Groundnut rosette disease management

Groundnuts are a key crop in eastern Uganda, grown for both food and income. The major factor limiting production is groundnut rosette disease, a virus disease transmitted by aphids. This project built on previous CPP epidemiological research in Malawi which identified new sources of resistance to aphids and to rosette disease. Screening methodologies were developed to enhance the efficiency of groundnut improvement programmes. Working closely with researchers, agricultural extension agents, NGOs and farmers, the project’s ultimate aim was to to develop sustainable management strategies for groundnut rosette disease, based primarily on the use of improved groundnut varieties with durable resistance to pests and diseases. The availability of new, short-duration, disease-resistant groundnut varieties will assist a substantial number of smallholder farmers to increase their incom

The nature of the resistance in groundnut to rosette disease

Groundnut rosette disease is caused by a complex of three agents, groundnut rosette virus (GRV) and its satellite RNA, and groundnut rosette assistor virus (GRAV); the satellite RNA is mainly responsible for the disease symptoms. Groundnut genotypes possessing resistance to rosette disease were shown to be highly resistant (though not immune) to GRV and therefore to its satellite RNA, but were fully susceptible to GRAV

Groundnut viral diseases in West Africa

This paper describes groundnut viral diseases observed in West Africa. Six viruses are identified and their main properties are reported here: peanut Clump, groundnut rosette, groundnut eyespot, groundnut crinkle, tomato spotted wilt and groundnut chlorotic spotting viruses. Four other diseases are described in part: groundnut streak, groundnut mosaic, groundnut flecking and groundnut golden mosaic diseases. Some of them are economically very important such as the two strains of rosette, peanut clump and tomato spotted wilt diseases. Others are apparently of minor importance though they occur relatively frequently and show a wide distribution, such as groundnut eyespot, groundnut crinkle, groundnut streak and groundnut golden mosaic diseases. The others appear occasionally but are nevertheless described: some which are very infectious, as groundnut chlorotic spotting disease could become very important within a few years. (Résumé d'auteur

A Century of Research on Groundnut Rosette Disease and its Management. Information Bulletin no. 75

Groundnut rosette is a major disease of groundnut (Arachis hypogaea L.) endemic to sub-Saharan Africa. The disease is restricted to the African continent and its offshore islands. It is responsible for annual groundnut yield loss worth over US$150 million. A complex of three agents is involved in rosette disease etiology: Groundnut rosette assistor virus (GRAV; Family, Luteoviridae), Groundnut rosette virus (GRV; Genus, Umbravirus) and a Satellite-RNA (SatRNA) associated with GRV. The disease is spread in nature by the aphid vector, Aphis craccivora Koch, and occurs in two predominant symptom forms, chlorotic rosette and green rosette. Past research has revealed that SatRNA is responsible for rosette disease symptoms. GRAV or GRV on their own cause mild mottle symptoms. GRV functions as helper for SatRNA replication, whereas GRAV functions as helper virus in vector transmission of GRV and SatRNA. Through over 30 years research experience on this disease, the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) and its partners have made significant contributions towards the understanding of rosette disease etiology, molecular characterization, virus-vector interactions and development of serological (enzyme-linked immunosorbent assay) and nucleic acid (dot-blot hybridization and reverse transcription-polymerase chain reaction) based diagnostic assays. This knowledge has provided basis for development and utilization of groundnut cultivars with resistance to the groundnut rosette disease and impacted the lives of thousands of farmers in sub-Saharan Africa. This information bulletin provides an overview of the groundnut rosette disease, properties of the etiological agents, protocols for their detection, information on screening groundnut germplasm for resistance to the disease and resistant sources, and various management option

Farmer perceptions and genetic studies of rosette disease in groundnut (Arachis hypogaea L.) in northern Mozambique.

Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.Groundnut (Arachis hypogaea L.) is an important food and cash crop in Mozambique and production has been constrained by lack of high-yielding cultivars and disease infection. Objectives of this study were: 1) to identify farmers’ major groundnut production constraints and their preferences for cultivars; 2) to determine genotypic variation among landraces for agro-morphological traits and resistance to groundnut rosette disease; 3) to determine agronomic performance and resistance to groundnut rosette disease among advanced groundnut lines; and 4) to determine the inheritance of resistance to groundnut rosette disease. The study was conducted in northern Mozambique from 2008/2009 to 2010/2011. In attempt to identify farmers’ major groundnut production constraints and their preferences in cultivars, a participatory rural appraisal (PRA) was conducted in Namuno and Erati districts in northern Mozambique. Results from the PRA showed that farmers were aware of the constraints affecting groundnut production and productivity in the study area. The major constraints included groundnut rosette disease, insect pests, lack of seeds and improved cultivars, low soil fertility and lack of infra-structure. Groundnut rosette disease was ranked the most important constraint, and it was widespread in the region. Selection criterion for groundnut cultivars used by women differed from that used by men within village and across villages. However, high yield and oil content were the most important traits preferred by farmers followed by pod and seed size, earliness, disease and insect pest resistance. Fifty-eight groundnut landraces were collected from northern Mozambique (Nampula, Cabo Delgado, Niassa and Zambezia) and evaluated for variation in agro-morphological traits and resistance to groundnut rosette disease. The landraces showed high phenotypic diversity in agro-morphological traits. Clustering by nearest neighbour method indicated that the genotypes could be grouped into six clusters, indicating that agro-morphological diversity exists. The highest yielding genotypes were Pambara-4, Pambara-2, Pambara-6, lle-1, Imponge-1-Tom and Gile-5. There was considerable genetic variability for resistance to groundnut rosette disease among the landraces. Four landraces (PAN-4, Imponge-4, Pambara-3, Metarica Joao) were classified as resistant. No significant correlation was observed between seed yield and groundnut rosette incidence. Thirty-two improved lines were evaluated for performance in two growing seasons across three locations in northern Mozambique (Nampula, Namapa and Mapupulo). The results indicated that the highest yielding genotype was 23A and the highest yielding location was Namapa. There was a significant and negative correlation between seed yield and groundnut rosette disease indicating that the seed yield was negatively influenced by the disease. The results on stability analysis indicated that genotype 35B was the most stable across environments since it had coefficient of regression around unity (bi=1.024), high coefficient of determination (R2=0.999), and small variance deviation (var-dev=162.8), and 13 % above average seed yield. It is, therefore, concluded that genotype 35A could be recommended for cultivation on diverse environments of northern Mozambique. A trial was conducted using the parents and F2 populations derived from a 7 X 7 diallel cross. The test materials were infected with groundnut rosette disease using the spreader-row technique. The results indicated that no genotype was immune to disease. The mean squares due to both general combining ability (GCA) and specific combining ability (SCA) were significant indicating that additive and non-additive gene actions were involved in the expression of resistance to groundnut rosette disease. The general predictability ratio (GCA:SCA) was 0.97, indicating the predominance of additive over non-additive gene action in the inheritance of the disease. The study also found that groundnut rosette disease was controlled by two recessive genes. However, some genetic modifiers may also be present and influence disease expression. In general, the study revealed that breeding opportunities do exist, incorporating farmers preferred traits and major groundnut production constraints into new groundnut cultivars. Improving cultivars for resistance to groundnut rosette disease will be a major breeding focus, while selection for other traits and constraints will not be ignored. Resistance has been identified from local landraces. Advanced lines with high yields across environments were identified that can be recommended for release. The high significant additive effects observed for groundnut rosette disease implied genetic advance could be effective in the F2 and later generations through selection, although modifiers could slow the progress

Registration of ICG 12991 peanut germplasm line

ICG 12991 is a short duration (90–110 d to maturation), drought-tolerant, spanish-type peanut (Arachis hypogaea L. subsp. fastigiata Waldron var. vulgaris Harz.) germplasm line (Reg. no. GP-122, PI 639691) with a high level of field resistance to groundnut rosette disease (Naidu et al., 1999a; Subrahmanyam et al., 2000). Groundnut rosette disease results from a synergism of three agents: Groundnut rosette assistor virus (GRAV, a luteovirus), Groundnut rosette virus (GRV, an umbravirus), and a satellite RNA (sat RNA) of GRV. ICG 12991 was originally collected from a farmer’s field in south India in 1988. In 1994, ICRISAT introduced ICG 12991 into Malawi for evaluation during a germplasm screening program for resistance to groundnut rosette disease and early leaf spot disease (caused by Cercospora arachidicola S. Hori). Subsequently, ICG 12991 was released in Malawi as ‘Baka’ in 2001 and in Uganda as ‘Serenut 4T’ in 2002, following extensive testing and distribution by the national programs of each country. Resistance to groundnut rosette disease in ICG 12991 is due to aphid resistance, not due to resistance to the virus complex (Naidu et al., 1999b)

Groundnut Virus Diseases in Africa Incorporating the Proceedings of the Fourth Meeting of the Consultative Group on Collaborative Research on Groundnut Rosette Virus Disease

Groundnuts are an important oilseeds crop in many African countries. And groundnut rosette is the most important virus disease of groundnut in Africa. An International Working Group was established in 1983 to formulate cooperative research programs to characterize the causal viruses of groundnut rosette disease and develop methods for their detection. The group met in 1985 in Cambridge, England, and in 1987 in Lilongwe, Malawi. Since the efforts by this Group have resulted in considerable progress on the characterization of causal viruses of groundnut rosette disease and at the meeting held at Lilongwe, it was suggested that the Group activities should be expanded to include research on all groundnut viruses in Africa. In this publication summaries of the papers delivered at the Group's fourth meeting are presented. The first part deals exclusively with the collaborative research on groundnu t rosette virus disease. In Part 2 four technical papers cover the management of groundnut virus diseases, virus disease surveys, and seed-borne legume viruses. And scientists from Africa review research and the country-specific situations of roundnut virus diseases in Burkina Faso, Congo, Cote d'lvoire, Niger, Senegal, and Sudan. Recommendations are made for further action on global cooperative research on groundnut virus diseases and future research activities, including their priorities, on groundnut viruses in Africa

THE ECONOMIC IMPACT OF PEANUT RESEARCH ON POVERTY REDUCTION: RESISTANCE STRATEGIES TO CONTROL PEANUT VIRUSES IN UGANDA

Economic impacts of research that developed Rosette Virus-resistance peanut in Uganda are estimated. Changes in economic surplus are calculated and combined with household data to assess changes in poverty rates and effects on livelihoods of the poor. The poverty rate may decline up to 1.5 percent as a result of the research.Research and Development/Tech Change/Emerging Technologies,

Spatiotemporal Separation of Groundnut Rosette Disease Agents

Analysis by triple-antibody sandwich enzyme-linked immunosorbent assay of groundnut samples from fields in two seasons from different regions of Malawi showed the absence of groundnut rosette assistor virus (GRAV) from some plants showing groundnut rosette disease symptoms and the presence of GRAV in some symptomless plants. Viruliferous Aphis craccivora collected from fields transmitted either GRAV alone, groundnut rosette virus (GRV) with its satellite RNA (sat RNA), or all three agents together, in different proportions. More plants became infected with all three agents when increasing numbers of potentially viruliferous aphids were used per plant, suggesting a dosage response. Electrical penetration graph studies of aphid stylet activities indicated successful transmission of GRV and its sat RNA during both the "stylet pathway phase" and salivation into sieve elements, whereas GRAV was transmitted only during the latter phase. Aphids transmitted all three agents together only during the salivation phase. Reverse-transcriptase polymerase chain reaction testing of viruliferous aphids and of inoculated plants revealed no correlation between the presence of all three agents in prospective aphid vectors and their simultaneous transmission to groundnut plants. These results show that separation of the groundnut rosette disease agents occurs over time and space