Mung bean

Mung bean (Vigna radiata) is a plant species of Fabaceae which is also known as green gram.[7] It is sometimes confused with black gram (Vigna mungo) for their similar morphology, though they are two different species.[8] The green gram is an annual vine with yellow flowers and fuzzy brown pods. There are three subgroups of Vigna radiata, including one cultivated (Vigna radiata subsp. radiata) and two wild ones (Vigna radiata subsp. Sublobata and Vigna radiata subsp. glabra). It has a height of about 15–125 cm.[9] Mung bean has a well-developed root system. The lateral roots are many and slender, with root nodules grown.[10] Stems are much branched, sometimes twining at the tips. Young stems are purple or green, and mature stems are grayish yellow or brown. They can be divided into erect cespitose, semi-trailing and trailing types.[10] Wild types tend to be prostrate while cultivated types are more erect.[9] Leaves are ovoid or broad-ovoid, cotyledons die after emergence, and ternate leaves are produced on two single leaves. The leaves are 6–12 cm long and 5–10 cm wide. Racemes with yellow flowers are borne in the axils and tips of the leaves, with 10-25 flowers per pedicel, self-pollinated. The fruits are elongated cylindrical or flat cylindrical pods, usually 30-50 per plant. The pods are 5–10 cm long and 0.4-0.6 cm wide and contain 12-14 septum-separated seeds, which are either green, yellow, brown or blue and can be cylindrical or spherical in shape.[10] Seed colors and presence or absence of a rough layer are used to distinguish different types of mung bean.[9]

Typically within 4–5 days, but the actual rate of germination varies according to the amount of moisture introduced during the germination stage.[11] Epigeal with the stem and cotyledons emerging from the seedbed.[12]

The seed splits, and a soft, whitish root grows. Mung bean sprouts are harvested during this stage. If not harvested, it develops a root system, then a green stem which contains two leaves shoots up from the soil. After that, seed pods begin to form on its branches, with 10-15 seeds contained in each pod.[11]

The maturation can take up to 60 days. Once matured, it can reach up to 30 inches tall, with multiple branches with seed pods. Most of the seed pods become darker, while some remain green.[11]

Mung beans are recognized for their high nutritive value. Mung beans contain about 55%-65% carbohydrate (equal to 630 g/kg dry weight) and are rich in protein, fat, vitamins and minerals.[13] It is composed of about 20%-50% protein of total dry weight, among which globulin (60%) and albumin (25%) are the primary storage proteins (see table). Mung bean is considered to be a substantive source of dietary proteins. The proteolytic cleavage of these proteins are even higher during sprouting. Mung bean carbohydrates are easily digestible, which causes less flatulence in humans compared to other forms of legumes. Both seeds and sprouts of mung bean produce lower calories compared to other cereals, which makes it more attractive to obese and diabetic individuals.[7]

As a legume plant, mung bean is in symbiotic association with Rhizobia which enables it to fix atmospheric nitrogen (58–109 kg per ha mung bean). It can provide large amounts of biomass (7.16 t biomass/ha) and Nitrogen to the soil (ranging from 30 to 251 kg/ha).[8] The nitrogen fixation ability not only enables it to meet its own nitrogen requirement, but also benefit the succeeding crops. It can be used as a cover crop before or after cereal crops in rotation, which makes a good green manure.[8]

Mung bean is a warm season and frost-intolerant plant. Mung bean is suitable for being planted in temperate, sub-tropical and tropical regions. The most suitable temperature for mung bean's germination and growth is 15-18 °C. Mung bean has high adaptability to various soil types, while the best pH of the soil is between 6.2 and 7.2. Mung bean is a short-day plant and long days will delay its flowering and podding.[15][16]

The seedbed for mung bean is similar to other legume plants. Mung beans can be usually interplanted with maize, sorghum and others. Sowing mung beans should follow rotation cropping in case of being infected by pathogens. Before sowing, the seedbed should be ploughed and tilled thoroughly by adding enough organic fertilizer. Also, inoculating proper Rhizobium before seeding is also recommended for the first-time planting. The seed should be planted 4–8 cm deep, which is depending on the soil type. The density for seeding should be 150,000-200,000 plants per acre with a 50–80 cm row spacing. The seeding density should be different to distinct conditions. The early-maturing, upright type mung bean planted in non-rich soil with early seeding time should have a higher density than the late-maturing varieties, vine/half-vine type ones planted in rich soil with late seeding time.[15]

The mung bean varieties now are mainly targeted in resistance to pests and diseases, particularly the mung bean weevil and mung bean yellow mosaic virus (MYMV). For now, the main varieties include Samrat, IPM2-3, SML 668 and Meha in India; Crystal, Jade-AU, Celera-AU，Satin II，Regur in Australia; Zhonglv No.1, Zhonglv No.2, Jilv No.2, Jilv No.7, Weilv No.4, Jihong 9218, Jihong 8937, Bao 876-16, Bao 8824-17 in China. Also, with the help of the World Vegetable Centre, the traits of mung bean have been improved a lot.[17][18][19][20]

The requirements of chemical elements for mung bean is quite similar to other legume plants. The needs for different elements of soybean can be a reference for mung bean. During the management period, the slightly acid soil is perfect for mung bean's growth, so adding proper lime to the soil is the best way to adjust the pH. And it is best to lime the year before planting mung bean.[15]

Weeding should be implemented 1) before seeding; 2) after the occurrence of the first and second compound leaf 3) the branch period. There is a mechanical and chemical method for weed control for mung bean. Before planting, there should be a thorough weeding by using rotary hoeing. Also, wider spacing is better for weed control if it's the first time planting mung bean. For the chemical ones, the Dual (metolachlor) and Treflan (trifluralin) are efficient for mung bean as the preplant use. However, later emerging weeds are difficult to control since the herbicides will also harm mung bean and mung bean is not as resistant to weeds as soybean. Besides, the labelled herbicides for mung bean are few. For these reasons, weed control is always the main problem for mung bean weeding.

Mung bean is sensitive to water. The requirements for water are varied from the different growth periods of mung bean. It is good to keep a slightly dry soil for the very beginning growth of mung bean, while the flowering and podding period mung bean need much water. Moreover, it is always essential to avoid drought or waterlogging for the soil.

The yield potential of mung bean is around 2.5 to 3.0 t/ha, however, usually due to the resistance to environmental stress and improper management, the average productivity for mung bean is only 0.5 t/ha. Since the indeterminate flowering habit of mung bean, when facing the proper environmental conditions, there can be both flowers and pods in one mung bean plant, which make it difficult for harvesting mung bean. The perfect harvesting stage is when 90% of pods' colour in one yield has been black. Mung bean can use a harverster for harvesting. It is important to set up the header in case of over-threshing.[21][22]

The perfect moisture of grain for transportation is 13%. Before storage, the cleaning and grading process must be done. The ideal storage condition should keep the mung bean's moisture at exactly 12%.[21][22]

Insect pests attack mung bean at all crop stages from sowing to storage stage and take a heavy toll on crop yield. Some insect pests directly damage the crop, while others act as vectors of diseases to transmit the virus.

Stem fly (bean fly), is one of the major pests of mung bean.[24] This pest infests the crop within a week after germination and under epidemic conditions, it can cause total crop loss.[25]

Whitefly, B. tabaci is a serious pest in mung bean and damages the crop either directly by feeding on phloem sap and excreting honeydew on the plant that forms black sooty mould or indirectly by transmitting Mung bean yellow mosaic disease (MYMD). Whitefly causes yield losses between 17% and 71% in mung bean.

Thrips infest mung bean both in the seedling and in flowering stages. During the seedling stage, thrips infest the seedling's growing point when it emerges from the ground, and under severe infestation, the seedlings fail to grow. Flowering thrips cause heavy damage and attack during flowering and pod formation, which feed on the pedicles and stigma of flowers. Under severe infestation, flowers drop and no pod formation takes place.[23]

Spotted pod borer, Maruca vitrata (Fab.) is a major insect pest in mung bean in the tropics and subtropics.[26] The pest causes a yield loss of 2–84% in mung bean amounting the US $30 million. The larvae damage all the stages of the crop including flowers, stems, peduncles, and pods; however, heavy damage occurs at the flowering stage where the larvae form webs combining flowers and leaves.

Cowpea aphid sucks plant sap that causes loss of plant vigor and may lead to yellowing, stunting or distortion of plant parts. Further, aphids secrete honeydew (unused sap) which leads to the development of sooty mould on plant parts. Cowpea aphid also can act as a vector of the mung bean common mosaic virus.

Bruchid is the most severe stored pests of legume seeds worldwide, damage up to 100% losses within 3–6 months, if not controlled.[27] Bruchid infestation in mungbean results in weight loss, low germination, and nutritional changes in seeds, thereby reducing the nutritional and market value, rendering it unfit for human consumption, agricultural and commercial uses.[24]

Viral, bacterial, and fungal diseases are of economic importance in South Asia, South East Asia, and Sub-Saharan Africa.

Mungbean yellow mosaic disease (MYMD) is an important viral disease of mung bean,[28][24] which causes severe yield losses annually. MYMD is caused by three distinct begomoviruses, transmitted by whitefly Bemisia tabaci.[23] The economic losses due to MYMD account for up to 85% yield reduction in India.[29]

The major fungal diseases are Cercospora leaf spot (CLS), dry root rot, powdery mildew and anthracnose.

Dry root rot [Macrophomina phaseolina (Tassi) Goid] is an emerging disease of mungbean, causing 10–44% yield losses in mung bean production in India and Pakistan.[30][24] The pathogen affects the fibrovascular system of the roots and basal internodes of its host, impeding the transport of water and nutrients to the upper parts of the plant.[31]

Halo blight, bacterial leaf spot, and tan spot are important bacterial diseases.

Abiotic stresses negatively influence plant growth and productivity and are the primary causes of extensive agricultural losses worldwide. Reduction in crop yield due to environmental variations has increased steadily over the decades. Abiotic stresses include extreme events and factors related to the atmosphere (heat, cold, and frost); water (drought and flooding); radiation (UV and ionizing radiation); soil (salinity, mineral or nutrient deficiency, heavy metal pollutants, pesticide residue, etc.) and mechanical factors (wind, soil compaction).[23]

Salinity affects crop growth and yield by the way of osmotic stress, ion toxicity, and reduced nodulation which ultimately lead to reduced nitrogen-fixing ability.[32] Excessive salt led to leaf injury, and then reduced photosynthesis.[33]

High-temperature stress negatively affects reproductive development in mung bean and affects all reproductive traits like flower initiation, pollen viability, fertilization, pod set, seed quality, etc.[34] High Temperature over 42 °C during summer causes hardening of seeds due to incomplete sink development.[35]

Mung bean requires a light moisture regime in the soil during its growing period, while at the time of harvest complete dry conditions are required. Since it is mostly grown under rainfed conditions, it is more susceptible to water deficiencies as compared to many other food legumes.[36] Drought affects its growth and development by negatively affecting vegetative growth, flower initiation, abnormal pollen behavior and pod set. However, simultaneously, excess moisture or waterlogging, even for a short period of time, especially at the early vegetative stage may be detrimental to the crop.[37]

Mung bean may also be affected by excess soil and atmospheric moisture during the rainy season which may lead to pre-harvest sprouting in mature pods.[24] It deteriorates the quality of the seed/grain produced.

Using climate analysis tools delivered on the web can firstly help farmers to interrogate climate records to ask questions relating to rainfall, temperature, radiation, and derived variables to avoid some of the abiotic stresses. Deployment of varieties with genetic resistance is the most effective and durable method for integrated disease management, in the mean time focusing on yield, height, grain quality, market opportunities and seed availability.[23] For pre-harvest sprouting (PHS), the development of mung bean cultivars with short (10–15 days) period of fresh seed dormancy (FSD) is important to curtail losses incurred by PHS.[38]

Whole cooked mung beans are generally prepared from dried beans by boiling until they are soft. Mung beans are light yellow in colour when their skins are removed.[3] Mung bean paste can be made by hulling, cooking, and pulverizing the beans to a dry paste.[3]

Although whole mung beans are also occasionally used in Indian cuisine, beans without skins are more commonly used. In Karnataka, Maharashtra, Gujarat, Kerala and Tamil Nadu, whole mung beans (called pachai payaru (பச்சை பயறு) in Tamil, cherupayar (ചെറുപയർ) in Malayalam, pesalu (పెసలు) in Telugu and hesaru kaalu (ಹೆಸರು ಕಾಳು) in Kannada) are commonly boiled to make a dry preparation often served with rice gruel (kanji கஞ்சி). It is called mūṅg (मूँग) in Hindi, and mug (মুগ) in Bengali. In Sri Lanka, it is called mun (මුං) in Sinhala. In Odia, it is called muga ḍāli (ମୁଗ ଡାଲି). Hulled mung beans can also be used in a similar fashion as whole beans for the purpose of making sweet soups.

'Summer Moong' is a short duration mung bean pulse crop grown in northern India. Due to its short duration, it can fit well inbetween of many cropping systems. It is mainly cultivated in East and Southeast Asia and the Indian subcontinent. It is considered to be the hardiest of all pulse crops and requires a hot climate for germination and growth.

Mung beans in some regional cuisines of India are stripped of their outer coats to make mung dal. In Bangladesh and West Bengal the stripped and split bean is used to make a soup-like dal known as moog dal (মুগ ডাল).

In the South Indian states of Karnataka, Tamil Nadu, Telangana and Andhra Pradesh, and also in Maharashtra, steamed whole beans are seasoned with spices and fresh grated coconut in a preparation called "pesalu" పెసలు in Telugu or usuli or guggari in Kannada or sundal சுண்டல் in Tamil or "usal" उसळ in Marathi. In South India, especially Andhra Pradesh, batter made from ground whole moong beans (including skin) is used to make a variety of dosa called pesarattu or pesara dosa. The same is called Adai Dosai in Tamil Nadu and ade dose in Karnataka.

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  Green gram dal
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  Indian mung dal
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  Mung bean dessert
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  Mung-bean fry
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  Mung pakon, traditional Bengali pitha, Bangladesh.

In southern Chinese cuisine, whole mung beans are used to make a tángshuǐ, or dessert, otherwise literally translated 'sugar water', called lǜdòu tángshuǐ, which is served either warm or chilled. They are also often cooked with rice to make congee. Unlike in South Asia, whole mung beans seldom appear in savory dishes.

In Hong Kong, hulled mung beans and mung bean paste are made into ice cream or frozen ice pops.[3] Mung bean paste is used as a common filling for Chinese mooncakes in East China and Taiwan.[3] During the Dragon Boat Festival, the boiled and shelled beans are used as filling in zongzi 粽子 glutinous rice dumplings prepared for consumption.[3] The beans may also be cooked until soft, blended into a liquid, sweetened, and served as a beverage, popular in many parts of China. In south China and Vietnam, mung bean paste may be mixed with sugar, fat, and fruits or spices to make pastries, such as Bánh đậu xanh.

In Korea, skinned mung beans are soaked and ground with some water to make a thick batter. This is used as a basis for the Korean pancakes called bindae-tteok ({녹두}빈대떡).

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  Korean mung bean pancakes (Korean: 빈대떡) being cooked
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  Chinese mung bean soup from Hong Kong

In the Philippines, ginisáng monggó/mónggo (sautéed mung bean stew), also known as monggó/mónggo guisado or balatong, is a savoury stew of whole mung beans with prawns or fish. It is traditionally served on Fridays of Lent, when the majority of Catholic Filipinos traditionally abstain from meat. Variants of ginisáng monggó/mónggo may also be made with chicken or pork.[44][45][46] Mung beans are also used in the Filipino dessert ginataang munggo (also known as balatong), a rice gruel with coconut milk and sugar flavored with pandan leaves or vanilla.[47][48]

Mung bean paste is also a common filling of pastries known as bakpia in Indonesia and hopia the Philippines, and further afield in Guyana (where it is known as "black eye cake"). It is also used as a filling for pan de monggo, a Filipino bread.[49] In Indonesia, mung beans are also made into a popular dessert snack called es kacang hijau, which has the consistency of a porridge. The beans are cooked with sugar, coconut milk, and a little ginger.

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  Filipino ginisang monggo with ampalaya and shrimp
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  Filipino ginataang munggo, a sweet rice gruel with mung beans and coconut milk, sugar, and pandan leaf extract
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  Filipino hopia filled with mung bean paste
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  Indonesian bubur kacang hijau, made with mung beans in coconut milk and sugar

A staple diet in some parts of the Middle East is mung beans and rice. Both are cooked together in a pilaf-like rice dish called maash wa ruzz, which means mung beans and rice.

These sprouts have been transferred from a similarly-shaped colander in which they had been grown with moisture. They are ready to be cooked.

Mung beans are germinated by leaving them in water for four hours of daytime light and spending the rest of the day in the dark. Mung bean sprouts can be grown under artificial light for four hours over the period of a week. They are usually simply called "bean sprouts". However, when bean sprouts are called for in recipes, it generally refers to mung bean or soybean sprouts.

Mung bean sprouts are stir-fried as a Chinese vegetable accompaniment to a meal, usually with garlic, ginger, spring onions, or pieces of salted dried fish to add flavour. Uncooked bean sprouts are used in filling for Vietnamese spring rolls, as well as a garnish for phở. They are a major ingredient in a variety of Malaysian and Peranakan cuisine, including char kway teow, hokkien mee, mee rebus, and pasembor.

In Korea, slightly cooked mung bean sprouts, called sukjunamul (Korean: 숙주나물), are often served as a side dish. They are blanched (placed into boiling water for less than a minute), immediately cooled in cold water, and mixed with sesame oil, garlic, salt, and often other ingredients.

In the Philippines, mung bean sprouts are called togue and are most commonly used in lumpia rolls called lumpiang togue.[50][51]

In India, mung bean sprouts are cooked with green chili, garlic, and other spices.

In Indonesia the food are often used as fillings like tahu isi (stuffed tofu) and complementary ingredient in many dishes such as rawon and soto.

In Japan, the sprouts are called moyashi.

Sichuan-style spicy liangfen

Mung bean starch, which is extracted from ground mung beans, is used to make transparent cellophane noodles (also known as bean thread noodles, bean threads, glass noodles, fensi (粉絲), tung hoon (冬粉), miến, bún tàu, or bún tào). Cellophane noodles become soft and slippery when they are soaked in hot water. A variation of cellophane noodles, called mung bean sheets or green bean sheets, are also available.

In Korea, a jelly called nokdumuk (Korean: 녹두묵; also called cheongpomuk; 청포묵) is made from mung bean starch; a similar jelly, colored yellow with the addition of gardenia coloring, is called hwangpomuk (황포묵).

In northern China, mung bean jelly is called liangfen (Chinese: 涼粉; lit. 'chilled bean jelly'), which is a very popular food during summer. The Hokkiens add sugar to mung bean jelly to make it a dessert called Lio̍k-tāu hún-kóe (Chinese: 綠豆粉粿; lit. 'mung bean flour cake').

Mung batter is used to make crepes named pesarattu in Andhra Pradesh, India and pancakes named bindaetteok in Korea. (The starch content is around 56.82%.)

Mung beans are increasingly used in plant-based meat and egg alternatives such as Beyond Meat and Eat Just's Just Egg.[52]