Junji Ishizuka

Preference of Rj-soybean cultivars for Bradyrhizobium japonicum for nodulation

Abstract In order to Investigate the correlation between the preference of soybeans (Glycine max L.) for Bradyrhizobium japonicum for nodulation and their Rj-genotypes, rhizobia were isolated from eight cultivars (non-Rj-cultivars: T202, Tol-1, and CNS-J; Rj 2 Rj 3-ones: Hardee, IAC-2, and Bonminori; Rj 4-ones: Hill and Amsoy 71) grown in the field and their compatibilities with Hill and IAC-2 were examined. Sixty-three percent of the nodules of the Rj 2 Rj 3-cultivars were occupied by rhizobia of nodulation-type C, which were compatible with the Rj 2 Rj 3-cultivars but incompatible with the Rj 4-one. Sixty-one percent of the nodules of the Rj 4 cultivars were occupied by isolates of nodulation-type B, which were compatible with the Rj{ni4}-cultivars but incompatible with the Rj 2 Rj 3-one. Non -Rj- cultivars preferred rhizobia of nodulation-type A, which were compatible with both Rj-cultivars. To estimate the effect of planting of Rj-cultivars on the rhizobial population in soils, Rj 2 Rj 3-(IAC-2) and R...

Trends in biological nitrogen fixation research and application

In the world each year 17.2×107 tons of N are biologically fixed. Biological nitrogen fixation (BNF) contributes to plant production in arable lands and in natural ecosystems. Research to improve BNF is progressing through the breeding of efficient N-fixing organisms and host plants, selection of the best combinations of host plant and microsymbiont, and by the improvement of inoculation techniques and field management. Biotechnology is useful for the creation of promising N2-fixing organisms. However, to increase plant production through enhanced BNF the constraints in establishing effective N2-fixing systems in the field should be understood and eliminated.

Organic acid metabolism and root excretion of malate in wheat cultivars under aluminium stress.

The effects of aluminium (Al) on the metabolism of organic acids synthesised via nonphotosynthetic carbon fixation in the roots and on malate exudation were investigated in Al-tolerant Shirosanjyaku (SH) and Al-sensitive Chikushikomugi (CK) wheat cultivars labelled with bicarbonate-(14)C. Aluminum triggered the excretion of (14)C into the solution, especially in the SH that excreted 2.5 times more (14)C than the CK. The loss of radioactivity (about 10%) into the solution represented a small drain in the (14)C reserve found in the roots. In the organic acid fraction within the roots, malate contained the greatest amount of (14)C, and this amount decreased rapidly with time in both cultivars. The disappearance of radioactivity in the malate resulted from metabolism and translocation rather than to root efflux. Aluminium decreased the malate concentrations in roots of both cultivars. The Al-sensitive cultivar had higher concentrations of malate regardless of the presence of Al. It was therefore assumed that the decrease of malate concentration in roots under Al stress did not result from the decline in malate synthesis but due to an increase in malate decomposition. This response was interpreted as the result of the Al-induced stress and not as the cause of a differential Al-tolerance between the wheat cultivars. An important component of the differential Al tolerance between SH and CK is the greater ability of the Al-tolerant cultivar to excrete malate from the roots, which is independent of its internal concentration in the roots.

Soybean preference for Bradyrhizobium japonicum for nodulation : Nodulation by Rj2Rj3Rj4-Genotypes isolated from the progenies of a cross between soybean cvs. IAC-2 (Rj2Rj3) and hill (Rj4)

Abstract For the increase of the occupation ratio of inoculum strain in the competition with indigenous rhizobia, the relationship between Rj-genotypes of soybean and the preference of Rj-cultivars for various types of rhizobia for nodulation was investigated by using the Rj 2 Rj 4-genotype of soybean isolated from the cross between the Rj 2 Rj 3-cultivar IAC-2 and Rj 4-one Hill (Ishizuka et al. 1993: Soil Sci. Plant Nutr., 39, 79-86). Firstly, these Rj 2 Rj 4-genotypes were found to harbor the Rj 3-gene. The Rj 2Rj3Rj4-genotypes of soybean were considered to exhibit a more narrow microsymbiont range for nodulation than the Rj 2 Rj 3-and Rj4-cultivars. Therefore, rhizobia were isolated from the nodules of various Rj-genotypes of soybeans grown in soils, and the preference of the Rj 2 Rj 3 Rj 4-genotype for indigenous rhizobia was examined. The nodule occupancy of serotype 110 was significantly higher in the bacteroids of the nodules from the Rj 2 Rj 3 Rj 4-rgenotypes than in those from the other genotypes...

Effects of nitrate application on growth, modulation, and nitrogen fixation of nitrate-tolerant mutants of soybean

Abstract Nitrate-tolerant mutants of soybean (Glycine max L. Merr.) cv. Bragg, nts1116 and nts1007, were cultured hydroponically to study the effects of nitrate on plant growth, nodulation, and nitrogen fixation compared to the parent cultivar Bragg. The vegetative growth of nts1116 was the most active. Absorption rate of nitrate increased with the duration of the treatment. The absorption rate was slightly higher in nts1116 compared to ntsl007 and Bragg. Nitrogen accumulation of the nitrate-treated plants through biological nitrogen fixation was larger in the order of ntsl007, nts1116, and Bragg. However, N accumulation from nitrate did not differ among the 3 lines. Nitrate reductase activities in the nodules were the highest in Bragg followed by nts1116 and nts1007, regardless of the nitrate treatment and assay time, and were negatively correlated with the nodule masses. Ureide concentration was the highest in nts1007 followed by nts1116 and Bragg, and was positively correlated with the nodule masses an...

Relationship between serotypes of Bradyrhizobium japonicum and their compatibility with Rj-cultivars for nodulation

Abstract In order to investigate the preference of Rj-cultivars of soybean for Bradyrhizobium japonicum, rhizobia isolated from field-grown soybeans were classified into nodulation-types A, B, and C based on the compatibility with Rj-cultivars, and relationship between nodulation-types and serotypes of rhizobia was examined by agglutination reactions of B. japonicum isolated from the nodules of the Rj 2 Rj 3-soybean cultivars with the antisera against somatic antigens of B. japonicum. Twelve antigens of nodulation-type C isolates (compatible with the Rj 2 Rj 3-cultivar, but incompatible with the Rj 4-cultivar) and strain USDA-61 were agglutinated with one or two antisera against the nodulation-type C strains, but did not react with antisera against the nodulation-type A strains (compatible with the Rj 2 Rj 3- and Rj 4-cultivars). On the other hand, 3 out of 10 antigens of type A isolates reacted only with antisera against type C strains, and 2 of them reacted with both antisera against type A and C strain...

Characteristics of molybdenum absorption and translocation in soybean plants

Abstract Investigations on the absorption and translocation of molybdenum (Mo) in soybean plants (Glycine max) grown in the field were conducted, and the following results were obtained. Up to the flower-bud-appearing stage, little absorption of Mo was detected. The Mo accumulation in the nodules may thus be highly dependent on the Mo contained in the seeds during the early growing period, and it can be said that the Mo contained in the seeds may play an important role in the early plant growth and probably in the nitrogen fixation by nodules. After the middle of June, the soybean plants began to absorb soii-Mo, and the Mo concentrations. in all the plant parts increased, especially in the nodules. During the podfilling stage, the Mo concentrations in the roots and pod shells decreased rapidly, whiie, in contrast, that in the seeds Increased. The Mo concentrations in the nodules, stems and leaves did not decrease so much, probably indicating negligible translocation to the seeds from these organs. Soybean...

Nodulation of Rj-soybean varieties with Rhizobium fredii USDA 193 under limited supply of nutrients

Abstract The compatibility between rhizobia and host plants for nodulation was determined based on the genetic and physiological properties of both symbionts. It has been observed that soybean varieties carrying the Rj-gene were not nodulated effectively by certain strains or groups of rhizobia. Soybeans carrying the Rj 2-gene, Rj 2-varieties, were found to nodule ineffectively by the rhizobial strains belonging to the 3-24-44 and 122 serogroups (Caldwell 1966). In the same way, Rj 3- and Rj 4-varieties were found to nodule ineffectively by strains USDA 33 (Vest 1970) and USDA 61 (Vest and Caldwell 1972), respectively.

Soybean preference for Bradyrhizobium japonicum for nodulation: Occupation of serogroup USDA110 in nodules of soybean plants harboring various Rj-genes grown in a field

Abstract For examining the probability of increase in the occupation ratio of inoculated rhizobium in nodules, various Rj-soybean cultivars including the Rj 2 Rj 3 Rj 4-lines of soybean were grown in a field of the Kyushu University Farm. Bradyrhizobium japonicum USDA110 that carries uptake hydrogenase (Hup+) was used as an inoculum. The relative efficiency of nitrogen fixation generally increased by the inoculation. However, there were no significant differences in the effects among the genotypes of the host plants. The occupation ratio of serogroup USDA110 in the nodules on the taproot of the inoculated plants was in the range of 77–100%, suggesting that the B. japonicum strain USDA110 infected taproots immediately after inoculation. The occupation ratios in the nodules on the lateral roots were 53–67, 40–86, 63–83, and 62–77% in inoculated plants of the non-Rj-, Rj 2 Rj 3-, Rj 4-, and Rj 2 Rj 3 Rj 4-genotypes, respectively, and they decreased in all the genotypes with the progression of growth. At the time of the first sampling, the occupation ratios on the lateral roots of these Rj 2 Rj 3 Rj 4-genotypes showed values intermediate between those of IAC-2 (Rj 2 Rj 3) and Hill (Rj 4) , which were the parent cultivars of the Rj 2 Rj 3 Rj 4-lines, B340, B349, and C242. The reduction in the occupation ratio of the serogroup USDA110 for about 1 month after the first sampling was the lowest (0.13–0.16) in the Rj 2 Rj 3 Rj 4-genotypes, excluding B349, followed by the non-Rj- and Rj 2 Rj 3-genotypes and highest (0.52–0.69) in the Rj 4-genotypes, excluding Hill. Therefore, it was considered that the population of compatible rhizobia with host soybean plants increased in the rhizosphere with the progression of the development and growth. The results showed that with the expansion of the root area of host plants, the occupation ratio of type A rhizobia including the serogroup USDA110 was high. Therefore, the Rj 2 Rj 3 Rj 4-genotypes were superior to other Rj-genotypes in terms of the inoculation effects of nodulation type A rhizobium, B. japonicum USDA110. However, the preference of the Rj 2 Rj 3 Rj 4-genotype for serogroup USDA110 is not sufficient to rule out the competition with the other serogroups in this study. Therefore, the study should be centered on the isolation of more efficient (Hup+) and highly compatible rhizobial strains with the Rj 2 Rj 3 Rj 4- genotypes.

Natural 15N Abundance of Field Grown Soybean Grains Harvested in Various Locations in Japan and Estimate of the Fractional Contribution of Nitrogen Fixation

Natural 15N concentrations (δ15N values by per mil relative to atmospheric nitrogen) of soybean grains and soils from various locations in Japan were analyzed by a ratio mass spectrometer. The δ15N values of nonnodulating plants showed considerable variations ranging from -3.34 to 11.56‰. The δ15N values of the nodulated plants also differed depending on the location. but mostly they were lower than the values of the nonnodulating plants in each location. The %N derived from atmospheric N2 in the nodulated plants based on the differences in the δ15N values was estimated at 50% as an average of 37 measurements. The δ15N values of the soils where soy beans were grown, showed small variations compared to those of soy bean grains. There was no special relation between the δ15N values of the soils and soybean grains.