IITA IPM project 04: Characterizing
whiteflies and whitefly-associated symbionts associated with the pandemic of
severe CMD in East and Central Africa
Duration: 2 years (2003 to 2005)
Purpose: To study the
endosymbionts of the whitefly Bemisia
tabaci, determine how they influence whitefly biology, and assess the
potential for modifying these relationships to reduce whitefly abundance and
virus transmission activity.
Background/description: Bemisia tabaci, the vector of cassava mosaic viruses, is a highly diverse
species complex. Beyond simple genetic diversity, however, it seems that its
association with a diverse complement of symbionts may underlie its
diversification far more than realized. As endosymbionts are transmitted
horizontally and vertically, and a cursory examination has revealed at least
five kinds of B. tabaci-associated
bacteria, opportunities abound for gaining or losing individual or partial
complements of symbionts, foreseeably influencing differential host selection
and adaptation to different niches. However, the connection between phenotype
and symbiont complement is poorly understood, and so it is not yet possible to
capitalize on prokaryote composition for host manipulation to achieve more
benign B. tabaci behaviors. In this
project, in addition to trying to study the genetic diversity of B. tabaci biotypes, most particularly
those associated with the CMD pandemic in East and Central Africa, we will also
identify the diverse symbionts associated with a global collection of B. tabaci. The primary goal is to learn
more about the role of bacterial symbionts in fitness and development of biotypes
in the B. tabaci complex. In the long-term, this information could be
employed to manipulate whitefly phenotype with respect to symbiont, and thereby
alter its invasiveness, fitness, host response, and host range to lessen
whitefly damage to crop plants.
Agroecozone(s) and
location(s): Humid forests of East Africa
Expected outputs: a) Determination of
the occurrence of B. tabaci hybrids
using nuclear gene markers; b) Identification of prokaryotic endosymbionts
associated with B. tabaci on cassava and
their influence on B. tabaci biology;
c) Determination of begomoviruses associated with particular B. tabaci genotypes; d) Assessment of
the effect of B. tabaci genotype and
endosymbionts on life history traits and virus transmission; e) Transfer of technologies
developed to partners (principally IITA) in East Africa; f) Proposal of novel
approaches to managing CMD and B. tabaci
based on enhanced understanding of the CMD pathosystem, B. tabaci biotypes/genetic variability and endosymbiont
associations.
Potential impact and beneficiaries: Initial
beneficiaries: IITA scientists and researchers in the national research systems
of countries affected by CMD pandemic. Ultimately, cassava producers in the
affected region will benefit from improved cassava production arising from
enhanced management of B. tabaci.
Partners: a University of
Arizona (UA).
Development
investor(s): USAID’s US University Linkage Grants Programme
IITA contact
person(s)/principal investigator(s): James Legg J.Legg@cgiar.org website http://www.iita.org