Molecular biology of plant virus-host and virus-vector interactions

Aims: To understand the role and function of virus encoded proteins and their interactions in the pathogenicity and spread of plant virus diseases.

Background: Potato is an important crop in Scotland with around about 1.3 million tonnes of potatoes produced and 76,000 tonnes of seed exported to over 30 countries (outside the EU). Pests and diseases are a major constraint to the industry causing economic losses by decreased tuber yield and quality, and rejection of exports.

Soil-borne potato mop-top virus (PMTV) and aphid transmitted potyviruses (principally PVY) are economically important problems in potato seed crops that are difficult to control. No sources of resistance to PMTV have been identified in Solanum tuberosum and there are no reliable methods to control the spread of PMTV by the soil-borne plasmodiophorid vector Spongospora subterranea (that also causes powdery scab disease on potato tubers).

In addition, the application of insecticides to control the spread of aphid-borne potato potyviruses such as PVY is not effective. It is expected that aphid populations may build up earlier in the season and aphid-borne virus spread may increase because of the warmer temperatures predicted with environmental change.

Studying the molecular interactions between virus-host and virus-vector will provide a deeper understanding of the mechanisms of virus transmission and host resistance. The practical outputs of the work will be to identify new sources of resistance and more effective methods of disease control.

Current focus: Investigating a novel resistance to PVY (and other potyviruses) that we have discovered in Solanum tuberosum Group Phureja germplasm; the effect of heat stress on virus resistance and the molecular basis of mature plant resistance in potato.

Studies on the localisation and function of PMTV TGB movement proteins have revealed that PMTV infection includes a nuclear/nucleolar phase important for long distance movement in the vascular system and that the movement protein TGB1 determines nucleolar targeting and we are investigating a host factor that mediates nuclear association. In vitro culture of potato 'hairy root' systems have been established to investigate the molecular mechanism of vector transmission of PMTV.

Other research in the lab concerns working with partners in Africa to improve seed potato production systems and collaboration with Ziejiang Academy of Agricultural Sciences on soil-borne viruses.

News

Potato research meeting in Kenya

A meeting funded by a BBSRC GCRF Impact accelerator accounts award to the University of St Andrews was held in Nairobi on 11 November. The meeting highlighted recent research findings from predominantly BBSRC and RESAS funded research on virus resistance, heat tolerance and early maturity conducted by Mark Taylor, Lesley Torrance, Alison Roberts, Glenn Bryan and colleagues.

Delegates also heard about potato varieties suited to Kenyan growing conditions including varieties developed by James Hutton Ltd in collaborative breeding contracts. The meeting allowed networking of researchers, plant health officials, potato growers and industry with discussions on the needs of Kenyan potato farmers.

New collaboration 

NSF/BBSRC Project on The spatial epidemiology of a vector-borne plant virus (PVY) with partners in USA led by Professor A Power, University of Cornell.

New developments

The potato cultivar Mayan Gold has passed national Perfomance Trials in Kenya and is approved for distribution to farmers. Mayan Gold has excellent properties that are beneficial for small holder rural farmers including PVY resistance, fast cooking time, good fry quality and good taste.

Our paper on distribution of pests and diseases in Kenyan potato growing regions has been published in Potato Research: Occurrence and distribution of potato pests and diseases in Kenya.

Strengthening Potato Production in SSA; Malawi and Kenya

Malawi: Working with partners Paul Demo, CIP potato seed specialist, Malawi and Felistus Chipungu, Department Agriculture Research Services, Bvumbwe Research Station.

This Scottish Government supported project aims to contribute to poverty reduction and food security through strengthening the development of sustainable potato production and marketing systems for improved productivity and trade. The main achievements to date are in renovation and upgrading facilities for mini tuber production, the introduction and evaluation of new cultivars and capacity building.

In collaboration with DARS, CIP and SASA, Edinburgh we delivered a training course in seed potato crop inspection, disease identification, and diagnostic in Dedza District of Malawi, 13–16 March 2012. Lesley Torrance and two senior potato seed inspectors (John Ellicott and Maureen McCreath) travelled from Scotland to Malawi for the training.

The course had 37 trainees from different organisations in Malawi involved in seed quality control, seed production, or in backstopping farmers. We conducted classroom and field work and surveyed local farmers’ fields. This year was a bad one for late blight with many crops destroyed or badly affected. Potato crops were also affected by PVY and bacterial wilt. We found recombinant strains of PVY in potato crops.

Scottish Government Funded Potato Project, Training Course, Near Dedza Pottery, Malawi, March 2012 from eric monaghan on Vimeo.

Kenya: The project is supported by The Monsanto Fund and we are working with partners Dr Hassan Were (Masinde Muliro University of Science and Technology, Kakamega), Dr J. Kabira, KARI Tigoni and Professor F. Olubayo (University of Nairobi).

The main outcomes of this project are:

• A comprehensive pest and disease survey in all five major potato producing areas in Kenya.
• Identification of areas of low aphid pressure for seed tuber multiplication.
• Introduction of tissue culture microplants of 12 cultivars with different agronomic qualities to KARI Tigoni who have bulked up the material.  

All introduced cultivars are growing well in the region. Sufficient material of three cultivars has been submitted for National Performance Trials and we are collaborating with the Kenyan National Potato Council to disseminate information and demonstrate the qualities of the new material in field trials.