Prevalence and genetic diversity of endosymbiotic bacteria infecting cassava whiteflies in Africa

Abstract

BackgroundCassava provides over half of the dietary requirement for more than 200 million poor in Africa. In recent years, cassava has been affected by an epidemic of a virus disease called cassava brown streak disease (CBSD) that is spreading in much of eastern and central Africa, affecting food security and the economic development of the poor. The viruses that cause CBSD are transmitted by the insect vector whitefly (Bemisia tabaci), which have increased to very high numbers in some African countries. Strains of endosymbiotic bacteria infecting whiteflies have been reported to interact specifically with different whitefly populations with varied effects on its host biology and efficiency of virus transmission. The main aim of this study was therefore to investigate the prevalence and diversity of the secondary endosymbiotic bacteria infecting cassava whiteflies with a view to better understand their role on insect population dynamics and virus disease epidemics.ResultsThe genetic diversity of field-collected whitefly from Tanzania, Malawi, Uganda and Nigeria was determined by mitochondrial DNA based phylogeny and restriction fragment length polymorphism. Cassava in these countries was infected with five whitefly populations, and each one was infected with different endosymbiotic bacteria. Incidences of Arsenophonus, Rickettsia, Wolbachia and Cardinium varied amongst the populations. Wolbachia was the most predominant symbiont with infection levels varying from 21 to 97%. Infection levels of Arsenophonus varied from 17 to 64% and that of Rickettsia was 0 to 53%. Hamiltonella and Fritschea were absent in all the samples. Multiple locus sequence typing identified four different strains of Wolbachia infecting cassava whiteflies. A common strain of Wolbachia infected the whitefly population Sub-Saharan Africa 1-subgroup 1 (SSA1-SG1) and SSA1-SG2, while others were infected with different strains. Phylogeny based on 16S rDNA of Rickettsia and 23S rDNA of Arsenophonus also identified distinct strains.ConclusionsGenetically diverse bacteria infect cassava whiteflies in Africa with varied prevalence across different host populations, which may affect their whitefly biology. Further studies are required to investigate the role of endosymbionts to better understand the whitefly population dynamics.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-015-0425-5) contains supplementary material, which is available to authorized users.

Genetic Diversity of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) Colonizing Sweet Potato and Cassava in South Sudan

“…Insects 2020, 11, 58 3 of 15 SSA1 has been separated into five sub-groups: SSA-subgroup1 (SSA1-SG1), SSA1-SG2, SSA1-SG3, SSA1-SG4, and SSA1-SG5 [10,58,[62][63][64][65].…”

On species delimitation, hybridization and population structure of cassava whitefly in Africa

“…Previously, Legg et al (2014) reported that the SSA1-SG1, representing the major 450 SSA1 mtCOI subgroup, was implicated in the severe CMD pandemic in East Africa. Based 451 on the subgroup classification, Wosula et al (2017) reclassified these SSA1-SG1 individuals 452 into three SNP-based groups of SSA-ECA, SSA-CA, and SSA-WA due to perceived 453 inconsistencies (e.g., SSA1-SG3, SSA1-SG5; see Ghosh et al (2015)) based solely on the 454 utilization of the short (i.e., ca. 657bp) mtCOI partial gene marker.…”

Cassava whitefly,Bemisia tabaci(Gennadius) (Hemiptera: Aleyrodidae) in East African farming landscapes: a review of the factors determining abundance

“…Most B. tabaci collected from cassava were SSA1 and most were uninfected by any of the secondary symbionts. A later study found contrasting results (Ghosh et al , 2015). Samples of B. tabaci were collected from cassava crops across East African countries were found to be infected with a range of endosymbionts, with the predominant species being Wolbachia , Rickettsia and Arsenophonus .…”

“…Some evidence exists that endosymbiotic bacteria within B. tabaci can have both positive and negative effects on B. tabaci fitness (Kontsedalov et al , 2008; Himler et al , 2011; Ghosh et al , 2015). Portiera aleyrodidarum is a primary obligate bacterial endosymbiont of B. tabaci , and is essential to their development.…”