Occurrence of three genotypic clusters of Bemisia tabaci and the rapid spread of the B biotype in south India

Rekha, A.R., Maruthi, M.N., Muniyappa, V. and Colvin, John (2005) Occurrence of three genotypic clusters of Bemisia tabaci and the rapid spread of the B biotype in south India. Entomologia Experimentalis et Applicata, 117 (3). pp. 221-233. ISSN 0013-8703

Abstract

The whitefly,
Bemisia tabaci
(Gennadius) (Homoptera: Aleyrodidae), is generally considered to have
originated from the Indian subcontinent, although little information has so far been collected on the
molecular diversity of populations present in this region. The genetic diversity of
B. tabaci
populations
from Karnataka State, south India was analysed using the random amplified polymorphic DNApolymerase
chain reaction (RAPD-PCR) technique and partial mitochondrial cytochrome oxidase I
(mtCOI) gene sequences (689 bases) of 22 selected samples. A total of 108 whitefly samples analysed
by RAPD-PCR produced 89 polymorphic bands, and cluster analyses grouped them according to
their geographic origin into ‘north’ and ‘south’ Karnataka. Phylogenetic analysis of mtCOI gene
sequences with reference
B. tabaci
sequences from other Asian countries divided them into three genotypic
clusters. Each cluster was supported with high bootstrap values (82–100%) and the individuals
belonging to each cluster shared high nucleotide identities (up to 100%). This indicated at least three
distinct genotypes, apparently indigenous to India, which are also present in China, Malaysia, Nepal,
Pakistan, and Thailand. These coexist with the B biotype, which was first reported in India in 1999,
and has since spread rapidly to other states in south India. The B biotype was more common than the
indigenous
B. tabaci
, in locations where it had been present for more than 2 years. This is reminiscent
of the situation in the Americas during the early 1990s, where the B biotype replaced existing
biotypes and caused unprecedented losses to agriculture.

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