Renewable energy generation has attracted growing interest globally. The agro-photovoltaic (APV) system is a new alternative to conventional photovoltaic power plants, which can simultaneously generate renewable energy and increase agricultural productivity by the use of solar panels on the same farmland. The optimization of crop yields and assessment of their environmental sensitivity under the solar panels have not yet been evaluated with various crop species. This study aimed to evaluate the agronomic performances and crop yields under the APV system and the open field with crop species such as rice, onion, garlic, rye, soybean, adzuki bean, monocropping corn, and mixed planting of corn with soybean in South Korea. The results indicated that there was statistically no negative impact of the APV system on the forage yield of rye and corn over two years, suggesting that forage crops under the APV system were suitable to producing forage yield for livestock. In addition, the measured forage quality of rye was not significantly different between the open field and the APV system. However, rice yield was statistically reduced under the APV system. The yield of legume crops and vegetables in this study did not show consistent statistical results in two years. For further study, crop yield trials will still be required for rice, soybean, adzuki bean, onion, and garlic for multiple years under the APV system.

Soybeans (Glycine max (L.) Merr.) with black seed coats and green cotyledons are rich in anthocyanins and chlorophylls known as functional nutrients, antioxidants and compounds with anticarcinogenic properties. Understanding the genetic diversity of germplasm is important to determine effective strategies for improving the economic traits of these soybeans. We aimed to analyze the genetic diversity of 470 soybean accessions by 6K single nucleotide polymorphic loci to determine genetic architecture of the soybeans with black seed coats and green cotyledons. We found soybeans with black seed coats and green cotyledons showed narrow genetic variability in South Korea. The genotypic frequency of the d1d2 and psbM variants for green cotyledon indicated that soybean collections from Korea were intermingled with soybean accessions from Japan and China. Regarding the chlorophyll content, the nuclear gene variant pair d1d2 produced significantly higher chlorophyll a content than that of chloroplast genome psbM variants. Among the soybean accessions in this study, flower color plays an important role in the anthocyanin composition of seed coats. We provide 36 accessions as a core collection representing 99.5% of the genetic diversity from the total accessions used in this study to show potential as useful breeding materials for cultivars with black seed coats and green cotyledons.

Drought is a significant abiotic stress that limits crop production. Soybeans [Glycine max (L.) Merr.] are regarded as drought-sensitive. In the present study, the drought responses of wild soybean accessions were evaluated at different growth stages. Based on the leaf wilting index of 411 accessions at the vegetative stage, seven highly tolerant (HT) and 24 tolerant (T) accessions were identified, although most wild soybeans were classified as moderate (M), sensitive (S), and highly sensitive (HS) genotypes. In addition, with selected wild soybeans, stomatal density decreased in HT accessions but increased in HS accessions under drought conditions at the vegetative stage. However, for cultivated soybeans, the stomatal density of the drought-tolerant and drought-sensitive were not significantly different between the two conditions. The expression levels of drought-related transcriptional factors indicated that the HT genotype showed a higher expression level of drought-related genes than that of the HS genotype at the vegetative stage. At the reproductive stages, 12 wild soybeans randomly selected from HT, T, S, and HS based on assessment at the vegetative stage showed consistent drought responses with seed yield, root development, and water status. However, the extent of the detrimental effect of drought on the germination rates and root length of 165 wild soybeans at the germination stage varied depending on the genotype, indicating that there may not be a robust correlation between phenotypic measurements at the germination stage and drought-related assessments at the two growth stages. The information from this study can provide useful breeding materials for the development of drought-tolerant cultivars from wild soybeans.

Stomatal observation and automatic stomatal detection are useful analyses of stomata for taxonomic, biological, physiological, and eco-physiological studies. We present a new clearing method for improved microscopic imaging of stomata in soybean followed by automated stomatal detection by deep learning. We tested eight clearing agent formulations based upon different ethanol and sodium hypochlorite (NaOCl) concentrations in order to improve the transparency in leaves. An optimal formulation—a 1:1 (v/v) mixture of 95% ethanol and NaOCl (6–14%)—produced better quality images of soybean stomata. Additionally, we evaluated fixatives and dehydrating agents and selected absolute ethanol for both fixation and dehydration. This is a good substitute for formaldehyde, which is more toxic to handle. Using imaging data from this clearing method, we developed an automatic stomatal detector using deep learning and improved a deep-learning algorithm that automatically analyzes stomata through an object detection model using YOLO. The YOLO deep-learning model successfully recognized stomata with high mAP (~0.99). A web-based interface is provided to apply the model of stomatal detection for any soybean data that makes use of the new clearing protocol.

Soybean is one of the most important crops widely used as food, feed, and industrial products. Weeds compete with the crops for light, nutrients, water, space, and other growth requirements, causing an average yield reduction of 37% in soybean. Bentazone is an herbicide that selectively kills broadleaf weeds by inhibiting photosynthesis. It is widespread in soybean-cultivating areas including genetically modified organism (GMO) and GMO-free regions all around the world. This herbicide carries a double-edged sword since it can also incur damage to crops upon application. The challenge, therefore, lies in the deliberate selection of bentazone-tolerant cultivars. We systematically analyzed several factors that affect the metabolism of bentazone in soybean, such as phenotypic and genotypic differences among soybean accessions, the time and method of application, the absorption and metabolism of bentazone in soybean, and the effects of effective application and cultivar selection on yield and crop injury. Furthermore, we recommend that further studies should be done in aid of discovering more tolerant soybean cultivars. We hope that our review will help farmers and soybean producers, as well as geneticists, in developing bentazone-tolerant soybean cultivars to improve the global yield of soybean crops as a response to the ever-dynamic food demand across the globe.