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ARS Home » Plains Area » Fargo, North Dakota » Edward T. Schafer Agricultural Research Center » Sunflower and Plant Biology Research » Research » Publications at this Location » Publication #191038
Title: DIVERSITY IN THE SUNFLOWER: PUCCINIA HELIANTHI PATHOSYSTEM IN AUSTRALIA

Author
item SENDALL, B - THE UNIV QLD, AUSTRALIA (
item KONG, GARY - DEPT PRIM IND & FISH, AS
item GOULTER, K - THE UNIV QLD, AUSTRALIA (
item AITKEN, E - THE UNIV QLD, AUSTRALIA (
item THOMPSON, S - DEPT PRIM IND & FISH, AS
item MITCHELL, J - DEPT PRIM IND & FISH, AS
item KOCHMAN, J - DEPT PRIM IND & FISH, AS
item LAWSON, W - DEPT PRIM IND & FISH, AS
item SHATTE, T - DEPT PRIM IND & FISH, AS
item Gulya Jr, Thomas

Submitted to: Australasian Plant Pathlogy Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2006
Publication Date: 11/2/2006
Citation: Sendall, B.C., Kong, G.A., Goulter, K.C., Aitken, E.A., Thompson, S.M., Mitchell, J.H., Kochman, J.K., Lawson, W., Shatte, T., Gulya Jr, T.J. 2006. Diversity in the sunflower: Puccinia helianthi pathosystem in Australia. Australasian Plant Pathlogy. 35(6):657-670.

Interpretive Summary: Sunflower rust is a pathogen of worldwide distribution, but it is most frequently encountered on sunflower in the United States and Australia. There is a wide diversity of "physiological races" of sunflower rust in both countries, and plant breeders must select for individual genes to give resistance to each and every rust race. It is important not only to know which races occur in a given area, but also to understand how new races develop. Ms. Sendall spent a few weeks in my lab isolating DNA from our collection of North American rust races, and used this to continue her research back in Australia. By using molecular methods to compare rust races from North America and Australia, she was able to determine that rust in Australia is much more diverse genetically. The team's development of molecular markers has also helped to identify new resistance genes in cultivated sunflower and these should also be useful in our search for rust resistance genes in wild Helianthus species.

Technical Abstract: Sunflower rust caused by Puccinia helianthi is the most important disease of sunflower in Australia with the potential to cause significant yield losses in susceptible hybrids. Rapid and frequent virulence changes in the rust fungus population limit the effective lifespan of commercial cultivars and impose constant pressure on breeding programs to identify and deploy new sources of resistance. The purpose of this work was to determine how new pathotypes of P. helianthi are generated. Wild sunflower populations provide a continuum of genetically heterogeneous hosts on which P. helianthi can potentially complete its sexual cycle. Virulence surveys revealed that diverse pathotypes of P. helianthi are found in wild sunflower populations, most likely because sexual recombination and subsequent selection of recombinant pathotypes occurs there. Molecular analysis of a worldwide collection of P. helianthi indicated that Australian isolates of the pathogen are more diverse than overseas isolates. Additionally, the presence of the same pathotype in different genotypic backgrounds supported the contention that sexual recombination has occurred at some time in the Australian population of P. helianthi. Molecular markers were identified for a large number of previously uncharacterised sunflower rust resistance genes. These markers have been used to detect resistance genes in breeding lines and wild sunflower germplasm. A number of virulence dissociations were identified in P. helianthi, to which the corresponding resistance gene combinations are currently being introgressed with breeding lines to generate hybrids with durable resistance to sunflower rust.