Gun-Ho Jung

Effects of Waterlogging on Nitrogen Fixation and Photosynthesis in Supernodulating Soybean Cultivar Kanto 100

Abstract The supernodulating soybean (Glycine max (L.) Merr.) cultivar Kanto 100 was previously characterized by superior nitrogen (N) fixation and photosynthesis, and resulting in high yields. However, this cultivar seems to be susceptible to waterlogging during the vegetative growth stage, which frequently occurs in major soybean producing areas in East Asia. The objective of this study was to compare the effects of waterlogging on nodulation, N fixation and photosynthesis in Kanto 100 with those in its normally-nodulating ancestral cultivar Enrei. Kanto 100 and Enrei were grown in pots, and subjected to waterlogging for 10 days at three vegetative growth stages in 2003 and 2004. Waterlogging significantly reduced the number of nodules of both cultivars, but the magnitude of the reduction was more pronounced in Kanto 100. The acetylene reduction activity (ARA) of nodules and apparent photosynthetic rate (AP) of leaves were generally depressed immediately after the start of waterlogging, but both functions recovered substantially at the pod-filling stage in both cultivars. No marked cultivar difference was found in the magnitude of the reduction of ARA per plant and AP measured immediately after waterlogging and at the pod-filling stage in both years, but growth impairment was more pronounced in Kanto 100 in 2003. These results suggest that the supernodulating cultivar Kanto 100 is more susceptible to waterlogging than its normally-nodulating ancestral cultivar.

Effect of Waterlogging During Vegetative Stage On Growth And Yield in Supernodulating Soybean Cultivar Sakukei 4

Abstract The Supernodulating Soybean Cultivar Sakukei 4 Was Previously Characterized By Its Superior Capabilities of Nitrogen (N) Fixation and Photosynthesis, and Was Expected To Be High Yielding. Since The N Absorption By Sakukei 4 Is Largely Dependent On N Fixation, It May Be Strongly Affected By Waterlogging During The Vegetative Stage, Which Occurs Frequently in Major Soybean Producing Areas. in This Study, We investigated The Reduced Growth and Yield Resulting From Waterlogging DuringVegetative Stage and The Subsequent Recovery in Sakukei 4, in Comparison With Those in The Normally-Nodulating Cultivar Enrei and Non-Nodulating Genotype En1282. Under The Field Conditions, The Reduction of Growth and Yield By Waterlogging Was Greatest in En1282 Among The Three Genotypes, indicating That Capability of N Fixation Is Essential For The Recovery From Waterlogging-induced injury. The Waterlogging-induced Yield Reduction in Sakukei 4 Resembled That in Enrei, Although Growth Reduction Was Greater in Sakukei 4 Than in Enrei. Irrespective of Cultivar, The Yield Was Associated More Closely With The Crop Growth Rate (Cgr) During The Post-Treatment Stage Than With That During The Waterlogging Treatment. in The Pot Experiments, Yields Positively Correlated With Both Above- and Underground Plant Parts Irrespective of Cultivar, Not Significantly, But Significantly With Root Dry Weights in Enrei and With Nodule Dry Weights in Sakukei 4. These Results indicate That Sakukei 4 Exhibits A Marked Decrease in Dry Matter Production By Waterlogging, But Yield Decrease Is Compensated To A Level Similar To That of Enrei Because of Its Enhanced Nodule Growth During The Recovery Stage.