BREEDING STRATEGIES FOR CONTROLLING THE PANDEMIC OF CASSAVA MOSAIC VIRUS DISEASE IN EAST AND CENTRAL

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BREEDING STRATEGIES FOR CONTROLLING THE PANDEMIC
OF CASSAVA MOSAIC VIRUS DISEASE IN EAST AND
CENTRAL AFRICABill W. Khizzah, J. B. A
Whyte, A. Dixon and H. Ojulong
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Importance of cassava The largest single source
of dietary energy for over 200million
people Leaves are extensively used as vegetable
(protein, vitamins, minerals Generates cash
income for a large number of households
(COSCA). Essential contributor to food security,
poverty alleviation and economic growth   Huge
yield losses are attributed to a number of biotic
and abiotic stresses. CMD 15 24 of the
potential production, approx. 1,200-2,300
million/year in SSA.
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1990s, an epidemic of CMD reported in north
central Uganda expanded to cover the whole
country with extension to Kenya, Tanzania, D R
Congo and Rwanda.   Yield losses in sensitive
local cultivar was so great that farmers
abandoned cassava cultivation.   Localised food
shortages that led to famine-related
deaths.   Pyhtosanitary measure (clean planting
material and rouging of the infected plants) was
not effective.   Dployment of host plant
resistance the only long term and sustainable
way.  
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The CMD epidemic 1990s, an epidemic of CMD
reported in north central Uganda expanded to
cover the whole country with extension to Kenya,
Tanzania, D R Congo and Rwanda.   Yield losses in
sensitive local cultivar was so great that
farmers abandoned cassava cultivation.   Localised
food shortages that led to famine-related
deaths.   Pyhtosanitary measure (clean planting
material and rouging of the infected plants) was
not effective.   Deployment of host plant
resistance the only long term and sustainable
way.  
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Use of African landraces   Identification of
Ubiaja (Nigeria) in 1989 permitted IITA to use
the African landraces maintained at the genetic
resource division to improve resistance to CMD,
broadened the genetic resource base of the
breeding populations while retaining the African
adapted gene-pool The program emphasised
resistance CGM, storage root quality, branching
habit, and foliage quality. Made available
breeding materials that could be used directly as
varieties or improved seed populations.
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Building upon these achievements, EARRNET
incorporated new objectives and approaches that
addresses the mkt. oriented RD strategies of
ASARECA considering The supply of improved
seeds and populations Experience gained by the
Uganda National Root Crop Program ( in
multiplication and distribution of improved
varieties and on CMD) The findings of COSCA
which provided quantified information on cassava
as a major food crop   The cassava mosaic
diagnostics protocols that allowed the Uganda
cassava mosaic variant (UgV) to be distinguished
from both ACMV and EACMV.  
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• Sourcing from these broad base populations, the
  network in collaboration with NARO initiated a
  germplasm enhancement program at SAARI to cater
  for mid altitude medium rainfall ecology to.
•  
• Generate disease and pest resistant and adapted
  populations with high stable yields and desired
  characteristics for agro-ecology targeting
  different end uses/markets.
•  
• Avail the populations to network member countries
  for evaluation and selection under specific
  agro-ecosystems.
• Establish special backup populations.

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Figure 1 A five-stage selection and evaluation
scheme for cassava   Stage 1 Resistance to
biotic stresses, high yield/dry matter with
appropriate root quality, low cyanogenic
potential and desired agronomic characters.
Stage 2 Application of different levels of
inputs to target commercial and subsistence
growers. Stage 3 Biochemical and physical
profiles of each improved clones to satisfy
different end user markets.   Stage 4 Parental
identification/selection. Development of special
populations for use in breeding programs.  
Stage 5 Distribution to NARS in collaboration
wit networks.
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Germplasm distribution Biggest constraint was the
availability and supply of CMD resistant planting
materials. the safe movement cassava germplasm
as seeds, pathogen-tested, in vitro material or
in vitro material that has been grown under
containment (FAO/IBPGR) . Screening for local
adaptability and end user preference takes
several years Lack of local capacity in tissue
culture handling, failure rates can be high.
Open quarantine sites 1997 establishment of
open quarantine sites (Alupe and Karama) opened a
new chapter in regional germplasm movement
history.
.  
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The facilities permitted a fast-track
introduction of improved clones form the
regional improvement program in Serere for one
year observation by quarantine official before
release to national programs for further
evaluation and release to farmers. The clones
after release formed the basis of multi location
evaluation, and multiplication in W Kenya In
Rwanda, they provided the source of improved
clones for D R Congo and Burundi Overall,
broadened the genetic base of cassava in these
countries and provided new route for germplasm
exchange.
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On-farm evaluation Farmer participatory on-farm
evaluation initiated using augmented design
(Uganda and Kenya involving over 300 farmers and
about 40 clones) Facilitate researcher-farmer
collaboration, farmer participation and ensure
quick assessment of a large number of improved
clones Preliminary results indicate over 90
shown no cassava mosaic disease symptoms. From
farmers perspectives, large number of improved
varieties will provide for their diverse food
needs and a buffer against major cassava pests
and diseases. Enabling identification of
genotypes with wide adaptation
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farmer participatory on-farm evaluation
initiated using augmented design (Uganda and
Kenya involving over 300 farmers and about 40
clones) facilitated researcher-farmer
collaboration, farmer participation and ensured
quick assessment of a large number of improved
clones results indicate over 90 shown no
cassava mosaic disease symptoms. farmers
perspectives, diverse food needs and buffered
against major cassava pests and diseases.
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Screening and multi-location trials
Farmer participatory evaluation
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Improved varieties released to farmers
Fresh and dry cassava sold to urban as well as
local markets
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Future spread of the pandemic Monitoring
surveys have guided germplasm distribution   In
Uganda use of improved varieties shifted from 17
in 1998 to 35 in 2001   CMD incidence reduced
from 76 to 66   Yield increased by 218,466t over
1998 level (US 21.9 million) Rate of the
pandemic spread will depend on rate of deployment
of improved clones, acceptance and utilization by
farmers of resistant clones.    
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Acknowledge the financial contributions from our
major donors USAID PL-480, OFDA, The Rockefeller
Foundation, The Gatsby Charitable Organization
(UK) and IITA technical backstopping. Thank you
for Listening    
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