Submitted to: American Society of Sugar Cane Technologists
Publication Type: Abstract only
Publication Acceptance Date: 6/2/2010
Publication Date: 6/18/2010
Citation: Hale, A.L., Dufrene Jr, E.O., Grisham, M.P. 2010. Evaluation of brown rust resistance in the Louisiana basic breeding program’s first clonal trial. Journal of the American Society of Sugar Cane Technologists. 30:152. Interpretive Summary:
Technical Abstract: Over the past decade, the Louisiana sugarcane industry has experienced increasing levels of pressure from brown rust (Puccinia melanocephala). In 2000, an epidemic spread throughout the Louisiana industry, severely affecting the state’s top yielding variety, previously resistant LCP85-384, which at the time comprised roughly 71% of the state’s sugarcane acreage. The variety was replaced by other resistant varieties, such as Ho95-988, HoCP96-540, and L99-226. Unfortunately, most of the new varieties also became susceptible to brown rust within a few years after release. In the spring of 2009, a severe rust epidemic developed on the USDA, ARS, Sugarcane Research Laboratory’s (SRL) research farm in Schriever, Louisiana. In an attempt to identify new, and more durable sources of brown rust resistance among our breeding population, 2125 wide crosses and early-generation backcrosses were rated for resistance to the disease. These clones were part of the first clonal stage of the SRL’s basic breeding program and were diverse in ancestory. Clones were derived from 57 male parents, 81 female parents, and 144 cross combinations. Clones were rated for resistance on a scale of zero to nine (0=no rust visible; 9=completely brown leaves); the average rust score was 3.0. Commercial standards included in the trial were HoCP96-540, L01-283, HoCP00-950, and L99-226, and they had average rust ratings of 3.7, 1.8, 3.0, and 4.5, respectively. Ten percent of the basic breeding clones evaluated were rated a 1.0 for rust (very minor flecking), followed by 28.0, 26.5, 21.5, 8.2, 4.4, 1.0, 0.3 and 0 percent for ratings of 2 – 9, respectively. Significant differences (a=.05) were observed between different cross combinations. When advancements were made to the second clonal stage, rust ratings were taken into account. The average rust rating was shifted slightly toward resistance to brown rust in the next stage of selection, and individuals with rust ratings greater than 4 were dropped from further testing with few exceptions (if they contained another trait of interest). Percentage of individuals advanced to the second clonal stage of the program included 13.0, 35.8, 29.6, 14.7, 4.9, 1.6, 0, .3.0, and 0 for ratings of 1-9 respectively. Results from this study will help in the selection of parental material for breeding future rust-resistant varieties.