Vegetable soybeans [
Glycine max (L). Merrill] (2n=40), a member of the
Fabaceae family, is gaining attention in agriculture and nutrition science due to their exceptional nutrient density and potential health benefits. It is commonly referred as Edamame (Japan), ‘Poot Kong’ (Korean), Maodou (china), green soybean, edible soybean (North America and other part of the world). The global edamame landscape in 2024 reflects a highly specialized production footprint, totaling 1.05 to 1.15 million metric tons grown across 210,000 to 250,000 hectares. China remains the leader, with a production volume of 750,000 to 900,000 metric tons and a cultivated area exceeding 180,000 hectares focused on both domestic and global markets. Taiwan as a premium producer, generating 75,000 to 85,000 metric tons primarily for the high-end Japanese export market, while Thailand utilizes roughly 8,000 to 10,000 hectares to support its robust frozen processing industry. In the United States, production has reached 30,000 to 40,000 metric tons to meet growing domestic demand for fresh and frozen products. Meanwhile, Vietnam and other emerging regions contribute an additional 40,000 to 50,000 metric tons, signaling a diversifying global export market for this high-value specialty crop (
USDA FAS, 2024;
FAOSTAT, 2024;
Nair et al., 2023). Unlike field soybeans primarily used for oil extraction and animal feed, vegetable soybean harvested for immature pod or green pod at R6 stage
(Gao et al., 2024 and
Nair et al., 2023) offering a unique flavor, softer texture and a rich source of nutrients. Vegetable soybeans are popular in East Asian cuisines
(Shilpashree et al., 2021). Pods can be sold in markets as fresh vegetable, frozen and canned products
(Nair et al., 2023) also its gaining traction in global markets as a healthy snack and ingredient particularly among health-conscious individuals seeking plant-based protein sources. The quality of vegetable soybean can be categorized into three key characteristics like eating quality (taste, texture, flavor and aroma), appearance quality (pod size, shape, color and uniformity) and nutritional quality
(Wang et al., 2024; Wang et al., 2023 and
Zhang et al., 2017). Vegetable soybean provides all essential amino acids with significant levels of dietary fiber, vitamins, minerals and bioactive compounds such as isoflavones and polyunsaturated fatty acids (Table 1). Despite its potential, production remains concentrated in a few countries, in India, it is still at a nascent stage (
Nagalakshmi et al., 2015). Due to its exceptional nutritional composition and unique taste, the cultivation of this crop has experienced a substantial increase in interest across various regions beyond East and Southeast Asia over the past decade
(Nair et al., 2023). The crop contributes to agricultural sustainability due to the ability to fix atmospheric nitrogen in association with Rhizobia, enriching soil fertility. There are several challenges and limitations in the production of vegetable soybean such as limited genetic resources, hinder the development of varieties suited to diverse growing regions or tailored to meet local taste preferences, also high water requirement restrict production expansion to areas with sufficient water availability
(Nair et al., 2023), seed size, seed coat characteristics and chilling injury also interact to influence soybean emergence and vigor. Seedling establishment is influenced by multiple abiotic and biotic factors. Targeted research and development is needed to overcome production constraints and support sustainable growth in vegetable soybean farming. This review investigates the potential of vegetable soybeans, focusing on the challenges related to the limitations in the production, highlights future research directions, emphasizing that, vegetable soybeans could significantly contribute to Indian agriculture, providing both economic and nutritional advantages for farmers and the nation as a whole.
Global and Indian landscape of vegetable soybean: current trends and insights
Globally, vegetable soybean production is dominated by countries in East Asia, where the top leading producers of vegetable soybeans are China, Japan and Taiwan, while the primary consumers include China, Japan, Korea, USA, Taiwan, Thailand and Europe
(Nair et al., 2023). Thailand and Taiwan are major exporters, supplying frozen Edamame to Europe and North America (
Global edamame market review, 2021). According to a case study, awareness among farmer’s and efficient contribution can lead to higher productivity and profitability for an example Indonesia faces challenges due to weaker systems for managing orders and deliveries due to inefficiencies in the farmers’ groups, whereas in Thailand, structured contract farming approach enhances efficiency and export success
(Marimin et al., 2010). Vegetable soybeans have become the second largest soy food consumed in the USA at 25,000 to 30,000 t annually (
Nair et al., 2023). Interestingly rising interest in plant-based diets has boosted the demand in the global market, over a period of 20 years in Indonesia, the total harvested area of vegetable soybeans has increased from 30.5 ha to 1417 ha till 2017 in Indonesia due to its demand for export
(Nair et al., 2023). In India, the cultivation of vegetable soybeans is concentrated in a few select regions and its overall production remains limited (
Ministry of Agriculture and Farmers Welfare, 2020). The “ICAR Research Complex for Eastern Region” and the “Farming System Research Centre for Hill and Plateau Region” in Plandu, Ranchi, Jharkhand, developed the improved vegetable soybean variety “Swarna Vasundhara”, which was released by the “Crop Variety Release Committee (CVRC)” for commercial cultivation (Annual Report 2022, ICAR-IISR and
Ravishankar et al., 2016). Vegetable soybean variety KBVS-1 (KARUNE) released for cultivation by UAS Bangalore in the year 2021 and recommended for southern zone of India like Andhra Pradesh, Tamil Nadu and few reasons of Maharashtra. Moreover, despite its nutritional benefits and potential as a cash crop, its cultivation remains constrained by several factors
(Patil et al., 2018).
The concentration of isoflavones is highly variable, depending heavily on genotype (variety) and environmental growing conditions. High concentrations of genistein are directly correlated with increased bitterness and astringency in the flavor profile. However, they are also responsible for sensory attributes such as bitterness
via the stimulation of $hTAS2R14$ and $hTAS2R39$ receptors
(Roland et al., 2011).
Unleashing the culinary potential of vegetable soybean: Recipes and Health Benefits
Vegetable soybean can be consumed directly as garden pea
(Ravishankar et al., 2016) also offers versatile culinary applications (Fig 1). To prepare the boiled snack harvest the pods, boil in water for 7-10 minutes (optionally with salt), then immerse in ice-cold water for 1-2 minutes to stop cooking. Drain and serve cold. For vegetable side dish, try tossing them with olive oil and a light sprinkling of salt. Cooked beans are also a versatile ingredient, for boosting the texture and protein content of salads or mixed vegetables. They are equally valuable in stir-fries and can be incorporated into soup, whether homemade, canned, or dried. It can be processed into soymilk and diverse foods including roasted nuts, yogurts, ice-cream, tofu and tempeh (Fig 1). Isoflavones like daidzein and genistein are benefiting both plants (by enhancing defense and symbiosis) and humans by supporting hormonal balance, heart health, bone strength and potentially reducing cancer risk
(Messina et al., 2001; Lee et al., 2004). According to the
Foodstruct (2026) nutrition database, the health benefits of edamame are categorized by its unique nutrient density compared to mature soybeans and other legumes. As a “complete protein,” it provides all essential amino acids necessary for muscle maintenance, particularly in plant-based diet. Unlike dried soybeans, edamame retains Vitamin C and is exceptionally high in Folate (B9), which is critical for DNA synthesis and preventing neural tube defects during pregnancy (Table 3). High levels of fiber and soy isoflavones (genistein and daidzein) work to lower LDL cholesterol, improve lipid profiles and reduce risks of atherosclerosis and hypertension. Its low-glycemic index (GI) ensures stable blood sugar levels, making it ideal for metabolic health. Rich in Calcium, Magnesium and Phosphorus, edamame supports bone mineral density (Table 3). Its isoflavones further help reduce osteoporosis risk in post-menopausal women (Table 2).
Key morphological traits and optimal harvest timing for vegetable soybean
Soybeans, as short-day plants, initiate flowering with long nights. When a soybean plant begins to flowering, they enter the reproductive (R) growth stage, categorized into stages R1 (first flower bloom) to R8 (full maturity) as indicated in the Fig 2. During stages R1 to R4 plants adjust the number of flowers and young pods based on environmental conditions. Soon after R5 stage it starts to fill the small seeds and continues to begins the R6 stage of the development at this time it is very important to ensure that crop continues to be managed thus it is critical period for irrigation and pest management
(Purcell et al., 2021).
Moreover, it is the peak harvesting time for vegetable soybean when the beans reach the R6 stage, with pods 80-90% filled and bright green in color as shown in Fig 3 (a) and (c). Yellowing of pod indicates the physiological changes within seed deterioration of nutritional quality (when sugar converting into starch, consequently changes the taste that is unacceptable to consumers) and unsuitable for fresh market
(Zeipina et al., 2017). Vegetable soybean typically matures uniformly, resulting in the entire crop being ready for harvest simultaneously. The peak harvest often lasting just 3 to 4 days (
Masuda, 2004), necessitating careful planning and prompt action to ensure optimal quality and yield. Since, pods of vegetable soybean can have 1-3 seeds per pod it can be considered as desirable morphological quality to have at least 2-4 seeds per pod along with large size of pods and seeds with bright green colour. However, texture of the pod (pubescence absent on pod surface) is also a major attribute (Fig 3), which is more acceptable to consumers because of the clean appearance after cooking
(Shanmugasundaram et al., 2015). Additionally, the nutrient content and eating quality like sweetness, texture and flavor is the most desirable.
Progress and challenges in the development of ideal vegetable soybean varieties
Genetic diversity of vegetable soybean and recent advancement
Dong et al. (2014) studied 100 vegetable soybean accessions to evaluated genetic diversity and population structure by using 53 simple sequence repeat (SSR) markers and found 98% similarity among the all germplasm collected from China, Taiwan and Japan. Similarly, different researchers also reported the narrow base of vegetable soybean for example
(Mimura et al., 2007), also used 17 SSR markers to assessed the diversity of 130 vegetable soybean accessions and observed narrower genetic base of Japanese vegetable soybeans compared to the Chinese vegetable soybeans. Meanwhile, population structure and genetic diversity study in soybean
(Chiemeke et al., 2024) shows high and positive contribution of days to 50% flowering, days to maturity, yield, shattering score and lodging score to the total variation. Also Phenotype-based core collections (
Nair et al., 2023) can retain diversity and genetic variability of vegetable soybeans, this could be helpful for breeders. Understanding genetic diversity offers essential insights for selecting parents and developing an efficient hybridization strategy. High-throughput phenotyping has been applied to soybean research to study traits such as leaf shape
(Chen et al., 2004), root structure
(Fenta et al., 2014) and canopy coverage
(Xavier et al., 2017). Moreover,
(Dhakal et al., 2021) established a phenotyping pipeline for collecting images of vegetable soybean at the harvest stage (R6 to R7) to quantify major shoot architecture traits related to harvest efficiency, including plant height, branching patterns, pod numbers and pod locations. Recently (
Gao et al., 2024) conducted a genome-wide association study on 188 vegetable soybean accessions and identified four candidate genes related to pod number of vegetable soybean (Glyma.03g183200), fresh pod weight (Glyma. 09G102300 and Glyma.09G102200) and plant height (Glyma.13G109100) from vegetable soybean germplasm.
(Yu et al., 2021) re-sequenced the vegetable soybean varieties that are Taiwan-75, Zhexi- andou No. 8, Zhexian No. 9 and Zhexian No. 10, in which cluster analysis using SSR analysis shows the close relationship. Despite of this the average heterozygosity rate of the SNPs was 11.99% among these four, likewise found genetic variation on the chromosomes. Out of 23,371 identified genes a total of 282 genes were related to carbohydrate metabolic processes. These genes and QTLs could help to design the desired type of vegetable soybean varieties through marker-assisted breeding and with help of forward and reverse genetic approaches.
Suitable varieties
In vegetable soybean one of the key challenges limiting the commercial production is the lack of locally adapted varieties
(Djanta et al., 2020; Zhang et al., 2013). The World Vegetable Center, Taiwan has developed a significant number of enhanced breeding lines
(Nair et al., 2023), have been utilized by various countries to create and release improved and regionally adapted varieties for cultivation, including North and South America, Europe, Africa
(Konovsky et al., 1994; Nair et al., 2023). Countries like Japan and the USA are advancing breeding programs to improve pod size, sweetness, seed uniformity and pest resistance
(Kim et al., 2020). These efforts are crucial for meeting the increasing global demand for high-quality vegetable soybean. Recently, seven improved vegetable soybean germplasm lines were released.
i.e., LB18-49, LB18-52, LB18-57, LB18-58, LB18-65, LB18-67 and LB18-75, where ‘Tohya’,‘BeSweet 2001’, ‘Gardensoy 24’ and ‘Gardensoy 41’ served as recurrent parents with pest-resistant donor lines to develop large-seeded, pest-resistant soybean lines that will be valuable for breeders in the U.S. for developing desired cultivars
(Bowen et al., 2022; Nair et al., 2023). More over Researchers found that exotic varieties showed poor seedling emergence in different countries like Australia, the USA and Uganda (
Williams et al., 2015;
Tsindi et al., 2019) and India
(Kuchlan et al., 2023) which indicate that there is need for development of varieties having desirable traits and can grow in the specific climatic conditions. For example, there is a number of variety which introduced from the Japan and Korea were found to be prone to pod shattering which is a concern for seed production in the Midwest USA
(Bernard et al., 2001). High pod set for mechanical harvesting are also key goals in China, researchers are initiating to develop better varieties to enhance mechanical harvesting efficiency which includes plant type and height of the lowest pod per plant
(Zhang et al., 2017).
Seed characteristics
In china extra-large seed variety (SX6) was identified, which is 40% larger than the slandered variety AGS292 this will be valuable for developing new lines. G10427 is the best genotype specifically for Uganda fulfilling all desired characteristics like large seed size, high yield and adaptability to local conditions
(Tsindi et al., 2019). However, main focus on selection by famers is seed germination and storability, because large seed have low germination due to several factors in this review. Globally consumer preference is also essential for attracting people and ensuring market success, flavor remains a significant focus, emphasizing sweetness and unique taste (for organoleptic acceptance) can enhanced by the combination of compounds such as ascorbic acid, sucrose, glutamic acid and alanine, with cis-jasmone and (Z)-3-hexenyl acetate also contributing to its desirable taste (
Masuda, 1991) and sweetness can be enhanced by increasing the concentration of sweetness-imparting soluble carbohydrates (maltose) in seeds
(Nair et al., 2023) targeted breeding strategies can be a promising approach to enhance flavor.
Jha et al. (2021) reported three QTLs which are proximity of functional genes responsible for biosynthesis of enzymes, which are involved in the breakdown of starch into maltose. It can be potentially useful in marker-assisted breeding for development of high maltose content soybean genotype. Additionally, minimizing pod shatter is critical for seed production, whereas easily opened pods are preferred for fresh consumption. JLM010 a very high yielding vegetable type soybean recommended for Jaboticabal region in Brazil producing fresh weight of 136.04 g of pods per plant and 92.52 g of fresh weight/100 seeds and 11.12 t/ha of total immature seeds (
Nair et al. 2023), with better functional properties can be utilize in Breeding program for improving pod yield in low yielding lines. In India vegetable type soybean variety namely Karune is released from CVRC system. The main problem to grow this variety in central zone which is hub of soybean is its poor seed germination ability (40%) takes longer time for pod development and even if the field emergence takes place well, the variety is very much susceptible to diseases which drastically reduce the seed production of this variety
(Kuchlan et al., 2023). This issue is being address at National Institute of Soybean Research Indore, India. Recently NRC 188 has been released for cultivation in central zone of India.
Key constraints limiting vegetable soybean production
Major problem of vegetable soybean is emergence following are the influential factors affecting seed emergence.
Germination and temperature
In vegetable soybean poor germination is a major problem, germination takes about four days at optimal temperatures (27-30
oC), whereas it can take two weeks or more in cold soil or about 10
oC low temperature
(Purcell et al., 2021). Sánchez et al. (2005) found that the day/night temperature of 70/60
oF ideal for seedling emergence.
Hosono et al. (2010) conducted a study in Japan and reported that vegetable soybean sown early in the season can be negatively affected by low night temperatures which inhibit seed germination and early seedling development. The study suggested that mulching helps address this issue by increasing soil temperature and minimizing fluctuations in soil moisture. In contrast, in India, high daytime temperatures during the same period can induce thermal stress in crops, necessitating the implementation of irrigation strategies and the adoption of heat-tolerant agricultural practices to maintain crop growth and productivity.
Seed size
Vegetable soybean seeds are 65-100% larger than grain soybean seeds, influencing hydration, emergence and seedling growth
(Crawford et al., 2018). Smaller seeds emerge faster (10%) due to quicker hydration, while larger seeds, requiring more water, are more sensitive to water stress
(Rezapour et al., 2013; Kering et al., 2015). Large seeds also face greater soil resistance during emergence, particularly in compacted soils and have higher rates of cracked seed coats (
Nangju, 1979), reducing germination potential.
Seed coat characteristics
The seed coat protects the embryo and regulates water uptake, affecting germination and seed longevity. Soybean seed coats are highly hydrophilic, absorbing up to 3.8 times their fresh weight in water (
Powell, 1986 and
Li et al., 2022). Wrinkles on seed coats or cracks negatively affects the germination
(Li et al., 2022), increasing microbial growth and electrolyte leakage (
Mohamed-Yasseen et al., 1994). The thickness of the seed coat also affects its permeability, which in turn influences the speed and success of germination (
Noodén et al., 1985 and
Li et al., 2022). Large seeds often deteriorate faster than smaller ones in the storage longevity of the seeds is influenced by combination of genetics, maturity and quality of the seeds during harvesting timing, moisture content of the seed and storage temperature
(Shelar et al., 2008).
Plant depth
Planting depth also affects the seed emergence, deeper planting delays emergence, increases risks like soil-crusting and lowers emergence rates
(Crawford et al., 2019). It’s totally depends on grain type, soil type and weather conditions like rainfall and temperature
(Li et al., 2022). Zhang et al. (2013) suggested shallower planting around 3 cm is ideal for the vegetable soybean.
Seed and seedling diseases
Soil borne pathogens like
Rhizoctonia solani, Fusarium species,
Phytophthora sojae and
Pythium species are common in edamame similar to grain soybeans it can lead to significant yield loss (
Williams et al., 2017;
Allen et al., 2017 and
Xue et al., 2007). Seeds of vegetable soybean with their higher sugar content and larger size leach more nutrients into the soil, attracting pathogens and increasing seedling mortality (
Finch-Savage et al., 2016;
Li et al., 2022. Fungicide treatments can help but must be used judiciously, especially with increasing interest in organic farming. Biological treatments show promise but need further study. Some bacterial strains, such as
Bacillus subtilis, “
Pseudomonas putida”,
Streptomyces species and
Trichoderma harzianum have shown effectiveness in controlling soil borne diseases and improving seedling emergence in grain soybean (
Reznikov et al., 2016;
Paulitz et al., 1992 and
Xiao et al., 2002). In India, recently developed varieties like Karune and Swarna vasundhara are susceptible for diseases are a major constraint in the expansion of the vegetable soybean. Additionally, studies on disease resistance in vegetable soybean cultivars have shown varying susceptibility, highlighting the need for further research to develop disease-resistant varieties.
Secondary metabolites in soybean
Secondary metabolites in vegetable soybeans are essential not only for the plant’s defense but also for their nutritional content, including protein, lipids, fiber, essential amino acids and micronutrients such as vitamins and minerals (
Masuda, 1991). These compounds contribute to the health benefits of soy-based foods. Despite of gaining reputation as superfood it has anti nutritional factors (trypsin inhibitors) that affect the quality and preferences, trypsin inhibitor (TI) has been reported to be present at the R6 growth stage
(Kumar et al., 2005) in both grain-type and vegetable soybeans which basically inhibit the activity of “trypsin”, an enzyme essential for protein digestion in the small intestine and Kunitz trypsin inhibitor (KTI) is completely synthesized as the soybean plant reaches the R6 stage
(Nair et al., 2023). However, KTI is heat sensitive so, it easily inactivated completely by moist heat treatment during cooking or processing due to the presence of only 2-disulfide linkages. In the case of vegetable soybeans, secondary metabolites like flavonoids and phenolics are produced in response to microbial or herbivorous threats, contributing to the plant’s defense system and potentially impacting the nutritional profile of the harvested product
(Shanmugasundaram et al., 1991).
Quality characteristics impacting the marketability of vegetable soybean
The quality of vegetable soybeans is influenced by a number of factors, such as genotype, harvest timing, crop growth stage and environmental conditions
(Mbuvi et al., 1995). Among these, the time of harvest plays a critical role in determining both consumer acceptability and marketability of fresh vegetable soybeans. However, the physical and organoleptic properties are key factors to determine the marketability (
Masuda, 1991;
Shanmugasundaram et al., 1991). The optimal harvest time (R6 growth stage) is a delicate balance between achieving the best product quality and critical for ensuring yield. Quality traits such as color of pod, texture and seed size are all affected by the development time
(Mbuvi et al., 1995). Among physical characteristics, the appearance and size of the pods and seeds are particularly important. High-quality pods are typically bright green and at least 5.0 cm in length and 1.4 cm in width
(Kumar et al., 2005). Large seed size (50-60 g/100 pods), glabrous pod and attractive unblemished green colour considered to tempt a premium price in the market. Varieties that align with consumers’ taste and culture, like the creamy and beany flavor (preferred by Thai consumers) and sweetness, large seed (preferred in Australia) can significantly boost acceptance and demand for example variety “Sayamusume appreciated (Ohio State (USA)) for its taste and texture, while Kenko preferred specially because of the pod appearance and sweetness
(Wszelaki et al., 2005). Additions to that USA consumer are willing to pay high price for non-GM vegetable soybeans that pointing the interest among consumer preference ranges. Storage facility is the most important factor for the preservation of vegetable soybean, where freezing and refrigerator are the best method to preserve it without losing sensory attributes and nutritional qualities. Blanching before cold storage is an excellent method to improve shelf- life, color, texture and protein stability
(Nair et al., 2023).
The future of vegetable soybean research in India
Vegetable soybean (edamame) cultivation in India remains limited, largely due to low consumer awareness and insufficient seed production of vegetable-type varieties, which are often susceptible to diseases. Developing new varieties with better adaptability to Indian agro-climatic conditions and improved resistance to fungal pathogens is essential. There is significant potential for edamame as a nutritious snack and as an ingredient in diverse Indian cuisines, offering considerable opportunities for the food industry. Rising health consciousness in urban areas further positions edamame as a premium, value-added product. Future research should prioritize region-specific, high-yielding varieties with enhanced quality traits such as sweetness, texture, seed size, visual appeal and resistance to insect pests
(Kim et al., 2020). Strengthening cold storage infrastructure and supply-chain systems is crucial for supporting a growing market for fresh and frozen edamame products. Additionally, promoting domestic consumption through health-focused campaigns and improving export linkages can help India tap into expanding international markets (
Global Edamame Association Market, 2021).
