Abstract:
Cassava brown streak disease (CBSD) is emerging as one of the
most important viral diseases of cassava (Manihotesculenta) and
is considered today as the biggest threat to cassava cultivation in
East Africa. The disease is caused by isolates of at least two
phylogenetically distinct species of single-stranded RNA viruses
belonging to the family Potyviridae, genus Ipomovirus. The two
species are present predominantly in the coastal lowland
[Cassava brown streak virus (CBSV);Tanzania and Mozambique]
and highland [Cassava brown streak Uganda virus (CBSUV);Lake
Victoria Basin,Uganda,Kenya and Malawi] in East Africa. In this
study, we demonstrate that CBSD can be efficiently controlled
using RNA interference (RNAi).Three RNAi constructs targeting
the highland species were generated, consisting of the full-length
(FL; 894 nucleotides), 397-nucleotide N-terminal and 491nucleotide
C-terminal portions of the coat protein (CP) gene of a
Ugandan isolate of CBSUV (CBSUV-[UG:Nam:04]), and expressed
constitutively in Nicotiana benthamiana. After challenge with
CBSUV-[UG:Nam:04], plants homozygous for FL-CP showed the
highest resistance, followed by the N-terminal and C-terminal
lines with similar resistance.In the case of FL,approximately 85% ofthetransgenicplantlinesproducedwerecompletelyresistant.
Some transgenic lines were also challenged with six distinct
isolates representing both species:CBSV and CBSUV.In addition
to nearly complete resistance to the homologous virus, two FL
plant lines showed 100% resistance and two C-terminal lines
expressed 50–100% resistance, whereas the N-terminal lines
succumbed to the nonhomologous CBSV isolates.Northern blotting
revealed a positive correlation between the level of
transgene-specific small interfering RNAs detected in transgenic plants and the level of virus resistance.Thisisthefirstdemonstration
of RNAi-mediated resistance to CBSD and protection across
very distant isolates (more than 25% in nucleotide sequence)
belonging to two different species: Cassava brown streak virus
and Cassava brown streak Uganda virus.
Language:
English
Date of publication:
2010
Journal:
Collection:
RUFORUM Journal Articles
Agris Subject Categories:
Agrovoc terms:
Additional keywords:
Licence conditions:
Open Access
Access restriction:
Form:
Printed resource
Publisher:
ISSN:
E_ISSN:
Edition:
Extent:
1-11