Submitted to: Sugar Cane International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/13/2005
Publication Date: 9/30/2005
Citation: Shine, J.M., Comstock, J.C., Dean, J.L. 2005. Comparison of five isolates of sugarcane rust and differential reaction on six sugarcane clones. Sugar Cane International 23:24-29. Interpretive Summary: A unique method was used to identify races of Puccinia melanocephala, the pathogen of sugarcane rust in Florida. The method was based on repeated inoculation of plants and obtaining data on estimates of percent infection, whole plant disease ratings, and plant height during the experiment that lasted for approximately five months. Fresh weight measurements were taken at the end of the experiment. Analysis of variance and single-degree-of freedom comparisons were used to identify races. Data demonstrated at least three and possibly rour races of P.melanocephala present in Florida.
Technical Abstract: The occurrence of pathological races of sugarcane rust (Puccina melancephala H. Sydow. and P. Sydoe.) in Florida was first reported in 1984. Cultivars that were resistant to the disease in the variety development program displayed susceptibility to the disease once expanded commercially. A study was conducted over two years to determine the effect on yield of six cultivars of sugarcane to five isolates of the sugarcane rust pathogen suspected to be differing pathological races. Sugarcane plants were grown in pots and inoculated under conditions favoring disease development while preventing infection of uninoculated control plants using the photoperiod treatment facilities at Canal Point. Plant height, estimates of percent infection and whole-plant disease ratings were recorded bi-weekly for 4 months during the late winter and spring of 1991 and 1992. Final plant height and fresh weight were measured at the end of the experiment each year. Areas under the disease progress curves (AUDPC) for plant height percent infection and disease rating were calculated. Analysis of variance and single-degree-of-freedom comparisons were used to interpret results for all response variables. These analyses indicated the existence of four pathogenic races of the rust pathogens in this experiment. These data coupled with field observations lead to the hypothesis that pathogenic rust variants develop within the sugarcane production region and parallel the development of new commercial sugarcane cultivars. The diversificaiton of commercial cultivars and identification of horizontal resistance mechanisms will reduce losses to sugarcane rust in the Florida sugarcane industry.