Some highlights of CBSD research at
NaCRRI
National Cassava Research Programme
National Crops Resources Research Institute
(NaCRRI), NARO
Key Milestones in history of CBSD
On-going CBSD research activities
Emerging ideas on CBSD
Where we are located
Hellen Apio
NaCRRI, Namulonge
Year
Key Historic Highlights
1935
1st report in Tanzania (Storey, 1936)
1945
1st report in UG, introduced from TZ (Jameson, 1964)
1946
Sap transmission (Lister, 1959)
1950
Details of symptoms, report in Kenya (Nichols, 1950)
1946
Virus-like particles under EM ( Kitajama & Costa, 1964)
1994
CBSD re-appears in Uganda (Thresh et al., 1994)
1995
Tolerance identified in a landrace in TZ (Hillocks et al.,)
2000
Re-appears in Kenya (Munga et al., unp.)
2000
Gen. Ipomovirus, Fam. Potyviridae (Monger et. al., 2001a)
2000
PCR diagnostic test (Monger et. al., 2001b)
2004
CBSD re-emerges in Uganda (Alicai et al., 2007)
2005
1st National Consultative Workshop on CBSD
2005
CBSV transmission by whiteflies Bemisia tabaci (Maruthi et al., 2005)
2009
Two genetically distinct strains of CBSV (Mbazibwa et al. 2009)
2009
1st Complete CBSV genome sequence (Mbazibwa et al. 2009)
2009
Evidence of CBSV transmission by spiralling whiteflies (Mware et al.,2009(b))
2009
1st CBSV antibodies for use in ELISA (Winter et al., 2009)
2010
CBSD International Workshop in Uganda
2005
Districts
surveyed
18
2007
Districts
with CBSD
4
Districts
surveyed
20
CBSD Incidence in
Uganda 2009
2008
Districts
with CBSD
8
Districts
surveyed
25
Districts
with CBSD
18
“Biotechnology Applications to Combat Cassava Brown
Streak Disease” (2010 – 2013): Tanzania, Uganda & IITA
Improve existing markers for CBSD field resistance from Namikonga:
Fine map genomic regions showing QTLs;
transcriptome sequencing;
Generate SNP resources;
Develop new markers and breeding resources for new sources of field
resistance to CBSD:
markers linked to new sources of resistance; (AR400-6; NDL06/132)
Test strain x genotype effects; (AR40-6, Mkombozi, Muzege, Mufarasa, I96/1089A)
Generate partial inbred lines -12 parental lines
Utilize markers in Tanzania and Uganda to begin breeding new CBSD-resistant
cultivars suitable for the region:
Uganda: Namikonga X (TME14, MM96/4271, NASE12, MH97/2961)
Tanzania Namikonga X (AR37-80; Mreteta; Libaga; Albert)
Test a transgenic approach to controlling CBSD:
7 siRNA lines derived from FL
7 siRNA lines derived from N-terminal
2 non-trangenic (TMS60444 & Ebwanatereka)
Towards understanding and developing varieties resistant to
cassava brown streak virus disease in Uganda
Determine the genetic diversity and population structure of CBSV in Uganda;
Isolates from Uganda + controls
Symptom variability
Determine the rate of spread and impact on growth of CBSV infection in
Cassava:
3 locations;
3 varieties
inoculation levels
Identify sources of CBSD resistance genes from both local and introduced
cassava germplasm:
116 genotypes field evaluated
116 genotyped with 30 SSR markers
Understand the genetics of CBSD:
Genetic analysis of F1s
S1 evaluations;
mapping in one family
Regional project under CRCoE
• Four target countries: Uganda, Kenya, Tanzania & Ethiopia
• Concept of genetic stocks
– Genetic stocks that combine CMD & CBSD resistance
– Genetic stocks that combine CMD & CBSD resistance with beta
carotene
– Genetic stocks that combine CMD & CBSD resistance with earlybulking
– Genetic stocks that combine CMD, CBSD & whitefly resistance
• Establishment of core collection
• Validation of CBSD markers associated with different sources
of resistance
• Advance back-up cassava breeding materials
Emerging ideas on CBSD
• Breeding programmes vision
– “Superb” variety
– Can be achieved or missed- several examples
– If missed go with best alternative
stabilize/ increase
production
– Meantime Tolerance + Phytosanitation for CBSD
• Back-up CBSD resistance breeding; reflect on the past
– Wild relatives; phenomenal progress made between 1930s to 1950s
– Cultivated cassava; post-independence tolerance/ partial resistance
– All countries to evaluate available germplasm in hot spots
• Fine-tuning CBSD evaluations protocols
– Standardize phenotypic scores; leaf vs stem symptoms!
– Combine quantitative with qualitative measures
– Increasing evidence of genotype x strain interaction; story of the 8
clones
Thank
you