Dr Siddra Ijaz - Mung bean crop is cultivated in a diverse range of environmental conditions and has well adaptability to resource deficit areas of Asia and Africa where it is a valuable asset of poor farmers. Mung bean is a popular crop of South East Asia and due to its short life cycle of 70-80 days, it can easily be fit in different cropping patterns. Some varieties can mature as earlier as 60-65 days and can be adjusted very easily between two exhaustive crops to improve soil health.
Like other leguminous crops, a specific feature of mung bean is ability to fix atmospheric nitrogen to biologically important nitrogenous compounds with the help of certain bacteria. Such crops not only fulfill their own nitrogen requirement but also leave enough amount of nitrogen for the coming crops thus lessening dependency on chemical fertilisers which are costly and believed to be a source of certain pollutions in case of excessive use. Due to this unique ability, it is advised to adjust mung bean in different cropping pattern or co-cultivate it with other crops to sustain soil fertility.
Mung bean, like other pulses, has high nutritional value for human. It contains 22 percent protein and thus is very important source of protein for vegetarians and those unable to depend on animal source of protein due to clinical reasons. Presence of antioxidants in it helps in curing cancer. It strengthens the immune system of human body that helps in fighting against bacterial and viral infections. It also has an exceptional amino acid profile and is rich in certain amino acids like lysine which are deficit in cereals like wheat, rice, barley and oat. Mung bean is a rich source of folate, magnese, magnesium, zinc, calcium, vitamin B1, vitamin B5 and vitamin B6.
The significant role in improving mung bean statistics was played by modern mung bean varieties. The old varieties were of trailing plant type that flower in specific day length and were rendered as photoperiod sensitive. They had indeterminate growth habit and continue fruiting for a longer period resulting in simultaneous presence of mature pods, green pods of different age and flowers. Therefore, it was not possible to harvest the crop at once and the only choice was manual picking of mature pods at regular intervals causing high labor charges. These varieties were also low yielding and could only be grown in traditional kharif season as a sole crop. But gradual genetic improvement brought series of mung bean varieties which gained popularity in major mung bean growing area and revolutionised mung bean production.
Characteristic features of new varieties are insensitivity to day length, erect plant type, earlier and uniform maturity, semi determinate growth habit, better tolerance to diseases along with higher yield potential. Additionally, these varieties have bold sized grains with shiny green color hence, were attractive for buyers and fetched higher prices in the market. These varieties changed the mung bean culture and mung bean spring planting was started due to day length insensitivity of these varieties. Erect plant type and uniform maturity mechanised mung bean field operations like sowing, hoeing and harvesting. Higher yields and good prices in the market make it popular among the farmers. It can easily fit in between a wheat and succeeding rice crop and intercropped successfully in sugarcane and cotton. Now, it is the only pulse crop in Pakistan which is capable of fulfilling its domestic demand.
However, climate change resulting in unpredictable rain patterns, emergence of new disease races, flourishing insect pest complex having pesticide resistance posed serious threats to this crop. Efforts are being made with the collaboration of various national and international institutes to find solutions of these problems and making the crop safer to improve earning of farmers. Application of modern biotechnological procedures in mung bean breeding can further improve the genetic makeup, morphological architecture and physiology of mung bean plant to make it more climate resilient crop.
Mung bean Yellow Mosaic Diseases (MYMD) is the major threat to mung bean production and inflicts heavy yields losses annually. This disease is caused by Mung bean Yellow Mosaic virus, whose carrier is whitefly and is transmitted through it from infested to healthy plant. Initially the disease appears as small yellow spots along the veins on young leaves and then spread over the leaves. Under severe infection, the characteristic symptoms include yellowing or chlorosis of entire leaf on whole plant followed by necrosis, shortening of internodes, severe stunting of plants with no yield or few flowers and deformed pods producing small, immature, and shriveled seeds. This disease causes severe yield losses in mungbean which may exceed up to 85 percent. The disease also affects other leguminous crops like Mash, Mothbean and Soybean. The disease occurs over a wide range of climatic conditions in summer and the resistance against this disease is found to be scarce in mungbean germplasm.
Development of disease resistant genotypes appeared to be the best strategy of controlling this disease. Many MYMD resistant varieties like 6601, 121-25, NM51, NM54, NM92, AZRI-06, NM11, NM16 etc have been released in the past but they lost resistance after a certain time period due to evolutionary changes in virus resulting in new virulent races. Therefore, there is a dire need to understand the genetic basis of resistance in mung bean to devise an efficient breeding program leading to the continuous development of resistant varieties for replacement of old stock.
Molecular biology has provided an opportunity for exploring the genetic mechanism of MYMV resistance in mung bean. Some DNA markers have been identified that are linked to resistant genes in mung bean, mash bean, adzuki bean etc. Efforts are being made through the collaboration of University of Agriculture Faisalabad, Ayub Agricultural Research Institute, Faisalabad, and Nuclear Institute for Agriculture and Biology Faisalabad for the development of high yielding and MYMD resistant breeding material through integration of conventional and molecular marker assisted breeding approaches.