Research Interests

My research has ranged over several areas of plant virology. Early work centered on the discovery, properties, relationships, seed and vector transmission, and ecology and control of soil-borne viruses that I found to have nematode or fungal vectors. Later, with two groups of nematode-transmitted viruses, tobraviruses and nepoviruses, I studied the different kinds of interplay between, and genetic roles of, the two genomic RNA molecules. With tobraviruses, I detected unequal variation of the two genome parts and RNA recombination in nature. I also helped to develop a modern plant virus taxonomy. More recently, I contributed to discovery of the mechanism of potyvirus transmission by aphids, transgenic virus resistance conferred by viral satellite nucleic acid, and viral gene silencing associated with recovery from nepovirus infection. Two decades ago, I reported the circularity of the single-stranded genomic DNA of whitefly-transmitted geminiviruses. I have since detected and differentiated many of these viruses (which are prevalent in the tropics and subtropics) and discovered their geography-related antigenic variation. My latest studies, on severe geminivirus epidemics in cassava and cotton, have revealed the occurrence of interspecific recombination and its probable importance in evolution of these viruses.

Membership Type

International Member

Election Year


Primary Section

Section 62: Plant, Soil, and Microbial Sciences

Secondary Section

Section 44: Microbial Biology