In the absence of exogeneous nitrogen supply, evaluation of a symbiosis effectiveness of Bradyrhizobium japonicum USDA 110 in a supernodulating soybean mutant, SS2-2, its wild type, Sinpaldalkong 2, and control genotype, Jangyeobkong, was conducted in this study. Nodules in SS2-2 were initially white and similar to its wild type, Sinpaldalkong 2. At the late stage, the wild type nodules became dark pinkish by maturation, by contrast, mature nodules in SS2-2 remained light green to pinkish, indicating a lack of leghemoglobin. Tap root length was short in nodulated symbiotic SS2-2 than that of its wild type and the control genotype. Nodulated root length and nodule density on root length were significantly increased by B. japonicum inoculation, but no significant increase was observed on root length and percentage of nodulation to total root length. Regardless of Bradyrhizobium inoculation, SS2-2 showed higher nodule dry weight and higher acetylene reduction activity (ARA) when compared with its wild type and the control genotype. Inoculation of B. japonicum leaded the increase of ARA in 47 days after planting (DAP), in part because of nodule development. Supernodulating mutant, SS2-2, less responded to B. japonicum induction in terms of nitrogen fixation and nodulation characteristics than its wild type. Thus, interaction of supernodulating soybean mutant with Bradyrhizobium had less symbiotically associated response than normal nodulating soybean.

Rehmannia glutinosa is one of the most important medicinal crops in Korea. However, various plant pathogens including Fusarium sp. cause great damages and cause enormous economic losses. Therefore, this study was conducted to select Fusarium resistant plants by using mutagen-treated Rehmannia glutinosa. The plant material used was a native accession of Rehmannia glutinosa. As a result, among the Rehmannia glutinosa treated with various concentrations of EMS, R. glutinosa treated with 0. 03M EMS showed higher resistance against infection of F. oxysporum in pot tests, and Rehmannia glutinosa plants treated with 0.12M EMS showed higher resistance against infection of F. oxysporum in field tests.

In this experiment, three kinds of mutations(ge, re, and eml )relating to the size of embryos were used to study their generation, genetic mechanism and developmental characteristics, and the interactions between embryo and endosperm were also examined. Giant embryo mutation comprises 7 kinds including the already isolated ge, and ge-2, which share an identical gene site. The SAM and the size of radicule for the ge showed little difference compared to a normal type. The number of embryo cells did not increased as much as it would affect the size of embryo. Therefore, the enlargement of embryo was due to the enlargement of scutellum that originated from the corpulence of each cell. Both F1' s of re ]and odm 49 formed reduce embryos, and other combinations of hybridization showed all wild type of embryo sizes. Accordingly, the odm 49 must have an identical gene site of re 1, while odm 48 and odm 62 have different gene sites. Their shoots and radicules also shrank by the same ratio, however no sign of physical change was noticed. The size of embryo cell showed no change, while the number of cells was the half of that of wild types. The three gene sites of re represent all of them control the size of the entire embryo forming organs. The eml 1 was defined to have temperature sensibilities that the generation of endosperms was active at a high temperature while that was hampered at a low temperature.

Hypernodulation soybean mutant, SS2-2, is characterized with greater nodulation and nitrogen fixing ability in the root nodule than its wild type, Shinpaldalkong 2. The present study was performed to identify a genetic locus conferring hypernodulation in soybean mutant SS2-2 and to determine whether the gene controlling the hypernodulation of SS2-2 is allelic to that controlling the supernodulation of nts382 mutant. Hybridization studies between SS2-2 and Taekwangkong revealed that the recessive gene was responsible for the hypernodulation character in soybean mutant SS2-2. Allelism was also tested by crossing supernodulating mutant nts382 and hypernodulating mutant SS2-2 that both hypernodulation and supernodulation genes were likely controlled by an identical locus. Molecular marker mapping of hypernodulation gene in SS2-2 using SSR markers confirmed that the gene conferring hypernodulation was located at the same loci with the gene conferring supernodulation. It is interesting to note that the same gene controlled the super- and hyper-nodulation characters, although SS2-2 and nts 382 exhibited differences in the amount of nodulation in the root system. Further genetic studies should be needed to clarify the genetic regulation of super- and hyper-nodulation in soybean.