Genetic Diversity of Mitochondrial DNA of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) Associated with Cassava and the Occurrence of Cassava Mosaic Disease in Zambia

Abstract

Bemisia tabaci is an important vector of cassava brown streak viruses and cassava mosaic begomoviruses, the causal agents of cassava brown streak disease and cassava mosaic disease (CMD), respectively. A study was carried out to determine the genetic variability of B. tabaci associated with cassava and the occurrence of CMD in Zambia in 2013 and 2015. Phylogenetic analysis showed the presence of only the sub-Saharan Africa 1 (SSA1) genetic group in Zambia. The SSA1 population had three population subgroups (SGs): SSA1-SG1, SSA1-SG2 and SSA1-SG3. All three SSA1 population subgroups occurred in Western Province. However, only SSA1-SG3 occurred in Eastern Province, while only SSA1-SG1 occurred in North Western and Luapula Provinces. Adult B. tabaci were most abundant in Western Province in 2013 (11.1/plant) and 2015 (10.8/plant), and least abundant (0.2/plant) in Northern Province in both 2013 and 2015. CMD was prevalent in all seven provinces surveyed, with the highest incidence recorded in Lusaka Province in both 2013 (78%) and 2015 (83.6%), and the lowest in Northern Province in both 2013 (26.6%) and 2015 (29.3%). Although SSA1-SG1 occurred at greater abundances than the other subgroups, there was no direct association demonstrated between whitefly subgroup and incidence of CMD. Establishing which B. tabaci genetic groups and populations are associated with CMD and their distribution in the country is a key factor in guiding the development of CMD control strategies for cassava-dependent households.

Epidemiological Analysis of Cassava Mosaic and Brown Streak Diseases, and Bemisia tabaci in the Comoros Islands

“…It also differs from previous studies considering B. tabaci from coastal East Africa which only reported mitotype SSA1-SG3 [ 19 , 44 ]. This is also the first report of mitotype SSA1-SG2 outside continental Africa as so far it has only been reported from Central African Republic, Democratic Republic of Congo, Kenya, Tanzania, Uganda, and Zambia [ 19 , 62 , 64 , 65 ].…”

Is High Whitefly Abundance on Cassava in Sub-Saharan Africa Driven by Biological Traits of a Specific, Cryptic Bemisia tabaci Species?

“…In addition to the reports of SSA1-SG3 species being less abundant in the field and less fecund under standardized conditions [ 25 , 34 , 45 , 46 ], parasitism could be another ‘biological brake’ contributing to the low field populations of this B. tabaci whitefly species [ 23 , 47 , 48 ]. Caution should be taken, however, in drawing conclusions from data obtained using a single SSA1-SG3 whitefly population.…”

“…Contrasting results from field surveys are not surprising, with a range of factors including environment and climate influencing the abundance, distribution, life history and fitness of whitefly populations in a landscape. For example, rapid leaf growth caused by high temperatures and rainfall boost whitefly populations [ 5 , 24 , 25 , 26 ]. Young (1–4 months of age) cassava plants harbor more whitefly than older (>5 months) cassava plants [ 27 ].…”

Evidence for Upholding the Association of Whitefly Species Bemisia tabaci and Trialeurodes vaporariorum with Tomato Yellow Leaf Curl Virus

“…For a better understanding between the virus and the associated vector, serological assay mainly DAS-ELISA is used which not only helps in detecting the virus in symptomatic plants but also helps in determining the virus particles in the gut of those vectors transmitting them in a circulative persistent manner 15,16 . However, molecular assays like PCR help in characterizing the exact identity of the insect vectors like whitefly which are very small to identify in the techniques of the field like PCR are widely used 17,18 .…”