ARS | Publication request: Utilization of a major brown rust resistance gene in sugarcane breeding

Submitted to: Molecular Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 12, 2012
Publication Date: October 1, 2012
Citation: Glynn, N.C., Laborde, C., Davidson, R., Irey, M., Glaz, B.S., Comstock, J.C., D'Hont, A. 2012. Major Brown Rust Resistance Gene (Bru1) Utilization in Sugarcane Breeding and Disease Management. Molecular Breeding. 30:3. DOI: 10.1007/s11032-012-9792-x

Interpretive Summary: Molecular detection techniques have been incorporated into the Canal Point Breeding and Selection Programs to determine the presence of the major brown rust resistance gene, Bru1, in both parental clones and clones being developed. Detection of the Bru1 brown rust resistance gene will greatly enhance the development of resistant commercial cultivars for the Florida Sugarcane Industry. Although Bru1 is the major resistance gene there are there are other sources of resistance and using this molecular technique in combination with pathogen inoculation will determine if it is Bru1 determining brown rust resistance or an alternative sources of resistance.

Technical Abstract: Brown rust, caused by Puccinia melanocephala has had devastating effects on sugarcane (Saccharum spp.) breeding programs and on commercial production. The discovery of Bru1, a major gene conferring resistance to brown rust represented a substantial breakthrough and markers for the detection of Bru1 are the first available for molecular breeding in sugarcane. The contribution of Bru1 towards brown rust resistance in the Canal Point (CP) sugarcane breeding program was determined as a means of directing future strategies for brown rust resistance breeding in sugarcane. Bru1 was detected in various sugarcane genotypes from the CP program. Bru1 was detected in 285 of 1072 (27%) clones used for crossing in the CP program; this germplasm represents the genetic base for sugarcane cultivar development in Florida. Among cohorts, the frequency of Bru1 was greatest in CP clones (42%) and lowest among Louisiana clones (6%). Bru1 was not detected in any of 18 clones with year assignments earlier than 1953. The frequency of Bru1 increased from 15% among clones with year assignments 1975-1985 to 47% among clones in the current decade. The increase coincided with the introduction of brown rust to Florida. Bru1 was detected in 155 (32%) of 485 parental clones tested for brown rust susceptibility at two field locations. Of clones classed as resistant to brown rust, 154 (59%) contained Bru1 yet none of 100 clones classified as susceptible contained the gene. Bru1 was detected in 667 (44%) clones in the second clonal stage of selection, 87% of which were free of brown rust symptoms. Bru1 is the predominant source of resistance in the Florida sugarcane genetic base. Efforts to identify and integrate new brown rust resistance genes must be pursued in order to minimize the risks associated with a future breakdown in major gene resistance provided by Bru1.