Strategies for managing groundnut rosette disease in Sub-Saharan Africa
Strategies for Managing Groundnut Rosette
Disease in Sub-Saharan Africa
Sep 2010
Introduction
Groundnut rosette disease (GRD) is the single most destructive disease
affecting the production of groundnuts in Africa causing losses estimated
at $156 million each year.Epidemics frequently result in yield losses
approaching 100% in many fields and recurrent epidemics,associated with
significant economic losses,have been reported in many African countries.
GRD etiology
GRD,which only occurs in Africa is caused by a complex of three agents –
• groundnut rosette umbravirus (GRV),
• its satellite RNA (Sat RNA),and
• phloem-limited groundnut rosette assistor luteovirus (GRAV).
All the three disease agents must be present in the host plant for aphid
(Aphis craccivora Koch) transmission to occur.GRV alone is mechanically
transmissible.GRV and GRAV alone show no obvious symptoms.In other
words,the various forms of Sat RNA are responsible for the various
symptoms of GRD.
GRD management
1. Pesticide application to reduce aphid vector population. Chemicals
can control aphids,but resource-poor farmers often cannot afford them
and/or they are not available.Use of chemicals raises environmental and
health risks/concerns.
2. Cropping practices to delay onset and spread of the disease. Early
sowing (aphids prefer younger,more succulent crops) and achieving
denser plant populations (aphids preferentially alight on widely spaced
plants and move more easily) have also been shown to provide effective
GRD control.However,these and other practices,such as removal of off-
season volunteer plants and ground keepers,are poorly adopted by
small-scale farmers.
3. Breeding for virus and vector resistance. Use of resistant varieties has
been the most effective strategy for control of GRD in sub-Saharan Africa.
ICRISAT and partners have made available high-yielding,short-,medium-
and long- duration genotypes with good levels of resistance to GRD for
the different eastern and southern Africa agroecologies.
Key successes in breeding for resistance to GRD
ICRISAT and partners have:
• supplied more than 8000 germplasm lines to various countries in Africa
for evaluation and utilization.
• screened over 12,500 germplasm lines,including 116 wild Arachis species,
for rosette resistance and identified 130 long-duration and 20 short-
duration materials with resistance to GRD.
• transferred GRD resistance from longer duration (Virginia types) to
shorter duration (Spanish) germplasm necessary for areas with shorter
rainfall patterns.
• identified immunity to GRAV from wild groundnut germplasm.
• confirmed that resistance to GRD is governed by two independent
recessive genes.
• confirmed two sources of resistance to GRD – ICGV-SM 90704 resistant
to GRV but susceptible to aphids and ICG 12991 resistant to aphids but
susceptible to GRV.
• facilitated release of six rosette resistant varieties in the last five years.
These germplasm are now being used by thousands of farmers in Malawi,
Mozambique,South Africa,Tanzania,Uganda,Zambia,and Zimbabwe.
• disseminated GRD management technologies to farmers through
participatory on-farm trials with farmer organizations.
Future strategies
1. Combine multiple disease resistances (e.g.,rosette and ELS),in early
maturity backgrounds to further improve crop productivity and
adaptation to the African semi-arid tropics
2. Understand the off-season survival of the GRD virus complex and identify
indigenous host(s)
3. Identify more sources of resistance to GRD
4. Combine resistance to all three virus complex factors (GRV,GRAV,Sat
RNA) and resistance to the aphid vector
5. Explore use of molecular markers to obtain faster/simpler screening
techniques
Screening for rosette resistance using the infector row technique at
ICRISAT-Lilongwe.
Rosette damage to groundnut.