016/0922-338X(95)94742-A
  58. 58. Saeki Y, Aimi N, Tsukamoto S, Yamakawa T, Nagatomo Y, Akao S. Diversity and geographical distribution of indigenous soybean-nodulating bradyrhizobia in Japan. Soil Science and Plant Nutrition. 2006;52:418-426. DOI: 10.1111/j.1747-0765.2006.00050.x
  59. 59. Shirakawa T, Ueno N, Shimada S, Horie T. Correlation between yielding ability and dry matter productivity during initial seed filling stage in various soybean genotypes. Plant Production Science. 2004;7:138-142. DOI: 10.1626/ pps.7.138
  60. 60. Kakiuchi J, Kobata T. The relationship between dry matter increase of seed and shoot during the seed-filling period in three kinds of soybeans with different growth habits subjected to shading and thinning. Plant Production Science. 2006;9:20-26. DOI: 10.1626/pps.9.20
  61. 61. Kasu-Bandi BT, Kidinda LK, Kasendue GN, Longanza LB, Emery KL, Lubobo AK. Correlations between growth and yield parameters of soybean (Glycine max (L.) Merr.) under the influence of Bradyrhizobium japonicum in Kipushi (the Democratic Republic of Congo). American Journal of Agricultural and Biological Sciences. 2019;14:86-94. DOI: 10.3844/ajabssp.2019.86.94
  62. 62. Borowska M, Prusinski J. Effect of soybean cultivars sowing dates on seed yield and its correlation with yield parameters. Plant, Soil and Environment. 2021;67:360-366. DOI: 10.17221/73/2021-PSE

Written By

Sokichi Shiro and Yuichi Saeki

Submitted: 03 January 2022 Reviewed: 24 January 2022 Published: 22 March 2022