Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 3, 2010
Publication Date: N/A
Technical Abstract: Sunflower rust, caused by Puccinia helianthi Schewein, is a prevalent disease in many countries throughout the world. The USDA-ARS Sunflower Unit has released breeding materials identified as 'rust resistant' for several decades. However, constantly co-evolving rust populations have formed new virulent races for which many breeding lines have not been evaluated. The objectives of this study were to 1) evaluate selected sunflower lines for resistance to race 336, the predominant race in North America, and to race 777, the most virulent race; and 2) validate molecular markers known to be linked to rust resistance genes in the sunflower gene pool. A total of 106 entries, including 66 released USDA inbred lines, 14 germplasm lines, and 26 foreign germplasms developed specifically for rust resistance, were tested for their reaction to races 336 and 777. Most of the previously selected rust resistant lines were susceptible to races 336 and 777. Only 13 lines (12%) of the 106 entries tested were resistant to both races 336 and 777; whereas another six lines were resistant only to race 336. Most of the rust resistant lines had a hypersensitive reaction with flecks or type 1 pustules; only germplasm line TX16R had some plants with an immune reaction. The interspecific germplasm line, Rf ANN-1742, released as a fertility restorer in the 1990s, was resistant to both races and was identified as a new rust resistance source. A selection of 24 lines, including 19 lines resistant to races 777 or 336, four lines with other known rust resistance genes, and one susceptible check HA89, was screened with DNA markers linked to rust resistance genes R1, R2, R4u, and R5. The results indicated that the existing resistant lines have diverse genetic backgrounds. Durable genetic resistance using gene pyramiding will be effective for the control of rust.