Nine species of cassava-infecting geminiviruses have been identified between Africa and India based on genomic sequencing and phylogenetic analysis.

[2] In 1971, a resistant line of cassava, the predominant host of the pathogen, was established and used by the International Institute of Tropical Agriculture in Nigeria.

However, in the late 20th century, a more virulent virus broke out in Uganda and quickly spread to East and Central Africa.

[2] Though management practices are useful, the viruses’ high rate of recombination and co-infection capabilities have caused CMD to be one of the most detrimental diseases affecting food supply in Africa.

Plants use gene silencing to suppress viral replication, though begomoviruses have evolved a counter-acting suppressor protein against this natural host defense.

The host range depends on the species of virus and most are able to be transmitted and to cause disease on plants of the genera Nicotiana and Datura.

[9] Cassava geminiviruses[10] are transmitted in a persistent manner by the whitefly Bemisia tabaci, by vegetative propagation using cuttings from infected plants, and occasionally by mechanical means.

[14] As the genome of the viruses has two components, DNA A and B, that are encapsidated in separate geminate particles, it requires a double inoculation to cause infection.

[15] The severity of cassava mosaic disease is impacted by environmental factors such as light intensity, wind, rainfall, plant density and temperature.

[12] Whiteflies can fly at speeds up to 0.2 mph, and in high-wind conditions they can move much greater distances in a shorter time, thus increasing rate of virus spread.

[13] Thus, plant density impacts the spread of the virus, with low-density fields encouraging faster disease propagation than high-density ones.

[12] Little to no infection occurs after three months, and variation in spread was due to change in temperature, radiation and population levels of whitefly.

This strategy does not protect them from being inoculated by whiteflies, but research shows that the virus is more aggressive in plants infected from contaminated cuttings than by insect vectors.

[13] For example, hybrids that are a result of crossing cassava and other species, such as Manihot melanobasis and M. glaziovii, have been shown to have considerable resistance to CMV.

[6] The CABI-led programme, Plantwise suggests intercropping with cereals and legumes, such as maize or cowpeas, to repel whiteflies and rotate cassava with non-host crops including sorghum.

[6] The Ministry of Agriculture Food Security and Cooperatives of Tanzania recommend uprooting diseased plants once every week by pulling them out by hand.

[1] Although cassava is also cultivated in Latin America and South East Asia, the geminiviruses infecting it are only found in Africa and the Indian sub-continent.

[1] The Ministry of Agriculture Food Security and Cooperatives of Tanzania recommend uprooting diseased plants once every week by pulling them out by hand.