Response of high-yielding soybean varieties to water-saturated and drought stress

BACKGROUND AND OBJECTIVES: The cultivation of soybeans in Indonesia frequently encounters challenges related to water saturation and drought, which ultimately leads to reduced productivity. The objective of this study was to determine how various soybean varieties react to waterlogging and drought in order to identify soybean cultivars that exhibit tolerance to both types of stressors. METHODS: The study was conducted at the greenhouse of the Indonesian Legumes and Tuber Crops Research Institute, spanning from June to August 2022. A factorial randomized block design was employed, utilizing pots as the experimental units, with three replicates. The first factor is the availability of groundwater, namely optimal water available (field capacity), 40 percent of field capacity (drought stress), and water-saturated soil (waterlogging stress). The soybean variety is the second factor to consider, which includes Dering 1 (known for its drought tolerance), Dering 2 (also drought tolerant), Deja 1 (tolerant to water saturation), Deja 2 (also tolerant to water saturation), Devon 1 (noted for its high isoflavone content), and Dega 1 (specifically adapted for irrigated lowland conditions). FINDINGS: The results showed that Dering 2 and Deja 2 varieties grown in soil moisture levels at 40 percent field capacity were capable of achieving similar growth outcomes in terms of plant height, shoot/root ratio, number of pods per plant, seed yield, and 100 seed weight compared to those grown in optimal soil moisture conditions. The stress tolerance index of the two varieties in the soil moisture at 40 percent of field capacity reached 1.03 and 0.83, respectively. The yields of Dering 2 and Deja 2 varieties at the optimal soil moisture reached 4.53 gram per plant and 6.28 gram per plant, and in soil moisture of 40 percent field capacity were 4.68 gram per plant and 5.69 gram per plant respectively. In flooded soil, the Dering 2 and Deja 1 varieties can develop the weight of 100 seeds, number of branches, and plant height as same as in optimal soil moisture, with relatively lower yield reduction compared to other varieties, with stress tolerance index values of 0.66 and 0.54. CONCLUSION: The Dering 2 and Deja 2 cultivars exhibit tolerance to drought stress levels of up to 40 percent of field capacity, whereas the Dering 2 and Deja 1 cultivars demonstrate tolerance to water-saturated soil. A noteworthy finding is the identification of soybean cultivars capable of thriving in both drought and waterlogged environments, exemplified by the Dering 2 variety. Originally bred to combat drought-related challenges, the Dering 2 cultivar has shown promising results in waterlogged soil conditions as well. Similarly, the Deja 2 variety, which was designed and released for water-saturated environments, was found in this study to be tolerant of drought conditions.