We have conducted this study to select soybeans adaptable to North Korea using growing degree days (GDD) as a heuristic tool. For analyzing climatic conditions, we assumed that climatic conditions of Longjing, Donggang, and Yeoncheon are similar to the Eastern Coast Northern Zone, Suyangsan Northern Zone, and Suyangsan Southern Zone in North Korea, respectively. The predicted days to flowering of 100 soybeans grown at Longjing, Donggang, and Yeoncheon were in ranges from 7/17 to 7/30, from 7/16 to 7/28, and from 7/30 to 8/10, respectively, while the last date of flowering for completely harvesting were predicted by July 12th, August 2nd, and August 11th, respectively. The predicted days to flowering using GDD were almost similar to the days investigated in the three fields. These results showed that GDD is highly effective in predicting development rates of soybean, such as days to flowering and days to maturity. Although most of the tested soybeans were difficult to adapt to Longjing, we selected 12, 15, and 16 soybean varieties/lines based on the predicted days to flowering and last date of flowering for completely harvesting and yield of the soybeans grown at Longjing, Donggang and Yeoncheon, respectively, for further analyzing effects of the regional characteristics on agricultural traits of the selected soybeans. The 100-seed weight and yield of the selected soybeans grown at Longjing was significantly low compared with those at the other locations. The results implied that the soybeans would be exposed to freezing temperature before R6 stage and the reduced size would contribute to soybean yield loss. Taken together, we concluded that Suwon212, Iksan13 and ‘Shinpaldalkong2’ which were stable in degree of lodging, 100-seed weight, and yield at Donggang and Yeoncheon could be adaptable to Suyangsan Northern Zone, and Suyangsan Southern Zone in North Korea.
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First pod height (FPH) is an agronomic trait for the mechanical harvesting of soybeans with combines. The seed loss could be minimized, if the FPH is higher than the height of the cutter bar in combines. Hence, developing soybeans with high FPH has become one of important breeding goals in current crop improvement programs. The
objective
of this study was to evaluate genetic and environmental variation of FPH in soybean and to analyze the effect of ratio of FPH to plant height (PH) on seed yield. Four genotypes were evaluated across six different environments to analyze environmental variation of agronomic traits including FPH. Three F2 populations were evaluated to analyze genetic variation and relationship between the ratio of FPH to PH and seed yield. The main effects of planting distance, genotype and seeding date were significant for FPH, but FPH is affected more by genetic factors than by environmental factors. The mean heritability value of FPH was 66% across three F2 populations. Seed yield was found to reduce with increase in the FPH/PH ratio. In conclusion, genetic factors have effect more than environments to the variation of FPH. While FPH is higher than cutting height, the smaller ratio can minimize seed yield decrease.
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