The mung bean (Vigna radiata), alternatively known as the green gram, maash (٫ )٫ mūng (), monggo, đậu xanh (Vietnamese; literally, "green bean"), kacang hijau (Indonesian; literally "green bean") or munggo (Philippines), is a plant species in the legume family. The mung bean is mainly cultivated in East, Southeast and South Asia. It is used as an ingredient in both savoury and sweet dishes.
Description
The green gram is an annual vine with yellow flowers and fuzzy brown pods.
The English word mung originated from the Hindi word (), which is derived from the Sanskrit word ().
Morphology
Mung bean (Vigna radiata) is a plant species of Fabaceae which is also known as green gram. It is sometimes confused with black gram (Vigna mungo) for their similar morphology, though they are two different species. 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.
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
Germination 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 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. Once matured, it can reach up to 30 inches (76 cm) tall, with multiple branches with seed pods. Most of the seed pods become darker, while some remain green.
Nitrogen fixation and cover crop
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). 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.
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.
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 (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 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 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.