College of Agriculture and Life Sciences
Department of Plant Pathology

1998 Nusbaum Scholar

Sonia Herrero

l to r: Dr. R. Rufty, Dr. Sonia Herrero, Dr. O. W. Barnett, Dr. M. Daub

Sonia Herrero, a native of Segovia, Spain, received her B.A. degree in Biology from the College of St. Catherine in St. Paul, MN in 1990. She completed her M.S. degree with Becky Rufty in Crop Science at NC State University with research on cyst nematode resistance in tobacco. She was awarded both an Outstanding Masters Student Award and the prestigious E. G. Moss Fellowship for continuation of her studies in a Ph.D. program. She began her studies leading to the Ph.D. degree, under the mentorship of Margo Daub in Plant Pathology and Rebeca Rufty in Crop Science, in May of 1994. In 1997, she was awarded the Dow AgroSciences Award for Outstanding Research in the Department of Plant Pathology at NC State University. Sonia is currently a Postdoctoral Associate at the National Center for Biotechnology in Madrid, Spain, where she is working on tomato bushy stunt virus, specifically on studying the satellite RNA of this virus and development of transgenic resistance.

Sonia's Ph.D. research focused on investigating the factors that influence whether transgenic plants can be a viable option for disease control by growers. She chose as her model for this work, tobacco transformed for resistance to tomato spotted wilt virus. TSWV is a problem both on field crops such as tobacco and peanut, as well as on many greenhouse ornamentals. The utility of coat-protein-mediated transgenic resistance to plant viruses has been championed for some time, but to date there are few studies that address issues that will influence the successful deployment of this technology for practical crop improvement. Sonia's thesis focused on several factors, including cultivar effects on expression of resistance; stability of resistance in advanced generations; heritability of resistance in crosses (i.e. ability to use transgenics as a source of resistance in a breeding program); and the ability of strains of the virus to overcome resistance both in the greenhouse and in the field.

Sonia's research is some of the first to demonstrate that there is a definite cultivar effect on the expression of virus coat-protein mediated resistance and that this expression holds when the lines are tested under field conditions. Her results support epidemiological studies that suggest that TSWV does not spread from plant to plant in tobacco fields, but that disease is a result of an initial flush of infection.

In addition to her work on the practical implications of transgenic resistance to TSWV, Sonia also conducted studies to determine the molecular events that correlate with resistance. Unlike conventional dominant genes, which generally express in all plants into which they are transferred, only a small percentage (ca. 10% in our work) of plants transformed with virus coat protein genes actually show resistance to virus infection., even if they are expressed. The reason(s) some plants are resistant and others are not has never been answered. Her results showed that resistance could be attributed to different events in different lines. In one family she studied, resistance was correlated with gene dosage. In another family, the presence of a single highly transcribed insertion was adequate to impart resistance.

For the excellence in her research at the Ph.D. level, the Department of Plant Pathology is pleased to present Sonia Herrero with the Nusbaum Scholar Award for 1998.

– Lee Campbell