The Plant Diseases research group develops and uses diagnostic technology for fungi, bacteria and viruses that cause diseases in root crops, vegetables and cereals. These tools are used to investigate the epidemiology of economically-damaging plant pathogens and understand how they interact with their vectors to drive epidemics. The mix of molecular and whole-organism expertise is essential for tackling complex problems, particularly when these involve different arthropod vector populations that cannot be differentiated by conventional taxonomic techniques. This broad range of expertise has not only facilitated fundamental understanding of the mechanisms involved in the spread of plant diseases, but has also enabled the development of several highly successful disease-management technologies. Collaborative links range from international institutes, companies and universities in UK, India and Africa, to local farmers’ groups and non-governmental organizations.

Achievements

Major recent achievements include the first reports that two economically important pathosystems share a key mechanism that drives epidemics. The viruses involved share a mutually beneficial relationship with their whitefly vector, Bemisia tabaci, where a greater population growth rate occurs among vectors feeding on virus-infected compared to healthy plants. The viruses and Bemisia tabaci populations that spread these epidemics are also co-adapted, which maximizes virus transmission efficacy and allows even low numbers of B. tabaci adults to spread viral disease highly effectively. These relationships emphasize the need for host-plant viral resistance as a key component of strategies designed to manage these problems. The team has also been successful in identifying new virus isolates and vector populations. Since 2001, >200 nucleotide and protein sequence entries have been deposited in gene banks (EMBL, NCBI and DDBJ).

 

Other research has led to important discoveries of different isolates of Cassava brown streak virus, a disease that is expanding its range in East Africa and has recently re-emerged in Uganda. This disease’s vector has also been identified for the first time as B. tabaci. Cassava varieties resistant to Cassava mosaic virus have been disseminated widely in Africa to counteract the effects of the cassava mosaic disease pandemic and control strategies were developed for sweet-potato viral diseases in Africa. Participatory plant-breeding approaches were developed and validated for the first time for cassava and sweet potato, leading to the identification of high-yielding disease-resistant cultivars that have been adopted readily by farmers.

 

The evolutionary response of plant viruses to host-plant resistance is an important research area. Molecular markers were developed successfully to identify resistance to the aphid vector of groundnut rosette disease. Survey work to identify the severity of economically-damaging coffee diseases has highlighted this threat to coffee production in Malawi.

Future Plans

The team’s strategy is to continue to meet the challenges presented by emerging plant-disease epidemics, and funding is currently available for working with the private sector in India to develop tomato leaf curl resistant hybrids. Funding is also being sought to study B. tabaci in the UK, as it may become an established outdoor threat with climate change. International linkages with CGIAR centres and European institutions will continue through multi-disciplinary projects on transgenic disease-resistant cassava and sweet potato.

Staff

Dr Tim Chancellor
Prof John Colvin
Dr Richard Gibson
Dr Rory Hillocks
Dr James Legg
Dr M N Maruthi
Dr Sue Seal

Recent Publications

Alicai, T., Omongo, C.A., Maruthi, M.N., Hillocks, R.J., Baguma, Y., Kawuki, R., Bua, A., Otim-Nape, G.W. & Colvin, J. (2007) Re-emergence of Cassava Brown Streak Disease in Uganda. Plant Disease 91: 24-29.

Aswatha Narayana DS, Rangaswamy KT, Shankarappa KS, Maruthi MN, Lakshminarayana Reddy CN, Rekha AR, Keshava Murthy KV. (2007). Distinct begomoviruses closely related to cassava mosaic viruses cause Indian Jatropha mosaic disease. International Journal of Virology (In press).

Gibson, R.W., Byamukama, E., Mpembe, I., Kayongo, J., Mwanga, R. O. M. (2007). Working with farmer groups in Uganda to develop new sweet potato cultivars: decentralisation and building on traditional approaches. Euphytica (Accepted)

Maruthi MN, Rekha AR, Muniyappa V. (2007). Pumpkin yellow vein mosaic disease is caused by two distinct begomoviruses; complete viral sequences and comparative transmission by an indigenous and B-biotype Bemisia tabaci. EPPO Bulletin (In press).

Maruthi MN, Rekha AR, Sseruwagi P, Hillocks RJ. (2007). Mitochondrial DNA variability and development of a PCR diagnostic test for Bemisia afer (Priesner & Hosny) populations. Molecular Biotechnology (In press).

Shankarappa KS, Rangaswamy KT, Raghavendra N, Rekha AR, Aswatha Narayana DS, Lakshminarayana Reddy CN, Chancellor TCB, Maruthi MN, (2007). Development of silverleaf assay, protein and nucleic acid based diagnostic techniques for quick and reliable detection and monitoring biotype B of the whitefly, Bemisia tabaci (Gennadius). Bulletin of Entomological Research (In press).

Robinson, E.Z., Rani Das, S. and Chancellor, T.C.B. (2007) 'Farmer decision making in rice pest management in Bangladesh'. Agriculture and Human Values 24(3): xx-xx.