Cassava leaves on healthier plants are dark green, have an even shape. African cassava mosaic virus acmv, east african cassava mosaic virus eacmv, and south african cassava mosaic virus sacmv are distinct species of circular singlestranded dna viruses that are whiteflytransmitted and primarily infect cassava plants. Cassava mosaic disease cmd is widespread, occurring in all countries in africa where cassava is grown. Pdf characterisation of sri lankan cassava mosaic virus. The main disease affecting the crop is african cassava mosaic.
However, the crop is susceptible to losses due to biotic stresses, in particular to viruses of the genus begomovirus family geminiviridae that cause cassava mosaic disease cmd. Impact of african cassava mosaic disease on the production. The control of african cassava mosaic virus disease. Two bipartite begomoviruses, indian cassava mosaic virus icmv and sri lankan cassava mosaic virus slcmv, have been isolated from mosaic diseased cassava originating from central india and sri lanka, respectively. Cassava mosaic disease cmd is a major constraint on cassava cultivation in africa. However not all cassava plants are affected as much as others. Other diseases like cassava bacterial blight cbb or those caused by fungi, like cassava. Surveillance for sri lankan cassava mosaic virus slcmv. Cassava diseases prevention and control to ensure food. The virus multiplies and occurs in large numbers in the leaves and stems. Cassava mosaic disease is known to be caused by viruses belonging to nine different begomovirus species in the african continent and the indian subcontinent.
African cassava mosaic virus acmv is a member of the genus begomovirus in the family geminiviridae. Name acronym genus family abutilon mosaic virus abmv begomovirus geminiviridae african cassava mosaic virus acmv begomovirus geminiviridae alfalfa mosaic virus amv alfamovirus bromoviridae. Euphorbiaceae is the only species in its genus that is cultivated as a food crop. Using transfer learning for imagebased cassava disease. Theories of regionalized variables and kriging were used to assess the incidence along the windexposed southwest field borders, disease spatial pattern of african cassava mosaic virus acmv. Cassava mosaic virus icmv and sri lankan cassava mosaic virus slcmv. Geminate structures of african cassava mosaic virus. Symptom severity of cassava mosaic disease in relation to. Effect of planting date and varietal resistance on the development of cassava mosaic virus disease in uganda. Deep learning for imagebased cassava disease detection.
Grafting position using cassava as scion or rootstock does not affect cmd display. A linearlike gradients, and other less obvious features. Laboratory manual for the diagnosis of cassava virus diseases. Occurrence of sri lankan cassava mosaic virus slcmv and. Acmv occurs virtually throughout the cassava growing areas of africa, with the apparent exception of coastal east africa, where eacmv occurs largely alone figure 1. Jan 20, 2003 the concentration of african cassava mosaic virus acmv was assessed by enzyme. Thresh natural resources institute, university of greenwich chatham maritime, kent me4 4tb, uk introduction vegetatively propagated crops are prone to virus infection and cassava manihot. Cassava mosaic disease and associated gemini viruses in. Cmd is caused by a virus belonging to the virus family, geminiviridae, and could be transmitted through two ways. Mosaic disease is caused by using infected cuttings. Control strategies for whitefly as a vector elysia slakie, caitlin mckee, angela gaffney, for cassava viral diseases c. Cassava virus diseases, in particular cassava mosaic disease cmd and cassava brown streak disease cbsd, have a longer history on the continent. The mosaic resistant varieties are developed for areas with high incidence of the disease.
The disease is endemic and is caused by seven distinct. Evaluation of resistance or tolerance to cassava mosaic, cassava brown streak viruses and cassava bacterial blight partners p1, p2 will evaluate also the incidence of cassava viruses and bacteria in the materials of the field trials at locations with high infection pressure. Dna forms of the geminivirus african cassava mosaic virus. Bemisia tabaci is confirmed as the vector of the disease by transmission studies and obtained amplification of 810 bp with cp primer from the b. Surveying cassava mosaic disease cmd and sri lankan. Mar 16, 2005 the effect of cassava mosaic geminiviruses on symptom severity, growth and root yield of a cassava mosaic virus disease. Indian cassava mosaic virus icmv and sri lankan cassava mosaic virus slcmv the type strain of icmv was isolated from mosaic affected cassava in southern india and originally regarded as a strain of acmv. Virus research 159, 161170 thresh jm, cooter rj, 2005. Cassava mosaic virus an overview sciencedirect topics. The biodiversity of geminiviruses associated with the cmd in india was investigated using pcr to specifically amplify the dna of indian cassava mosaic virus icmv or sri lankan cassava mosaic virus slcmv and also by using.
African cassava mosaic disease africa cassava mosaic disease acmd is the most important of all cassava diseases known in africa. This report consisted of positive virus detection from a single commercial plantation with symptomatic plants in ratanakiri province in eastern cambodia in may, 2015. African cassava mosaic virus acmv, east african cassava mosaic virus eacmv and south african cassava mosaic virus sacmv. In 2016, the first publication of the cassava mosaic disease cmd was published, reporting the unequivocal identification of the sri lankan cassava mosaic virus as responsible for cmd symptoms in the northeast of cambodia as early as 2015, although it is not known if the disease appeared first in this location and country. In africa, people also eat the leaves of the cassava as a green vegetable, which. This study was carried out to evaluate the current status of cassava mosaic disease incidence, severity, infection type, whitefly abundance in the farmers field as well as to determine the virus strains causing the disease in bauchi state. Differential primer pcr and rflps showed that african cassava mosaic virus. In 2016 sri lankan cassava mosaic virus slcmv was reported for the first time infecting cassava in southeast asia. Cassava mosaic disease, one of the ten most economically important crop viral diseases in the world, was first reported in southeast asia from a single plantation in cambodia in 2015. Eacmv occurs together with acmv in the great lakes zone of east and central africa. Cmd was of relatively minor importance until the 1980s, when a significant epidemic began in uganda. Analysis and mapping of the spatial spread of african. African cassava mosaic malawi virus, east african cassava mosaic zanzibar virus and south african cassava mosaic virus. Several laboratories are currently working on engineered resistance to geminiviruses in cassava.
Cassava mosaic virus is a very widespread disease of cassava in africa. Cassava virus evo why prioritize the cassava mosaic virus. Samura et al status and diversity of the cassava mosaic disease causal agents in sierra leone and distortion of the lower onethird of the leaflets. What are the symptoms of tapioca mosaic disease, structure of tapioca cassava mosaic virus. Cassava mosaic disease is one of the most important biotic constraint affecting cassava limiting the production potential of the crop in northern nigeria.
Cassava manihot esculenta crantz is one of the most important root staple crops in zambia. African cassava mosaic virus acmv, east african cassava mosaic cameroon virus and east african eacmcv cassava mosaic malawi virus eacmmv, and second, a technique based on restriction fragment length polymorphism rflp analysis of everse transcribed rt pcr r amplified cassava brown streak viruses species, cassava brown streak virus. After cesium sulfate density gradient centrifugation, they were separated into lighter top t and heavier bottom b components. Acmv was the first of 10 recognized and one tentative begomovirus species characterized from cassava plants affected by cassava mosaic disease cmd. Screening for cassava mosaic begomoviruses cmbsresistance using grafting and whitefly inoculation was performed with local and improved cassava. Refer to facts about improved cassava varieties in ghana for mosaic. The african cassava mosaic virus causes the leaves of the cassava plant to wither, limiting the growth of the root. The flies can also cause direct damage by feeding on the crop and causing root yield reductions.
African cassava mosaic virus acmv is a geminivirus spread by the whitefly bemisia tabaci. Resistant genotype nr 8083 had significantly lower symptom severity scores p cassava mosaic virus. Dna forms of the geminivirus african cassava mosaic virus consistent with a rolling circle mechanism of replication. An outbreak of the virus in africa in the 1920s led to a major famine. Laboratory manual for the diagnosis of cassava virus diseases is prepared for the benefit of participants of the regional training for the disease objective of great lakes cassava initiative glci on cassava viruses. Control strategies for whitefly as a vector for cassava. In fact, tapioca is a starch extracted from the cassava root through a process of washing and pulping. Icmv is the usual virus causing cmd in india and sri lanka and has not been detected elsewhere. During feeding, the insect injects saliva containing the virus into cassava leaves. Cassava mosaic disease cmd is caused by whiteflytransmitted geminiviruses and is a. Cassava mosaic disease cmd is caused by whiteflyborne viruses of the genus begomovirus family geminiviridae. In india, two begomoviruses, indian cassava mosaic virus hong et al.
Epidemiology of cassava mosaic disease in coast province, kenya by a. In addition to these species, several strains have been recognized that exhibit contrasting phenotypes and infection dynamics. Yield losses due to cassava mosaic disease range between 2095% in susceptible. African cassava mosaic virus acmv, east african cassava mosaic virus eacmv, and south african cassava mosaic virus sacmv are distinct species of circular singlestranded dna viruses that are whitefly transmitted and primarily infect cassava plants. Session b the factors properties and geographical variation of gemini virus isolates from mosaic affected cassava harrison, b. Partial control of the spread of african cassava mosaic virus in benin by intercropping. Cassava mosaic disease cmd is a widespread viral disease that causes high yield losses in susceptible genotypes in subsaharan africa. A study was conducted through a survey to determine the status of cmd and slcmv in farmers. Pdf on jun 1, 1990, claude fauquet and others published african cassava mosaic virus. African cassava mosaic virus an overview sciencedirect topics. Etiology, epidemiology, and control cassava munihor escuknra crante. African cassava mosaic virus african cassava mosaic. The results show that the tested cultivars differed significantly in terms of severity of the virus, harvest index and tuber production p cassava mosaic virus icmv and sri lankan cassava mosaic virus slcmv are members of the genus begomovirus family geminiviridae. Eastern and southern africa regional centre, p o box 7878, kampala, uganda.
Like other cassava mosaic geminiviruses cmgs such as african cassava mosaic virus acmv and east african cassava mosaic virus eacmv, both icmv and slcmv posses bipartite ssdna genomes and are transmitted. Cassava is a major factor in food security across subsaharan africa. Distribution of cassava mosaic geminiviruses in africa. Two types of geminate structures were purified from african cassava mosaic geminivirus acmvinfected nicotiana benthamiana plants and analyzed by electron cryomicroscopy and image reconstruction. Oct 07, 2016 cassava mosaic disease is the very severe and widespread in subsaharan africa. Cassava can grow under drought, high temperature and poor soil conditions, but its production is severely limited by viral diseases. The onset of symptom appearance and the evolution of cassava mosaic disease cmd varied in function of genotypes and virus inoculation techniques used. In south america, the main viral diseases are caused by the cassava common mosaic virus cscmv and by the cassava frogskin virus cfsv. Fargette cassava manihot esculenta crantz is an important staple food crop in many parts of subsaharan africa. The results show that the tested cultivars differed significantly in terms of severity of the virus, harvest index and tuber production p cassava mosaic and cassava brown streak virus diseases in africa.
This leads to the production of no tubers or few depending. Cassava mosaic virus disease cmd is caused by cassava mosaic geminiviruses cmgs, in the family geminiviridae and genus begomovirus. The virus is found only in africa, where it is widespread. Status and diversity of the cassava mosaic disease causal. The mottling and twisting of cassava leaves at touns field is a manifestation of cassava mosaic disease or cmd. The virus is spread by the whitefly and by the transplanting of diseased plants into new fields. Cmb infected crops produce several foliar symptoms including mottling, misshapen, mosaic and twisted leaflets and a reduction in the size of leaves and plants. Ugandan variant of the eastern africa cassava mosaic virus. The effect of cassava mosaic geminiviruses on symptom. However, the terms tapioca and cassava are used as synonyms. A novel recombinant cmg east african cassava mosaic virus uganda was associated with the severe cmd pandemic, which was. Analysis and mapping of the spatial spread of african cassava. Legg,e graham thompson,f joe tohme,g theresa aveling,h jose t. In recent years, sri lankan cassava mosaic virus slcmv, a begomovirus genus begmovirus, family geminiviridae causing cassava mosaic disease in asia, poses serious threats to cassava.
Cassava brown streak virus disease in coastal areas of eastern and southern africa and cassava mosaic virus disease in all regions, are two of the most important biotic constraints and greatly. With minimum maintenance, the farmers can dig up the starchy root of the cassava and eat it 6 months to 3 years after planting. An estimated 30% of zambians, over 4 million people, consume cassava as part of their daily diet. Pdf characterisation of sri lankan cassava mosaic virus and. Impact of african cassava mosaic disease on the production of. During the 1990s, an epidemic of cmd severely hindered cassava production across eastern and central africa. Surveillance for sri lankan cassava mosaic virus slcmv in. The concentration of african cassava mosaic virus acmv was assessed by enzyme. Evolution of african cassava mosaic virus by recombination between. However, the productivity of cassava in subsaharan africa is generally low, in part due to the deleterious effects of pests and diseases. To determine the presence and incidence of sri lankan cassava mosaic virus slcmv one year after first detection, a total of 6,480 samples from 419 fields were systematically collected from. Epidemiology of cassava mosaic disease and molecular characterization of cassava mosaic viruses and their associated whitefly bemisia tabaci vector in south africa kenneth gaza mabasa a dissertation submitted to the school of molecular and cell biology, faculty of. Cassava mosaic disease ppt symptoms, causal organism, etiology and control measures cassava mosaic disease, tapioca mosaic disease, tapioca mosaic virus, causal organism of tapioca mosaic disease, how to control cassava mosaic disease. Almost all traditional cultivars of cassava cultivated in different countries on the african continent are susceptible to this disease.
The main disease affecting the crop is african cassava mosaic disease. W, gashaka g, mkamilo g, alicai t, lava kumar p, 2011 comparing the regional epidemiology of the cassava mosaic and cassava brown streak virus pandemics in africa. Virus or african cassava mosaic disease, caused by a virus transmitted by the whitefly bemisia tabaci, which is abundant at the start of the rainy season and disappears in the dry season. The effects of cassava mosaic disease cmd on growth and yield components were systematically determined on 14 different cassava genotypes in yangambi. Cassava plays a key role in the food security of subsaharan africa, but as a vegetatively propagated crop, it is particularly vulnerable to the effects of virus diseases and these therefore represent a major threat to the livelihoods of millions of africans. Pdf first report of sri lankan cassava mosaic virus. Emergency prevention system for transboundary animal and plant pests and diseases. Pdf cassava mosaic disease and associated viruses in zambia. The effect of cassava mosaic geminiviruses on symptom severity, growth and root yield of a cassava mosaic virus disease.
Ratanakiri, tbong khmum, pursat and battambang in february 2016 in cambodia. Pdf cassava mosaic disease cmd is caused by cassava mosaic begomoviruses cmbs, which are transmitted by the whitefly bemisia. Effective control of cmd is beneficial and justifiable since. Control strategies for whitefly as a vector for cassava viral. Effectiveness of phytosanitation in cassava mosaic disease. Cassava mosaic disease africa soil health consortium. Strategies for controlling cassava mosaic virus disease in.
Cassava provides a major source of calories for poor families, because of its high starch content. Sometime in the late1980s, a mutation occurred in uganda that. Using transfer learning for imagebased cassava disease detection. Nine viruses have been isolated from african cassava. Genetic diversity and phylogeography of cassava mosaic. Indian cassava mosaic virus icmv was the first cmg to be recorded from south asia malathi et al. Cassava munihor escuknra crante euphorbiaceae is the only species in its genus that is. Mosaic disease was the first to be recorded in tanzania towards the end of the 19th century warburg, 1894. Oct 27, 2017 cassava virus diseases, in particular cassava mosaic disease cmd and cassava brown streak disease cbsd, have a longer history on the continent. Strategies for controlling cassava mosaic virus disease in africa. Cultivation of cassava is hampered by several biotic constraints, of which cassava mosaic disease cmd is currently the. Like other cassava mosaic geminiviruses cmgs such as african cassava mosaic virus acmv and east african cassava mosaic virus eacmv, both icmv and slcmv posses bipartite ssdna genomes and are transmitted by whiteflies of the bemisia tabaci.
K saunders, a lucy, and j stanley department of virus research, john innes institute, john innes centre for plant science research, norwich, uk. To determine the presence and incidence of sri lankan cassava mosaic virus slcmv one year after first detection, a total of 6,480 samples from 419 fields were systematically collected from cassava production. Seift h,ve of nfro cassava mosaic disease is the very severe and widespread in subsaharan africa. Cassava mosaic disease cmd is one of the most economically important crop diseases in africa.