Executive Summary  
Although fungal plant pathogens are responsible for a large number of economically important diseases, few genes have been found that are suitable for engineering fungal resistance.  In previous work we identified a gene for mannitol dehydrogenase (MTD) that when over-expressed in transgenic Nicotiana greatly increases resistance to the mannitol-secreting fungal pathogen Alternaria alternata.   Although induction of the MTD gene appears to be a common defense response in plants, resulting levels of this enzyme are often insufficient to provide adequate protection against common fungal pathogens.  Fungal diseases such as leaf spots, powdery and downy mildews and Botrytis impact production and maintenance of many popular bedding plants.   Petunia (Petunia ´hybrida) and zonal geranium (Pelargonium ´hortorum) are of specific interest to our group, as both species are economically important and susceptible to significant fungal diseases. Our goal for this project is to over-express MTD in these two species, assess resulting changes in fungal disease symptoms and in the process produce cultivars that are resistant to a range of fungal pathogens.  By the end of the 3-year grant period, we plan to release germplasm to the industry for breeding fungal disease resistance in petunia.         This project would not only produce lower maintenance plants but also a proven process to create additional resistant varieties.  Growers would have reduced production expenses due to lower pest-management costs and decreased shrink caused by plant mortality and aesthetic damage due to fungal disease.  For the consumer, over-expression of this naturally occurring plant enzyme could result in healthier plants with lower maintenance requirements in the landscape, and thus lower environmental impact. 
            
For further information contact John Williamson at john_williamson@ncsu.edu