Mung bean
The mung bean or green gram is a plant species in the legume family. It is mainly cultivated in East, Southeast, and South Asia and used as an ingredient in both savoury and sweet dishes.
Names
The English names "mung" or "mungo" originated from the Hindi word , which is derived from the Sanskrit word . It is also known in Philippine English as "mongo bean". Other less common English names include "golden gram" and "Jerusalem pea".Description
The green gram is an annual vine with yellow flowers and fuzzy brown pods. It has a height of about.Mung bean has a well-developed root system. The lateral roots are many and slender, with root nodules grown. 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. Wild types tend to be prostrate while cultivated types are more erect.
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 can be either cylindrical or spherical in shape, and green, yellow, brown, or blue in color. Seed colors and presence or absence of a rough layer are used to distinguish different types of mung bean.
Growth stages
is typically within 4–5 days, but the actual rate varies according to the amount of moisture introduced during the germination stage. It is epigeal, with the stem and cotyledons emerging from the seedbed.After germination, 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 and shoots up from the soil. After that, seed pods begin to form on its branches, with 10–15 seeds contained in each pod.
The maturation can take up to 60 days. It can reach up to 76 cm tall, with multiple branches with seed pods. Most of the seed pods become darker, while some remain green.
Similar species
Vigna radiata is sometimes confused with Vigna mungo due to their similar morphology.Taxonomy
Mung beans are one of many species moved from the genus Phaseolus to Vigna in the 1970s. The previous names were Phaseolus aureus or P. radiatus.It is a species of Fabaceae and is also known as green gram.
There are three subgroups, including one cultivated and two wild ones.
Ecology
Nitrogen fixation and cover crop
As a legume plant, mung bean is in symbiotic association with Rhizobia, which enables it to fix atmospheric nitrogen. It can provide large amounts of biomass and nitrogen to the soil. The nitrogen fixation ability not only enables it to meet its own nitrogen requirement, but also benefits the succeeding crops. It can be used as a cover crop before or after cereal crops in rotation, which makes a good green manure.Domestication
The mung bean was domesticated in India, where its progenitor occurs wild.2nd millennium BCE scripture Yajurveda in its 4th chapter refers to mudga as one of the important grains and asks Rudra to bless with its good harvest in Rudradhyaya. The mung bean is listed as one of the nine auspicious grains in Vedic astrology and associated with planet Budha.
Carbonized mung beans have been discovered in many archeological sites in India. Areas with early finds include the eastern zone of the Harappan civilisation in modern-day Pakistan and western and northwestern India, where finds date back about 4,500 years, and South India in the modern state of Karnataka where finds date back more than 4,000 years. Some scholars, therefore, infer two separate domestications in the northwest and south of India. On the other hand, a recent study suggested a single genetic origin likely contributing to the loss of pod shattering, the key domestication trait in legumes. In South India, there is evidence for the evolution of larger-seeded mung beans 3,500 to 3,000 years ago. By about 3,500 years ago mung beans were widely cultivated throughout India.
Cultivated mung beans later spread from India to China and Southeast Asia. Archaeobotanical research at the site of Khao Sam Kaeo in southern Thailand indicates that mung beans had arrived in Thailand by at least 2,200 years ago.
A genetic study demonstrated that, following its domestication in South Asia, mung bean spread sequentially to Southeast Asia and East Asia and eventually to Central Asia, despite the geographic proximity of South and Central Asia. The study suggests that the short and dry growing seasons in the northern regions of Asia were not suitable for southern cultivars, which had been bred for extended life cycles to maximize yield. This highlights the critical role of ecological factors, such as climate, in shaping crops evolution.
Cultivation
Varieties
The mung bean varieties now are mainly targeted in resistance to pests and diseases, particularly the bean weevil and mung bean yellow mosaic virus. 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 Center, the traits of mung bean have been considerably improved.'Summer Moong' is a short-duration mung bean pulse crop grown in northern India. Due to its short duration, it can fit well in-between 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.
Climate and soil requirements
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. 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.Harvest
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. Due to the indeterminate flowering habit of mung bean, when facing proper environmental conditions, there can be both flowers and pods in one mung bean plant, which makes it difficult to harvest it. The perfect harvesting stage is when 90% of the pods' colour in one yield has been black. Mung beans can use a harvester for harvesting. It is important to set up the header in case of over-threshing.Transportation and storage condition
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%.Pests, diseases and abiotic stress
Most of the mung bean cultivars have a yield potential of 1.8–2.5 tons/ha. However, the actual average productivity of mung bean hovers around 0.5–0.7 t/ha. Several factors constrain its yield, including biotic stresses and abiotic stresses. Stresses not only decrease productivity but also affect the physical quality of seeds, making them unusable or unfit for human consumption. All the stresses collectively can lead to significant yield losses of up to 10–100%.Pests
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 is one of the major pests of mung bean. This pest infests the crop within a week after germination and under epidemic conditions, it can cause total crop loss.
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. Whitefly causes yield losses between 17% and 71% in mung bean.
Thrips infest mung bean both in the seedling and 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.
Spotted pod borer, Maruca vitrata, is a major insect pest in mung bean in the tropics and subtropics. The pest causes a yield loss of 2–84% in mung bean amounting to 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 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 pest of legume seeds worldwide, with damage up to 100% losses within 3–6 months, if not controlled. 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, and agricultural and commercial uses.