Potato is the third most important food crop in the world after rice and wheat. Potato virus Y (PVY) is one of the most common viruses in potato in all potato-growing areas. It causes serious problems in production and quality of potatoes. We also study viruses infecting raspberries that have been very poorly characterized. For example, we characterize the variability of raspberry leaf blotch virus, black raspberry necrosis virus, rubus yellow net virus and raspberry vein clearing virus.

Sweetpotato production ranks the fifth among food crops in developing countries. China is the biggest producer in the world, but East Africa and the countries surrounding Lake Victoria rank the second, Uganda being the biggest producer there. Sweetpotatoes perform well in rather poor soils and are drought-tolerant, making them a crucial subsistence and famine-relief crop. The most harmful diseases in sweet potatoes (Ipomoea batatas) are viruses. They spread by the cultivation practices and lack of resistant cultivars. Sweet potato chlorotic stunt virus (SPCSV) breaks down the resistance of sweetpotatoes to viruses following infection by other viruses. It results in the severe sweetpotato virus disease (SPVD) and high or complete yield losses. We study the mechanisms by which SPCSV synergizes with other viruses.

The aim of this research programme is to reveal how plants defend against infection with potyviruses, and to understand how viruses circumvent or suppress host defense. The two major mechanisms of virus resistance in plants, gene-for-gene resistance and RNA silencing, are studied. Gene-for-gene resistance is unique to plants but has similarities to the mechanisms that protect mammalians against viruses. RNA silencing is a fundamental antiviral defense system in plants, animals and other multicellular organisms, and is involved in regulation of host gene expression. Studies on these mechanisms in plants will provide intrinsic, novel scientific information about virus defense induced upon infection. The program concentrates on resistance to potyviruses (family Potyviridae), the largest and the economically most important group of plant viruses, and to suppression of resistance by viruses. We use potato virus A (PVA) and potato virus Y (PVY) as model viruses.

Education of young scientists from developing countries in plant virology is one of our activities. Hence, capacity in solving problems caused by plant diseases can be enhanced. Most activities are situated in countries of East Africa and Central America.