• KOREAN JOURNAL OF CROP SCIENCE
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• v.37 no.1
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• pp.16-21
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• 1992

Increase in nodulation and nitrogen fixation was achieved partly through the isolation of supernodulating soybean mutant plants. This experiment was conducted to compare nodulation, nitrogen fixation, and early growth characters of wild type 'Bragg' with those of its supernodulating soybean mutant, 'nts 382' and 'nts 246'. At 31 days after planting, nodule dry weight of nts mutants was 2.5 to 3.7 times greater than that of Bragg. Higher nodulation of nts mutants showed the reduced top growth, indicating that photosynthates might be translocated and used for nodule growth attached to the root system. Total acetylene reduction activity was higher in nts mutants than Bragg, whereas specific acetylene reduction activity of nts mutant was the half of that of Bragg. Mixture of nts mutants and Bragg did not affect nodulation characters each other, suggesting that factors affecting supernodulating characters exist inside rather than outside the root system.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.43 no.1
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• pp.28-31
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• 1998

Nodule development was regulated partially by host plant factors originating in the shoots and roots. This study was performed to identify the origin of the factors regulating nodulation in supernodulating soybean (Glycine max [L.] Merr.) mutant 'SS2-2' which was isolated recently from ethyl methanesulfonate (EMS) mutagenesis of 'Sinpaldalkong 2'. Self- and reciprocal-grafts were made among three soybean genotypes which consisted of two supernodulating mutants, SS2-2 and 'nts 382', and a normal nodulating Sinpaldalkong 2. Self-grafted supernodulating mutants were characterized by greater nodule number, nodule dry weight, and $C_2$H$_2$ reduction activity than self-grafted wild types. They were also characterized by relatively higher nodule to root dry weight. Significant shoot genotypic effects were observed on nodule number, nodule dry weight, and $C_2\;H_2$ reduction activity per plant, whereas varying root genotypes had no effects. From this result, it is surmised that supernodulating characters are controlled by a graft-transmissible shoot factor, and mutant SS2-2 may have similar nodulation mechanism to the former supernodulating nts 382. In all grafts, both supernodulating mutants and Sinpaldalkong 2 maintained the similar balance between above ground and below ground parts regardless of significant differences in partitioning of dry matter into root and nodule between supernodulating mutants and Sinpaldalkong 2.

• Korean Journal of Microbiology
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• v.24 no.2
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• pp.98-105
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• 1986

Rhizobium meliloti 102 F 51, the symbiotic partner of alfalfa, was mutagenized with N-methyl-N'-nitro-N-nitrosoguanidine (NTG) and UV-irradiation. Three group of mutants which form white, white-pink and red nodules were selected. The adetylene reduction activity, nodulation activity, amount of heme synthesis during the nodulation, and ${\delta}-aminolevulinic$ acid synthetase (ALAS) and ${\delta}-aminolevulinic$ acid dehydratase (ALAD) activities in free living rhizobia and bacteroid states of the each group of mutants were compared. The mutants forming white nodules showed lower acetylene reduction activity compared to those of red nodule forming mutants. The two key enzymes for the heme synthetic pathway, ALAS and ALAD activities of the mutants forming red nodules was much higher than those of the mutants forming white nodules in bacteroid state, however no significant difference was observed in free living state. In the nodules the ALAS was detected only in bacteroid fraction, while ALAD was detected both in bacteroid and plant fraction. ALAS was dramatically increased with the heme synthesis during the nodulation, while ALAD was decreased in plant fraction but slight increase was observed in bacteroid fraction.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.2
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• pp.247-253
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• 1997

Development of soybean cultivars with great nodulation and high nitrogen fixation activity, derived mostly from mutagenesis, may decrease inputs of chemical fertilizer nitrogen into the soil-plant system. Soybean seeds (cv. Jangyupkong, Hwanggeumkong, and Geomjungkong 1) were treated with three different levels of EMS (ethyl methanesulfonate) concentration(30, 50, and 70mM). Increasing the doses of EMS resulted in decreased field emergence rate of seeds, whereas it did not increase M$_2$ mutation frequencies. This indicated that the most efficient concentration of EMS was 30mM for generating mutants. Extensive mutagenesis of Sinpaldalkong 2 with 30mM EMS was undertaken to isolate soybean mutants with greater nodulation. Approximately 8, 200 M$_2$ families were screened for greater nodulation on 5 mM nitrate after inoculation with Bradyrhizobium japonicum strain YCK213-KFCC-10728. Mutant SS-2 nodulated more than the wild type. Comparison of supernodulation between SS-2 and two nts mutants(nts 1007 and nts 1116) revealed that SS-2 showed the supernodulation character at an earlier growth stage than the two nts mutants. Further studies should be needed to characterize the difference in timing of nodulation between SS-2 and nts mutants.

• Journal of Microbiology and Biotechnology
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• v.5 no.2
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• pp.110-113
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• 1995

Transposon Tn5 was used to induce random insertional mutations in Bradyrhizobium japonicum, a soybean endosymbiont. By genomic Southern blot analysis, transposition events were found to have occurred randomly throughout the B. japonicum genome. After screening 3, 626 mutants by auxotrophy test, a histidine auxotroph was isolated. Upon plant infection test, the His mutant showed a 3~4 day delay in nodule formation.

• Proceedings of the Korean Society of Crop Science Conference
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• 1991.05a
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• pp.54-55
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• 1991

• Proceedings of the Korean Society of Crop Science Conference
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• 1991.05a
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• pp.56-57
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• 1991

• The Plant Pathology Journal
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• v.17 no.2
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• pp.67-70
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• 2001

Medicago truncatula is a diploid legume plant related to the forage crop alfalfa. Recently, it has been chosen as a model species for genomic studies due to its small genome, self-fertility, short generation time, and high transformation efficiency. M. truncatula engages in symbiosis with nitrogen-fixing soil bacterium Rhizobium meliloti. M. truncatula mutants that are defective in nodulation and developmental processes have been generated. Some of these mutants exhibited altered phenotypes in symbiotic responses such as root hair deformation, expression of nodulin genes, and calcium spiking. Thus, the genes controlling these traits are likely to encode functions that are required for Nod-factor signal transduction pathways. To facilitate genome analysis and map-based cloning of symbiotic genes, a bacterial artificial chromosome library was constructed. An efficient polymerase chain reaction-based screening of the library was devised to fasten physical mapping of specific genomic regions. As a genomics approach, comparative mapping revealed high levels of macro- and microsynteny between M. truncatula and other legume genomes. Expressed sequence tags and microarray profiles reflecting the genetic and biochemical events associated with the development and environmental interactions of M. truncatula are assembled in the databases. Together, these genomics programs will help enrich our understanding of the legume biology.

• Current Research on Agriculture and Life Sciences
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• v.12
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• pp.57-68
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• 1994

This experiment was conducted to isolate the mutants from S118 and to investigate the physiological characteristics of R. japonicum mutants. The results obtained were as follows; Based on nodulation and acetylene reduction, nodulation of rhizobia was divided into 4 groups, i.e. slow-nodulation, earlier-nodulation, infrequent-nodulation and non-nodulation. At 5% significant level, the growth of inoculated plant with SM255 was bad, but that of HP277 was good. Root-hairs curling was induced by strains S118 and HP277 on soybean, but not by strain SM255. S118 and SM255 were found to be slow-gorwers and produced alkali, whereas strain HP277 was fast-grower and produced acid in YEM broth. In litmus milk reaction, all strains indicated alkaline reaction, and serume-zone was induced weakly by HP277. All of the strains tested in this experiment utilized sucrose. HP277 and LP268 utilized xylose, whereas S118 and SM255 did not. SM255 showed bad growth in nitrogen carriers however utilization of $Ca(NO_3)_2{\cdot}4H_2O$ by HP277 was possible at 25mM and 10mM level. To compare with S118, the protein band of SM255's cell protein electrophoresis was not developed at 0.62 Rm position.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.43 no.1
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• pp.23-27
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• 1998

Inhibition of nodule formation and nitrogen fixation by soil nitrogen, primarily nitrate, is well known in legume plants. The present study was undertaken to evaluate the effect of ${NO_3}^-$ on the nodulation, nitrogenase activity, and growth of supernodulating soybean mutant and its wild type. A greenhouse study was conducted to compare two of supernodulating mutants, 'SS2-2' and 'nts 382', with the normal nodulating cultivar 'Sinpaldalkong 2' when grown in a 1-l styroform cup filled with sand, and fertilized with five levels of ${NO_3}^-$ (0, 2, 4, 8, and 12 mM). During the growth period, each plant was supplied two or three times a week with 50 mL of nutrient solution. Supernodulating soybean mutants, SS2-2 and nts 382, showed more nodules and nodule mass, and greater $C_2\;H_2$ activity than the wild type, Sinpaldalkong 2, regardless of the level of exogeneous nitrogen supply. On the other hand, total dry weight of SS2-2 mutant, which was smaller than Sinpaldalkong 2, did not respond to the various ${NO_3}^-$-N levels. This suggested that supernodulating SS2-2 mutant could maintain fairly high total dry weight at the low ${NO_3}^-$-N level, even in the absence of exogeneous ${NO_3}^-$-N in the nutrient solution. From the reduced top growth and high nitrogen fixing ability of supernodulating mutants, it was surmised that supernodulating mutant could potentially protect agricultural environments from pollution through the reduction in nitrogen fertilization as well as maintain fairly high yield with increasing planting density.