Yellow Mosaic Disease (YMD) is a severe viral disease that affects green gram (Vigna radiata), an essential legume crop cultivated in tropical and subtropical regions of the globe. The disease is caused by a single-stranded DNA virus called Mungbean yellow mosaic India virus (MYMIV), transmitted by persistent, circulative whiteflies (Bemisia tabaci). The virus infects the plant’s phloem tissue, causing yellow mosaic symptoms on the foliage, stunted growth, and decreased yield. The disease can yield up to 100 percent losses, particularly if it infects seedlings.
The first reported case of YMD occurred in India in the early 1970s. Since then, the disease has spread to Pakistan, Bangladesh, Thailand, Myanmar, Indonesia, and the Philippines. The disease has become a significant impediment to the production of green gram, and its management is essential for producing sustainable crops.
Several management techniques can be utilized to manage YMD. Utilizing resistant varieties is one of the most efficient methods. Several green gram varieties with resistance to MYMIV have been developed, and their cultivation can substantially reduce the disease’s incidence and severity. Additionally, cultural practices such as opportune sowing, crop rotation, and weed control can aid in reducing the incidence of disease. Whiteflies, the virus’s vector, are susceptible to chemical control via insecticides.
Yellow Mosaic Disease Management in Green Gram
Causal organisms of Yellow Mosaic Disease
Yellow Mosaic Disease (YMD) in green gram is caused by the Mungbean yellow mosaic virus (MYMV) and Mungbean yellow mosaic India virus (MYMIV), depending on the geographic location. Both viruses belong to the genus Begomovirus, the family Geminiviridae. They have a unique, bipartite genome consisting of two circular single-stranded DNA molecules, DNA-A and DNA-B, encapsidated in geminate virus particles.
Disease Cycle of Yellow Mosaic Disease
Yellow Mosaic Disease (YMD) in green gram depends upon the transmission of the virus by Bemisia tabaci. During the feasting, the whitefly acquires the virus from infected green gram plants and then transmits it to healthy plants. Under favorable conditions, the disease can swiftly spread and result in substantial yield losses.
Summer-planted legumes are especially vulnerable to YMD. In addition to the green gram, several weed hosts, such as Croton sparsiflorus, Acalypha indica, and Eclipta alba, can function as a virus reservoir, thereby increasing the risk of infection.
Causes/Conditions Favorable for Yellow Mosaic Disease in the Field
Aphis gossypii can spread semi-persistent Yellow Mosaic Disease (YMD) in green gram. Warm summers boost aphid activity and reproduction, which can help spread the virus in the field. Thus, aphid frequency and activity affect YMD in green gram crops.