Groundnut rosette disease (GRD), caused by a complex of three agents: groundnut rosette assistor luteovirus, groundnut rosette umbravirus. It depends on groundnut rosette assistor virus (GRAV; Luteoviridae) for encapsidation in GRAV coat protein and for transmission by Aphis craccivora in the. SUMMARY: Groundnut rosette disease is the most important disease of groundnuts of sub-. Saharan Africa. Epidemics occur without warning. It is caused by a.
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Rosette is the most destructive disease of groundnut in Africa. The disease is endemic to sub-Saharan Africa and its off-shore islands, including Madagascar. Two main forms of the disease, chlorotic rosette and green rosette have been described based on symptoms.
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The disease is caused by a complex of three agents: The groundnut aphid, Aphis craccivorais the principal vector of the disease. Rosette disease has been and continues to be responsible for devastating losses to groundnut production in Africa.
For example, the rosette epidemic in in central Malawi and eastern Zambia destroyed the crop to such an extent that the total area of groundnut grown in Malawi fell from 92, ha in to 65, ha in Management of groundnut rosette by rosdtte control of the vector has been known since the mids. Cultural practices such as early sowing at optimal plant densities are known to reduce the disease incidence.
MANAGEMENT OF GROUNDNUT ROSETTE: PAST, PRESENT, AND FUTURE
However, smallholder farmers in Africa for a number of reasons, seldom adopted these practices. Therefore host-plant resistance to the disease and its vector is regarded as the most viable and sustainable solution.
Sources of resistance to rosette were first discovered in Senegal in These sources formed the basis for rosette grooundnut breeding programs throughout Africa and have contributed to the development of several high-yielding, rosette-resistant groundnut varieties e.
However, most of the rosette-resistant varieties released to date are late maturing and are not suitable to some production systems in Africa where the rainy season is short.
ICRISAT scientists developed a simple and effective field screening technique to evaluate germplasm and breeding lines for resistance to rosette.
The sources of resistance from West Africa have extensively been used and several long-duration, high-yielding breeding lines with resistance to rosette have been developed for evaluation and utilization by the National Agricultural Research Systems in the region. Inheritance of rosette resistance in groundnut was confirmed. Rosett and specific methods to detect the three components of rosette disease have been developed.
In spite of several achievements made in the past, development of short-duration groundnut varieties with resistance to rosette remained as a challenge to ICRISAT for a long time. InICRISAT-Lilongwe launched a program rosehte screening of global germplasm for resistance against rosette in order to diversify the genetic base of rosette resistance.
To date, about 12, germplasm lines have been screened and in excess long-duration virginia types and 20 short-duration Spanish types with resistance to rosette have been identified. Resistance to rosette was identified for the first time in Asian and South American land races.
Identification of rosette resistance in Spanish types has great significance to the development of high-yielding short-duration rosette-resistant varieties. ICRISAT scientists continued to develop high-yielding, long-duration groundnut varieties with resistance to rosette suitable to medium and high rainfall areas.
Several of these varieties had excellent performance in farmer participatory on-farm verification in Malawi, Zambia, Mozambique, and Uganda. Recently, several high-yielding short-duration days Spanish types with resistance to rosette have been developed and are in on-farm evaluation in southern and eastern Africa.
High degree of resistance to rosette or its vector was recently identified in wild Arachis species. Components rosettte integrated management of rosette using high-yielding rosette-resistant varieties ICGV-SM and ICG and cultural practices such as early sowing at optimum plant densities have been investigated.
A package of options has been developed and is being verified on-farm in three agroecologies in Malawi.
Current knowledge on epidemiology of groundnut rosette is very scanty to form the basis for disease forecasting and designing comprehensive disease management strategies or explain the sporadic epidemics of the disease. Hence, there is a need to understand the factors that influence rosette disease outbreaks such as off-season survival of rosette viruses, the relative importance of primary and secondary spread, feeding behavior and transmission efficiency of vector, influence of climatic conditions on vector build-up and dispersal.
The sources of resistance identified in global germplasm need to be characterized based on DNA profile and using molecular markers. Utilization of wider gene pools should result diseasse identification of certain cross combinations with high recovery of disease resistance and more useful recombinants. This will also be useful in establishing troundnut allelic relationships.
Mechanisms of resistance operating against individual causal agents of the disease complex and the vector need to be understood. On-farm verification and demonstration of agronomically and commercially acceptable high-yielding, rosette-resistant medium- to short-duration groundnut varieties and the package of options for integrated management of groundnut rosette needs to be intensified in the region. Breeding for multiple resistance rosette virus complex and the vector should receive high priority.