Apios Americana Medikus Research Articles

Comparison of primary and secondary metabolites and antioxidant activities by solid-state fermentation of Apios americana Medikus with different fungi

This study compared the nutritional components, isoflavones, and antioxidant activities by solid-sate fermentation of Apios americana Medikus (AAM) with seven different fungi. The total fatty acid contents increased from 120.5 mg/100 g (unfermented AAM, UFAAM) to 242.0 to 3167.5 mg/100 g (fermented AAM, FAAM) with all fungi. In particular, the values of total fatty acids were highest (26.3-fold increase) in the FAAM with Monascus purpureus. The amount of total free amino acids increased from 591.69 mg/100 g (UFAAM) to 664.38 to 1603.07 mg/100 g after fermentation except for Monascus pilosus and Lentinula edodes. The total mineral contents increased evidently after fermentation with M. purpureus, F. velutipes, and Tricholoma matsutake (347.36 → 588.29, 576.59, and 453.32 mg/100 g, respectively). The UFAAM predominated isoflavone glycosides, whereas glycoside forms were converted into aglycone forms after fermentation by fungi. The bioconversion rates of glycoside to aglycone were excellent in the FAAM with M. pilosus, M. purpureus, F. velutipes, and T. matsutake (0.01 → 0.69, 0.50, 0.27, and 0.31 mg/g, respectively). Furthermore, the total phenolic contents, total flavonoid contents, and antioxidant activities by the abovementioned FAAM were high except for L.edodes. This FAAM can be used as a potential food and pharmaceutical materials.

In vitro multiplication and phytochemical evaluation of Apios americana Medik for enhanced production of the staple food and tissues with versatile bioactivities

Apios americana Medik tissues, including tubers, flowers, leaves, and vines have both nutritional and therapeutic benefits. These tissues are extensively used in products like beverages and food supplements, driving an exponential increase in worldwide demand for the plant. However, conventional propagation of A. americana through seeds and tubers faces several challenges, including limited seed sets under manual pollination, resulting in reduced production. To overcome these challenges, micropropagation emerges as a promising solution. The current research study has developed an effective in vitro propagation strategy for A. americana using direct regeneration from apical segment explants. Full-strength Quoirin and Lepoivre (QL) medium, supplemented with vitamins and 2.0 mg/L benzylaminopurine (BAP), yielded the highest number of shoots (7.50 ± 0.06) per apical segment explant. QL medium fortified with 1.0 mg/L indole-3-butyric acid (IBA) demonstrated the highest root number (2.80 ± 0.30), length (85.80 ± 7.49 mm), and surface area (10.40 ± 0.82 cm2) in regenerated A. americana shoots. The survival rate of the regenerants in the ex vitro environment was 92.7% after acclimatization. In vitro-regenerated A. americana plants and mother plants exhibited similar ploidy level, chlorophyll content, photosynthetic rate, phytochemical composition, and antioxidant capacity, indicating similarity in their physiological and biochemical properties. This protocol offers a rapid and scalable method for generating high-quality, A. americana plant stocks with stable genome size/ploidy level, meeting the exponentially growing demand for plant tissues. Additionally, it holds potential applications in A. americana breeding and germplasm preservation.

First report of post-harvest tuber rot of Apios americana Medikus caused by Penicillium expansum in South Korea.

Apios americana Medikus, a perennial vine legume native to North America, is known as 'Indian potato' or 'Apios' for their underground tubers that are used for human consumption in Korea (Choi et al., 2017). These tubers are known to be rich in isoflavones as well as other secondary products to have known several medicinal properties (Chu et al., 2019). The harvested tubers in 2020 were observed to rot during storage of tubers for 4 months at 4°C in the genetic resource storage room at the Bioenergy Crop Research Institute, National Institute of Crop Science, Muan, Jeollanam-do, South Korea. The incidence of rot symptoms with blue mold was less than 1% per 20 kg box. Ten infected tubers were collected from several boxes and the lesions were cut into small pieces, and then surface sterilized in 1.5% NaClO for 2 minutes, followed by rinsing 3 times with sterilized water. To investigate their morphological characteristics, ten isolates were cultured in Malt Extract Agar (MEA) medium at 25° C for 5 days (Pitt and Hocking, 1988). The surface morphology of the mycelium had white or light green fluffy, and completely blue spores were formed after about 5 days. The conidia were one-stage branched with an elliptical shape, about 3.5 to 4.3 × 2.9 to 3.6 (mean 3.8 ± 0.3 × 3.2 ± 0.2) ㎛ in diameter (n=30). Genomic DNAs of the isolates were extracted using Solgent DNA Extraction Kit (Solgent, Daejeon, Korea), and then PCR products of the internal transcribed spacer (ITS1/ITS4) region and the beta-tubulin gene (Bt2a/Bt2b) were sequenced and analyzed (Glass and Donaldson, 1995). The BLASTn showed that the representative isolate had 99% homology with reference Penicillium expansum strain ICMP 2708 (ITS region and TUB2 gene) in NCBI GenBank. The sequences of the isolate were deposited in GenBank as accession numbers MZ636667 and MZ702813 for ITS and TUB2 genes, respectively. Based on the morphological characteristics and molecular analysis, the isolate was identified as P. expansum. Pathogenicity assays of the isolate were also performed using three tubers in three replicates inoculated with spore suspension (concentration, 1×106 conidia/mL) and compared with a control group inoculated with sterilized water. The inoculated Apios tubers were placed in a plastic box maintained in conditions of high humidity at 25°C. Five days after inoculation, the typical symptoms were observed on inoculated tubers, and no symptoms were observed in the control one. P. expansum was again isolated from artificially inoculated tubers to complete Koch's assumption. This is the first report of P. expansum causing tuber rot in A. americana in South Korea. As the cultivated area of Apios is increasing in Korea, it will be necessary to develop effective storage methods and management strategies for the control of storage diseases such as blue mold.

Investigation of isoflavone constituents from tuber of Apios americana Medik and its protective effect against oxidative damage on RIN-m5F cells

In our previous study, AI-3, a mixture of isoflavones, was obtained from Apios Americana Medik tuber and showed strong protective ability on oxidative damaged RIN-m5F cells. This study aimed to identify the main compounds of AI-3 and elucidate their activities and underlying mechanism. In results, eleven compounds were purified from AI-3. Among them, Compound 8 (2′-Hydroxy, 5-methoxy genistein-7-O-glucoside, HMG) was the most effective compound against H2O2-induced injury in RIN-m5F cells (stronger than positive control α-LA). Further RNA-seq analysis found that compared with H2O2 group, 388 differentially expressed genes (DEGs) were identified in HMG group. The enrichment analyses revealed fluid shear stress and atherosclerosis pathway and hepatocellular carcinoma pathway enriched the most DEGs, in which HOX-1, GST, NQO1, SQSTM, TrxR1 were significantly up-regulated. The finding indicated Keap1-Nrf2-ARE signaling pathway may play essential role in the protective effect of HMG on oxidative damaged RIN-m5F cells.

Apios americana Medikus: A novel and promising food for postpartum uterine involution

AbstractPregnancy is a prolonged and tortuous process impairing puerperal health and life, in which uterine involution playing a decisive role. However, puerperae continually suffer from postpartum complications, whereas few research has focused on the postpartum recovery and uterine involution acceleration. The requirement for a safer and efficient therapy strategy for postpartum care is very urgent. The objective of this study was to explore the effects of Apios americana Medikus tuber to be a novel adjuvant therapy strategy for postpartum recovery. As a natural resource supplement, AM possesses multiple bioactivities and high biosafety, which also more acceptable for long treatment period during and after pregnancy. AM significantly altered the levels of estrogen, progesterone and their receptors, the secretion of transforming growth factor, matrix metalloproteinases, and inflammatory cytokines. In addition, it also significantly regulated various genes related to glucose and lipid metabolism, inflammation, and cell cycle, such as PLA2G3, EGR1, LCN2, and MMP9, thereby inhibiting inflammation and facilitating postpartum recovery and uterine involution. To conclude, our results suggested that AM as a promising supplementary food or a potential adjuvant treatment to accelerate postpartum uterine involution.

Apios americana Medik flower extract protects high-glucose-treated hepatocytes and Caenorhabditis elegans

Type 2 diabetes (T2D) is a chronic metabolic disease related to glucose metabolism disorders. Increasing evidences indicate that flavonoids obtained from plants have beneficial effects on T2D. Apios americana Medik, originally cultivated in North America, is rich in flavonoids. In this study, A. americana flower extract (AFE) was purified and flavonoids were identified. The beneficial effects of AFE on glucose metabolism disorders were investigated. Results showed that AFE protected hepatic cells from oxidative stress caused by hyperglycemia and increased glucose consumption and glucose uptake. The AKT pathway was involved in AFE-mediated hypoglycemic action in LO2 cells, accompanied by phosphorylation of FoxO1, Gsk-3β and AMPK. In vivo, AFE protected Caenorhabditis elegans (C. elegans) from oxidative stress under hyperglycemia and restored the expressions of PMK-1 and SKN-1. Furthermore, AFE decreased excessive glucose and lipid accumulation and extended the lifespans of high glucose (HG) treated C. elegans. AFE might be beneficial to decrease glucose metabolism disorders and T2D.

First Report of Post-Harvest Tuber Rot of American Groundnut (Apios americana) Caused by Fusarium acuminatum.

Apios americana Medik, commonly known as American groundnut, is a leguminous perennial vine crop native to North America and is cultivated in Japan and Korea (Chu et al. 2019). Its tubers are edible and believed to be very nutritious, especially for women just after childbirth. The tubers also contain secondary metabolites, saponin and genistein, which is good for human health (Ichige et al. 2013). However, the storage of tubers at inappropriate temperatures and humidity levels can cause severe fungal infection, and adversely affect tuber quality. During March and April 2020, a white to pale-orange fungal mycelia were observed on stored American groundnut tubers, with 10 to 15% of seed tubers rotten. Infected tubers were collected, and fungal isolates were isolated on potato dextrose agar (PDA) using the single spore isolation method (Leslie and Summerell 2006). A pure culture (isolate JC20003) was obtained and stored at the Bioenergy Crop Research Institute, NICS, Muan, Republic of Korea. The fungus was cultured on PDA and V8 liquid media for 7 days at 25℃ to observe its morphological characteristics. The length and width of macroconidia ranged from 20.6 to 52.9 μm and 2.9 to 5.1 μm, respectively (n = 30). The microconidia were 8.5 to 14.9 μm and 2.3 to 4.2 μm in length and width, respectively (n = 30). Macroconidia were broadly falcate, strongly septate, 2 to 6 septations with dorsiventral curvature; chlamydospores were formed in chains; and microconidia were fusiform with 0 to 1 septation observed. Genomic DNA of the isolate was extracted using Solgent DNA extraction kit (Solgent, Daejeon, Korea), followed by PCR analysis using the internal transcribed spacer (ITS5/ITS4) and elongation factor (EF-1/EF2) genes (White et al. 1990; O'Donnel 2000). PCR products were sequenced and analyzed to confirm species identity (Yang et al. 2018). These sequences were deposited in GenBank (accession numbers MT703859/ITS and MT731939/EF). BLASTn search analysis showed 100% sequence similarity with Fusarium acuminatum (isolates N-51-1/ITS and WXWH24/EF). Based on morphological and molecular data analysis, the fungus was identified as F. acuminatum (Leslie and Summerell 2006; Marin et al. 2012). Pathogenicity tests were conducted on five tubers inoculated with 5 mm mycelial plugs with three replicates, while a non-mycelial plug served as the control. After 5 days of incubation in plastic containers at 25 °C with high humidity, typical symptoms developed. No symptoms were observed on the control tubers; F. acuminatum was re-isolated from artificially inoculated tubers to complete Koch's postulates. This is the first report on post-harvest tuber rot caused by F. acuminatum in Apios americana.

Groundnut (Apios americana Medik) Extract Enhances the Osteoblast Differentiation of MC3T3-E1 Cells

The effects of groundnut ( Apios americana Medik) extract on osteoblast differentiation were examined using MC3T3-E1 cells. MC3T3-E1 cells were treated with the crude extract along with other differentiating reagents. The alkaline phosphatase (ALP) activity of cells cultured in a differentiation medium supplemented with 0.01% crude groundnut extract was 1.5‐1.6 times higher than that of cells cultured in a differentiation medium without the extract. Crude groundnut extract was further separated into aqueous and methanol fractions. The methanol fraction enhanced ALP activity, osteocalcin, integrin-binding sialoprotein, and type I collagen expression, and calcium mineralization. Conversely, the aqueous fraction did not show such effects. Groundnut extract may enhance osteoblast differentiation, and this effect is likely conferred by water insoluble substance(s).

Apios americana Medik leaf extracts attenuate H2O2-induced hepatotoxicity

Apios americana Medik leaves are rich in polyphenols and prevent glucose-induced damage in organisms. Polyphenols are a group of natural antioxidants. Therefore, a H2O2 induced oxidative stress model of HepG2 cells was used to explore the protective effects of the Apios americana Medik leaves water extract (ALWE) against oxidative stress. Nine compounds were identified in ALWE using HPLC-TOF-MS including C18H24O13, which had not previously been reported. Fluorescence staining assays showed that the ALWE significantly decreased apoptosis, intracellular ROS generation, mitochondrial membrane potential (MMP) dissipation and mitochondrial membrane lipid peroxidation after ALWE pretreatment. Data from western blots showed that Keap1-Nrf2 and Sirt1-FoxO1 signaling pathways were involved in preventing H2O2 induced oxidative stress. Transmission electron microscope and Western blot analyses indicated that autophagy contributed to the regulation of the oxidative balance. These results together indicated that ALWE is a potential antioxidant and autophagy activator, and it protects HepG2 cells against H2O2 damage through activation of autophagy.

Nutritional and chemical profiling of UK-grown potato bean (Apios americana Medik) reveal its potential for diet biodiversification and revalorisation

Apios americana Medik, a native American plant has potential as a commercially viable Northern European-grown rootcrop, mainly due to its resistance to extreme climate and nutritional quality. Analysis of A. americana sourced from two UK sites; South (51.4690 °N, 1.1150 °W) and North (55.9661 °N, 3.2063 °W) showed that the tubers were a complete source of amino acids (UPLC-TUV analysis), were rich in protein (15.0 ± 0.0160 and 17.3 ± 0.0779%; Vario Max CN analysis), fibre (total non-starch polysaccharides, 10.4 ± 0.570 and 10.6 ± 0.280%; GC analysis) and micronutrients (calcium, manganese, iron, zinc, molybdenum, potassium and phosphorus; ICP-MS analysis). Apios americana tubers were also rich in bioactive phytochemicals. From the 156 plant metabolites measured using LC-MS/MS analysis, genistein was the major phytophenol in both the Southern- and Northern UK tubers (259 ± 12.2 mg Kg−1 and 356 ± 29.9 mg Kg−1 respectively); the peel having similar phytochemical profiles. The protein and fibre content of the leaves (17.3 ± 0.0434% and 11.7 0.0445%) and rhizomes (18.4 ± 0.0152% and 13.5 ± 0.590%) were significantly higher (p < 0.05) than the tubers. The leaves were also a good source of anthocyanins; delphinidin and cyanidin (840 ± 137 and 3934 ± 176 mg Kg−1respectively). Cultivation of A. americana as a high-protein staple-crop has enormous potential in Northern European countries for human nutrition, diet diversification, and use in livestock diets.

Physicochemical Properties of Hydroxypropylated Apios Starches.

Apios (Apios americana Medikus), also called the potato bean, Indian potato, or groundnut, belongs to the legume family, and is widely distributed across eastern North America. Apios starch was hydroxypropylated, and its physicochemical and structural characteristics were investigated in this study. The starch was extracted by alkali precipitation method, and hydroxypropylated apios starch (HPAS) was prepared using propylene oxide at concentrations of 2.5, 5, 7.5, and 10% (v/w). X-ray diffraction of native apios starch and HPAS revealed the presence of the typical ‘A’ type of cereal starch. Additionally, the hydroxypropylation affects the relative crystallinity of the starch. The swelling power and solubility of apios starch increased after hydroxypropylation. Gelatinization parameters were obtained using differential scanning calorimetry. The gelatinization temperature of native starch is 69°C, whereas that of HPAS-10% is 52.94°C. This suggests that HPAS is suitable for preparing food items requiring enhanced gelatinization.

Flavonoids from Apios americana Medikus Leaves Protect RAW264.7 Cells against Inflammation via Inhibition of MAPKs, Akt-mTOR Pathways, and Nfr2 Activation.

Apios americana Medikus was once widely accepted as staple food in India for a long time, and the tuber of which possesses high nutrients. During the past decades, most of the research has focused on the biological activity in the tubers of Apios americana Medikus whereas the leaves were ignored. In this study, the Apios americana Medikus leaf extract (ALE) was obtained and seven compounds were identified. LPS-induced RAW264.7 cells were used to study the anti-inflammation activity of ALE. As expected, ALE reduced the secretion of nitric oxide (NO) and inflammatory cytokines via inhibition of NF-κB and MAPK signaling together with activation of Nrf2-Keap1 and FOXO pathways, as well as alleviating the oxidative stress and mitochondrial dysfunction. In addition, ALE could activate HMGB1-Beclin1 and Sirt1-FoxO1 pathways and inhibit the Akt-mTOR signaling pathway to activate autophagy, protecting RAW264.7 cells from inflammation. In summary, our results suggested that ALE might help activate the anti-inflammation system, resulting in the prevention of LPS-induced damage in RAW264.7 cells.

Apios americana Medik flowers polysaccharide (AFP) alleviate Cyclophosphamide-induced immunosuppression in ICR mice

Immunosuppression refers to the suppression of the immune response. The immune function of immunocompromised people is not enough to resist bacterial, viral, fungal and other infections, leading to a series of diseases. A large number of experimental data show that polysaccharide compounds are immune modulators, which can enhance the body immunity with little toxic. Meanwhile, it can reduce the side effects of commonly used immunosuppressants, such as cytotoxicity, decreased ability of the body to fight infection, and inhibition of the reproduction of bone marrow hematopoietic cells. It can be used as oral or injectable drugs. In this study, a purified polysaccharide was primarily extracted from the flowers of Apios americana Medik (AAM), which can improve the immunosuppression induced by cyclophosphamide (CTX). The immunoenhancement effect of AFP was evaluated by measuring the body weight, immune organ index, cytokine secretion and antibody generated levels of CTX-induced mice. Our results showed that AFP could significantly improve the above immune indexes, which indicated AFP could alleviate immunosuppression induced by CTX. The study provided a theoretical basis for the promotion, development and application of AAM as a newly introduced food material.

Apios americana Medikus tuber polysaccharide exerts anti-inflammatory effects by activating autophagy.

The tubers of Apios americana Medikus possess high nutritional value and have been used as food in many countries for a long time. However, few researches have focused on the tuber polysaccharides. In the present study, a purified polysaccharide (ATP-1) was isolated with the average molecular weights of 12.16 kDa. ATP-1 significantly suppressed the release of nitric oxide (NO) and inflammatory cytokines from LPS-induced RAW 264.7 cells, as well as oxidative stress and mitochondrial dysfunction. Meanwhile, ATP-1 reduced oxidative damage via the NF-κB, MAPKs and Nrf2-Keap1 signaling pathways in RAW264.7 macrophages. Furthermore, autophagy was activated by HMGB1-Beclin1, Sirt1-FoxO1 and Akt-mTOR signaling pathways, leading to a relief of oxidative stress, mitochondrial dysfunction, inflammation and an expression enhancement of autophagy-related proteins, such as LC3, Beclin1, Atg4, Atg5, and Atg7. In summary, our results suggested that ATP-1 might help to activate the anti-inflammation system，resulting in prevention of LPS-induced damage in RAW264.7 cells.

Apios americana Medik flowers extract protects PC12 cells against H2O2 induced neurotoxicity via regulating autophagy

Since flavonoids are antioxidant compounds, they could beneficially affect neurodegenerative diseases where reactive oxygen species are involved. In this study, we firstly isolated and identified fourteen compounds from the flowers of Apios americana Medik. Then, we tested whether Apios americana Medik flowers water extract (AFWE) exerts a protective effect on H2O2 induced PC12 cells injure. As expected, pretreatment with AFWE inhibited cytotoxicity and DNA condensation in H2O2induced PC12 cells. Exposure of PC12 cells to H2O2 resulted in reactive oxygen species accumulation and mitochondrial dysfunction, while AFWE alleviated these damages. AFWE obviously reversed the alternations as H2O2 increased Caspase-3 and decreased the ratio of Bcl-2/Bax expressions. Furthermore, autophagy in PC12 cells was further activated by AFWE, which was beneficial to resisting adversity. These results manifest that AFWE prevents H2O2 induced damage via regulating autophagy.

Apios americana Medik flowers polysaccharide (AFP-2) attenuates H2O2 induced neurotoxicity in PC12 cells

Oxidative stress is a critical cause for the progression of neurodegenerative diseases, indicating that screening natural antioxidant and pharmacological targeting of mechanism need more attention. Natural plant polysaccharides are the primary group of natural antioxidants showing mighty antioxidant activity. Therefore, a polysaccharide (AFP-2) from flowers of Apios americana Medik was isolated, purified and characterized. Then, a H2O2-induced PC12 cells oxidative stress model was established to investigate the neuroprotective role of AFP-2 and to clarify the potential mechanism of action against H2O2-induced neurotoxicity. It was found that AFP-2 reduced ROS production and mitochondrial damage caused by hydrogen peroxide in PC12 cells. In addition, data from transmission electron microscope and western blot displayed that AFP-2 significantly activated autophagy in PC12 cells via Akt-mTOR pathway. These results together qualify AFP-2 as an interesting natural polysaccharide worth further investigation as a neuroprotective agent.

Antioxidant Activities and Quality Characteristics of Noodle with Added Apios (Apios americana Medikus) Cultivated in Korea

Antioxidant Activities and Quality Characteristics of Noodle with Added Apios (Apios americana Medikus) Cultivated in Korea

Biological activities of unique isoflavones prepared from Apios americana Medik.

Four unique isoflavone aglycones (barpisoflavone A (1), 2'-hydroxygenistein (2), 5-methylgenistein (3), and gerontoisoflavone A (4)) whose structures were related to genistein were prepared from the tuber of Apios americana Medik. We examined the estrogen receptor and androgen receptor binding activities, estrogen agonistic activities, antioxidant activities, and α-glucosidase inhibitory activities of 1-4. The results obtained showed that 2 possessed potent and 1, 3, and 4 possessed moderate estrogen partial agonistic activities, 1 and 2 possessed moderate antioxidant activities, and 2 and 3 possessed moderate α-glucosidase inhibitory activities.

Apios americana Medik Extract Alleviates Lung Inflammation in Influenza Virus H1N1- and Endotoxin-Induced Acute Lung Injury.

Apios americana Medik (hereinafter Apios) has been reported to treat diseases, including cancer, hypertension, obesity, and diabetes. The therapeutic effect of Apios is likely to be associated with its anti-inflammatory activity. This study was conducted to evaluate the protective effects of Apios in animal models of acute lung injury induced by lipopolysaccharide (LPS) or pandemic H1N1 2009 influenza A virus (H1N1). Mice were exposed to LPS or H1N1 for 2-4 days to induce acute lung injury. The treatment groups were administered Apios extracts via oral injection for 8 weeks before LPS treatment or H1N1 infection. To investigate the effects of Apios, we assessed the mice for in vivo effects of Apios on immune cell infiltration and the level of pro-inflammatory cytokines in the bronchoalveolar lavage (BAL) fluid, and histopathological changes in the lung. After induction of acute lung injury, the numbers of neutrophils and total cells were lower in the Apios-treated groups than in the non-Apios-treated LPS and H1N1 groups. The Apios groups tended to have lower levels of tumor necrosis factor-a and interleukin-6 in BAL fluid. In addition, the histopathological changes in the lungs were markedly reduced in the Apios-treated groups. These data suggest that Apios treatment reduces LPS- and H1N1-induced lung inflammation. These protective effects of Apios suggest that it may have therapeutic potential in acute lung injury.

Evaluation of Phenotypic Variation in a Collection of Apios americana: An Edible Tuberous Legume

ABSTRACTApios (Apios americana Medik.), sometimes called “potato bean,” is a nitrogen‐fixing legume, native to eastern North America, that produces protein‐rich tubers at nodes along belowground stolons. Apios was used as a staple food source by Native Americans throughout eastern North America and holds promise as a crop. An Apios breeding program conducted during 1985 to 1994 involved the collection of ∼210 wild accessions, followed by hybridization and selection, with assessments of &gt;2200 lines. Of these, 53 genotypes were retained for further evaluation. The study reports the phenotypic variation in this collection, at three locations and under three growing conditions (field, pots, and grow‐bags). We found significant (P &lt; 0.05) variation among the genotypes for 18 of the 20 measured traits under field conditions, and for seven of 20 traits in pots and grow‐bags. Internode length, plant vigor, and stem diameter at 2 and 5 mo had strong correlations (r &gt; 0.56, P &lt; 0.01) with belowground yield plant−1. Four phenotypically distinct clusters of genotypes were evident in the Apios collection. Several genotypes produced high yields in all locations—up to 1515 g of belowground tuber yield plant−1. The superior germplasm identified in this project may be suitable as cultivars, and will aid in further development of Apios lines as a crop.