Poster: Plant-pathogen interactions

Abs # 557: Differential expression of genes in loblolly pine challenged with the fusiform rust fungus, Cronartium quercuum f.sp. fusiforme.

Presenter:	Myburg, Henrietta , cassi_myburg@ncsu.edu
Authors	Myburg, Henrietta  (A)   Van Zyl, Len  (A)   Amerson, Henry  (A)   Nelson, Dana  (B)   Kubisiak, Tom  (B)
Affiliations:	(A): Forest Biotechnology Group, Dept. of Forestry, NC State University. (B): USDA Forest Service, Southern Inst. of Forest Genetics, Saucier, MS.

Cronartium quercuum f.sp. fusiforme (Cqf.) is the causal agent of fusiform rust disease of southern pine species, such as loblolly pine (Pinus taeda). Genomic mapping studies in loblolly pine have identified several major pathotype-specific genes that confer resistance to fusiform rust disease. One of these resistance genes, Fr1, is utilized in this study. Although specific resistance genes have been recognized, the underlying molecular processes involved in pathogen infection, disease response and gall formation are not clear and needs explanation. Research is currently underway that will enhance our understanding of these processes. This includes microarray analyses of differentially expressed genes in segregants of a loblolly pine clone that is heterozygous (R1r1) at the Fr1 locus. This clone was crossed with a homozygous recessive individual (r1r1). The segregants inherited either the resistance (R1) or the non-resistance allele (r1) from the heterozygous parent. The progeny from this cross were challenged with a single-spore Cqf. isolate that is homozygous avirulent at the corresponding Avr1 locus. With this inoculation the R1 progeny would display an incompatible (no disease) response while r1 progeny would become diseased (compatible response). Harvesting of control and inoculated seedlings was done over a period of 4 months. We are therefore able to study differential gene expression in compatible and incompatible interactions over time. Results and progress to date from this study will be presented.