Legume yellow mosaic viruses: genetically isolated begomoviruses

Abstract

SUMMARY The yellow mosaic diseases of a number of legumes across Southern Asia are caused by four species of whitefly‐transmitted geminiviruses (genus Begomovirus, family Geminiviridae): Mungbean yellow mosaic virus, Mungbean yellow mosaic India virus, Dolichos yellow mosaic virus and Horsegram yellow mosaic virus. They cause losses to a number of important pulse crops, a major source of dietary protein in the region. The viruses have host ranges limited to plants of the family Fabaceae and efforts to limit losses are hampered by limited availability of conventional resistance sources and/or the lack of durability of the resistance that has been identified. There is ample evidence for genetic interaction between these begomoviruses within the legumes, in the form of both classical recombination and component exchange, but little evidence for interaction with viruses that infect other plants. This is indicative of genetic isolation, the viruses in legumes evolving independently of the begomoviruses in plant species of other families. This has implications for the development of engineered resistance in legumes, which holds the promise of durability but has yet to be transferred to the field. Taxonomy: The viruses causing yellow mosaic diseases of legumes across southern Asia, four of which have been identified so far, are bipartite begomoviruses (genus Begomovirus, family Geminiviridae): Mungbean yellow mosaic virus, Mungbean yellow mosaic India virus, Horsegram yellow mosaic virus and Dolichos yellow mosaic virus. Physical properties: The legume yellow mosaic viruses (LYMVs), like all members of the Geminiviridae, have geminate (twinned) particles, 18–20 nm in diameter, 30 nm long, apparently consisting of two incomplete T = 1 icosahedra joined together in a structure with 22 pentameric capsomers and 110 identical protein subunits. Disease symptoms: Symptoms caused by LYMVs are largely dependent on host species and susceptibility. Initially symptoms appear as small yellow specks along the veins and then spread over the leaf. In severe infections the entire leaf may become chlorotic. In blackgram the chlorotic areas sometimes turn necrotic. Infections of French bean usually do not produce a mosaic but instead induce a downward leaf curling. Disease control: Control is based mainly on preventing the establishment of the whitefly vector, Bemisia tabaci, in the crop by application of insecticides. Changes in agricultural practices, such as moving the cropping period out of periods of high vector incidence (the wet period in late summer) to times of low vector incidence (dry season in early summer) have met with some, albeit short‐term, benefits. The use of natural, host plant resistance is efficacious, although the available sources of resistance in most legume crops are limited. In mungbean the resistance is attributed to two recessive genes which are used effectively to control the disease. Useful websites: http://www.danforthcentre.org/iltab/geminiviridae/, http://www.iwglvv.org/

Molecular detection and characterisation of Horsegram Yellow Mosaic Virus (HgYMV) infecting Lima bean (Phaseolus lunatus) in India

“…several conditions. In addition, there was also the In addition, our data showed that the genome possibility that the samples collected based on organisation of HgYMV-Lb was most similar to that of a symptoms phenotype can be caused by other typical begomovirus bipartite genome reported by pathogens, which are undetectable in PCR previous studies (Qazi et al, 2007;Monger et al, 2010; technique using begomovirus-specific primers.…”

“…The present finding was consistent study were compared with sequences from other with the previous studies, which showed predictable begomoviruses deposited in Gene bank. Thus, relatedness of HgYMV and MYMV (Qazi et al, 2007; complete sequences of the DNA-A component and Manjunatha et al, 2015) and MYMIV (Manjunatha et al, DNA-B component were determined. Similar to the 2015;Rienzieet al, 2016).…”

“…Similar to the 2015;Rienzieet al, 2016). results obtained by previous studies (Padidam et In conclusion, the PCR analysis with al., 1995; Seal et al, 2006;Qazi et al, 2007) No funding support for this study, rather all DNA-A and DNA-B sequences were most similar to facilities/consumables were provided by the Natural…”

“…mosaic symptoms and is easily transmitted by whitefly Lima beans are rich in fiber which helps to vector Bemisia tabaci (Order Hemiptera, family: eliminate cholesterol from the body (Gobertson, Aleyrodidae) (Pant et al, 2001;Maruthi et al, 2006;2004). The beans are a good source of potassium, Qazi et al, 2007). Initially, the symptoms caused by iron, copper and manganese.…”

“…Initially, the symptoms caused by iron, copper and manganese. As it contain high Yellow mosaic virus appear as small yellow specks along potassium and low sodium, thus help reduce blood the veins and then spread over the leaf and are largely pressure (Kathirvel and Kumudha, 2011 (Collins, 2007; begomoviruses (Pant et al, 2001;Maruthi et al, 2007;Kathirvel and Kumudha, 2011).The wild Lima bean seeds have high levels of glucosides which Qazi et al, 2007). Thus, Yellow mosaic virus infecting lima bean from India sub-continent has not yet been breakdown to toxic hydrocyanic acid when the characterized.…”