Strategies for controlling cassava mosaic virus disease in Africa

Abstract

Cassava mosaic disease (CMD) is caused by whiteflyborne viruses of the genus Begomovirus (family Geminiviridae ). The disease has long been regarded as the most important of those affecting cassava in sub-Saharan Africa, and has been the subject of much research, especially since the onset of the current very damaging pandemic in eastern and central Africa. This review considers the main features of CMD and the various possible means of control. The main emphasis to date has been on the development and deployment of virus-resistant varieties. These are widely adopted in countries where CMD has caused serious problems, and provided a powerful incentive for farmers to abandon some of the most susceptible of their traditional varieties. Only limited use has been made of phytosanitation involving CMD-free planting material and the removal (roguing) of diseased plants. Cultural methods of control using varietal mixtures, intercrops or other cropping practices have also been neglected, and there is a need for much additional research before they can be deployed effectively. Nevertheless, the severe losses now being caused by CMD in many parts of sub-Saharan Africa could be greatly decreased through the application of existing knowledge.

Characterization of Brown Streak Virus–Resistant Cassava

“…While CMD has long been viewed as the main constraint to cassava production in Africa (Seif, 1982;OtimNape et al, 1997), CBSD has recently become a major problem due to its reemergence in East Africa and its rapid spread into new geographical areas in central African countries (Alicai et al, 2007;Bigirimana et al, 2011;Mulimbi et al, 2012;Patil et al, 2015). Viral disease management in cassava fields has mostly relied on the identification of existing sources of virus resistance, the introgression of virus resistance traits into farmer-preferred cultivars and the deployment of virus-resistant varieties in the field (Thresh and Cooter, 2005). These strategies have been particularly important for mitigating the impact of CMD in the CMD pandemic regions of Africa (Legg et al, 2006).…”

Disease control and its selection for damaging plant virus strains in vegetatively propagated staple food crops; a theoretical assessment

“…We show how this approach, linking transmission mode and disease control with virus titre, can be applied to an example of disease control in staple food crops to identify strategies with high or with low risk of failure. Whether or not a particular strategy for control of plant viruses is implemented by farmers depends on a wide range of socio-economic and cultural drivers (Thresh & Cooter 2005) in addition to the effectiveness of control. Nevertheless, we contend that in allowing an assessment of the risk of long-term failure of control, the methods developed in this paper have an important role to play in the selection and implementation of control strategies for virus diseases of vegetatively propagated crops.…”

“…are among the main constraints to sustainable production of these vegetatively propagated staple food crops in lesser developed countries (Dahal et al 1997;Rybicki & Pietersen 1999;Gibson & Aritua 2002;Thresh & Cooter 2005). New viral strains frequently emerge (Rybicki & Pietersen 1999;Boulton 2003;Varma & Malathi 2003;Seal et al 2006); some with devastating consequences, such as the current pandemic of a new strain of the virus causing cassava mosaic disease (CMD) in Africa (Gibson et al 1996).…”

“…These strategies include plant breeding for resistance to the virus (Fargette et al 1996;Aritua et al 1998;Morales 2001;Lapidot & Friedmann 2002;Diaz-Pendon et al 2004;Ariyo et al 2005;Thresh & Cooter 2005), the control of vectors (Palumbo et al 2001), as well as crop sanitation through removal of diseased plants (Gibson & Aritua 2002;Thresh & Cooter 2005) and improved selection/production of planting material (Thro et al 1999;Feng et al 2000;Monger et al 2001;Gibson & Aritua 2002;Alleman et al 2004) for these vegetatively propagated crops.…”

Molecular-assisted selection for resistance to cassava mosaic disease in Manihot esculenta Crantz

“…According to these authors, the genetic resistance that was derived from M. glaziovii is polygenic, with recessive inheritance and a heritability of 0.60. Hybrids resulting from a cross between M. esculenta and M. glaziovii, known as Tropical Manihot Species (TMS), have been used as a CMD resistance source in Africa (Legg and Fauquet, 2004;Thresh and Cooter, 2005), although the results of this introgression in cultivated species have not shown great success in recent years (Rabbi et al, 2014).…”