Cassava brown streak epidemiology in the Eastern Democratic Republic of the Congo. Cassava brown streak Disease in Eastern DRC

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IITA is a member of the CGIAR System Organization.
"Cassava brown streak epidemiology in Eastern Democratic
Republic of the Congo."
Date: Wednesday 7th July 2021
Location: Virtual
By
Clerisse Casinga, Everlyne Wosula, Rudolph Shirima, Sikirou Mouritala, Benoit Dhed’a, Wily Tata-
Hangy, Henry Ugentho, Carine Munyerenkana, Benoit Bashizi, Godefroid Monde and James Legg

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2003
2009
2013
RESEARCH PROBLEM AND CONTEXT
Cassava Staple food and an important source of
income from processed products
Pests: Whiteflies
Diseases : CRND, CMD & CBSD
Highly resilient crop
1936
Threatened by the emergence of new
strains of pathogens
Legg et al. 2013

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This situation shows the increasingly
dwindling cassava production in DRC
over the last decades
Causes:
✓ Inadequate agriculture polices,
✓ Lack of innovative technologies and
equipment;
✓ Persistence of (outdated) traditional
practices;
✓ Insufficiency in funding allocation to
agricultural sector and to agricultural
research;
✓ Soil degradation;
✓ Prevalence of Pests and Diseases
Cassava Production Data

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Determine the spatial and temporal distribution of cassava brown streak
disease (CBSD) in the pandemic-affected areas of Eastern DRC and the
factors influencing its spread
To determine the spatio-
temporal epidemiological
status and molecular
characterization of cassava
brown streak disease in
eastern Democratic
Republic of Congo.
Determine the genetic diversity of the whitefly population in
eastern DRC and its implication on the spread of cassava brown
streak disease.
General objective Specific objectives
Determine the genetic diversity of viruses associated with cassava
brown streak disease in eastern DRC
Correlate CBSD incidence with whitefly abundance and altitude
in epidemic areas of eastern DRC.
Better interconnection of specific objectives for research impact

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RESEARCH AREA
1. Aire De recherche : 461,636 km2
2. Longitude : 24.75°E et 31.66°E
3. Latitude: 3.96°N et 13.94°S
Sampling method
Methogological Approach
Parameters:
1. Incidence
2. Severity
3. Whiteflies Abundance
Samples Collection :
1. Cassava leaves
2. Adult Whiteflies
3. Geographical coordinates
Epidemiological surveillance
was based on previous work:
1. Sseruwagi et al. (2004)
2. Legg et al. (2006)
3. Great Lakes Cassava Initiative
(2009)
4. Maruthi et al. (2005)
5. Jeremiah et al. (2015)
6. Casinga et al. (2018)

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Softwares
GPS Garmin 64s
Ordinateur HP Spectre Agilent Technologies Mx Real-time PCR System
Aspirateur + Eppendorf + pipette
Cool box
Electrophorèse gel system unit
Genogrinder
Centrifugeuse
Pipette set of 4
Equipment Used

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CBSD incidence, CBSD severity and whitefly abundance recorded in the most frequently
occurring (≥ 5 fields) local and improved (I) varieties in eastern DRC

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Incidence and severity of CBSD

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INCIDENCE OF CASSAVA BROWN STREAK DISEASE IN EASTERN DRC

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SPATIAL DISTRIBUTION OF CBSD VIRUS STRAINS

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Nº Provinces Territories
Number
of fields
surveyed
WfAve
CBSDInc
(%)
CBSDSev
(1-5)
Nº Provinces Territories
Number
of fields
surveyed
WfAve
CBSDInc
(%)
CBSDSev
(1-5)
Kambove 4 0 0 1 Kambove 1 0,03 0 1
Kasenga 17 2,09 0 1 Kasenga 5 0,09 0 1
Kipushi 5 0,42 0 1 Kipushi 10 0,06 0 1
Pweto 32 12,75 16,7 2,03 Pweto 17 1,75 52,1 2,97
Sakania 2 0 0 1 Sakania 3 0,05 0 1
Masisi 7 3,68 0 1 Masisi 17 3,49 48,7 2,78
Nyiragongo 1 0,5 0 1 Nyiragongo 3 0,03 36,67 2,18
Rutshuru 4 7,7 48,3 3,32 Rutshuru 9 4,09 59,5 2,86
Fizi 30 4,48 38,1 2,92 Fizi 22 1,15 62,5 3,02
Kabare 7 13,3 0 1 Kabare 18 0,34 16,67 2,6
Uvira 10 36,3 50,02 2,94 Uvira 9 8,94 71,3 3,02
Walungu 5 16 33,3 2,75 Walungu 23 0,44 55,8 2,77
NA NA NA NA NA Idjwi 6 1,18 0 1
NA NA NA NA NA Kalehe 15 1,56 25 2,79
Kalemi 19 0,48 0 1 Kalemi 19 1,41 0 1
Moba 22 3,75 0 1 NA NA NA NA NA
Aru 7 20,21 84,76 3 Aru NA NA NA NA
Djugu 1 0 0 1 Djugu NA NA NA NA
Irumu 7 4,4 0 1 Irumu NA NA NA NA
Mahagi 15 3,57 94,29 3,4 Mahagi NA NA NA NA
Mambasa 6 9,09 0 1 Mambasa NA NA NA NA
Year 2016 Year 2018
1
2
5
3
4
1
2
3
4
5
Haut-Katanga
Nord-Kivu
Sud-Kivu
Tanganyika
Ituri
Haut-Katanga
Nord-Kivu
Sud-Kivu
Tanganyika
Ituri
Legend. WfAve= Moyenne Mouches blanches; CBSD Inc.= Incidence de la maladie de striure brune du manioc; CBSD Sev= Sévérité de la
maladie de striure brune du manioc; NA=Non applicable
Results

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Province Territory CBSD
affected
CBSD free PCR
positive
PCR
negative
Not tested CBSD
affected
CBSD free Not tested qPCR
positive
qPCR
negative
2016 2018
Ituri
Mambasa 0 6 0 6 0 NS NS NS NS NS
Irumu 0 7 0 7 0 NS NS NS NS NS
Mahagi 7 8 8 7 0 NS NS NS NS NS
Aru 5 2 0 0 NS NS NS NS NS
Djugu 0 1 1 0 0 NS NS NS NS NS
Nord-Kivu
Masisi 0 6 0 6 0 5 12 16 1 0
Bweremana 0 1 0 1 0 NS NS NS NS NS
Rutshuru 4 0 4 0 0 7 0 1 6 0
Nyiragongo 0 1 0 1 0 1 4 2 2 1
Sud-Kivu
Kabare 0 7 0 2 5 1 18 4 1 14
Walungu 2 3 2 1 2 7 16 12 5 6
Uvira 9 1 1 0 9 8 1 5 4 0
Fizi 21 9 7 10 13 12 10 13 9 0
Kalehe NS NS NS NS NS 2 13 0 0 15
Idjwi NS NS NS NS NS 0 18 0 0 18
Tanganyika
Kalemie 0 19 0 19 0 0 18 0 0 18
Moba 0 22 0 22 0 NS NS NS NS NS
Haut-Katanga
Pweto 5 27 1 18 13 12 6 2 10 6
Kasenga 0 17 NT NT 17 0 5 0 0 5
Kipushi 0 5 NT NT 5 0 9 0 0 9
Sakania 0 2 NT NT 2 0 3 0 0 3
Kambove 0 4 NT NT 4 0 1 0 0 1
TOTAL 53 148 31 100 70 55 134 55 38 96
Real-time PCR results

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(a) (b)
Phylogenetic analysis of CBSIs in eastern DR Congo

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Major B. tabaci Genetic Groups (Everlyne Wosula and Colleagues)

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Phylogenetic Analysis of B. tabaci COI Sequences – Eastern DRC
Figure 4. Maximum likelihood phylogenetic tree constructed for COI
sequences obtained from Bemisia tabaci collected in eastern Democratic
Republic of Congo between March 2016 and September 2018. GenBank
reference sequences (◆) are included for comparison purposes.
✓ The phylogenetic tree shows six genetic mitotypes of cassava
whiteflies, four of which are designated in the SSA1 group,
namely SSA1-SG1 (74 %), SSA1-SG1/SG2 (2 %), SSA1-SG3 (1
%) et SSA1-SG2 (17 %).
✓ The other major groups are: SSA4 (2 %) et SSA2 (4 %)

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Relationship between mtCOI and SNP identities

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Province
Nombre des
mouches blanches
SNP identité COI identité
Ituri, Sud-Kivu and Nord-Kivu 51 SSA-ECA SG1-a
Haut-Katanga, Sud Kivu 2 SSA-ECA SG1-b
Ituri, Sud-Kivu and Nord-Kivu 15 SSA-ECA SG2-a
Sud-Kivu 2 SSA-ECA SG1-SG2
Sud-Kivu 1 SSA-ECA SSA4
Haut-Katanga 1 SSA-ECA/CA SG1-b
Sud-Kivu 1 SSA-CA SG1-a
Haut-Katanga 19 SSA-CA SG1-b
Tanganyika 1 SSA-CA SG2-a
Haut-Katanga 1 SSA-CA SG2-b
Haut-Katanga 1 SSA-ESA SSA1-SG3
Sud-Kivu 1 SSA-ESA SSA4
Ituri 4 SSA2 SSA2
Relationship between province of origin information and SNP identities
Number of Whitefly SNP Identity COI Identity

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Genetic diversity of B. afer colonizing cassava in eastern DRC

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Cassava disease related constraints in DR Congo

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CONCLUSION
All improved and local cassava varieties being released in the research area are
susceptible to cassava brown streak disease in all affected provinces.
The correlation between CBSD incidence and whitefly abundance with altitude is
negative.
The overall level of congruence between field incidence of CBSD and PCR diagnostic
results was 90.8% in 2016 and 89.6% in 2018.
CBSD is clearly expanding from East to West DRC. In Haut-Katanga where it has
increased from 16.7% incidence in 2016 to 52.1% in 2018.
CBSV and UCBSV strains are associated with CBSD. Cases of mixed infection are present
in Mahagi territory in Ituri province.
Genetic diversity confirms the existence of two major groups of Bemisia afer in DRC.
KASP genotyping revealed the existence of three haplogroups of B. tabaci of which SSA-
ECA is the most common (73%), followed by SSA-CA (23%) and SSA2 (4%).

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THANKS TO