Submitted to: American Society of Sugar Cane Technologists
Publication Type: Abstract Only
Publication Acceptance Date: June 20, 2004
Publication Date: June 25, 2004
Citation: Comstock, J.C., Miller, J.D. 2004. Ratoon stunt effects on yields of sugarcane. American Society Of Sugar Cane Technologists. 24:106. Interpretive Summary: Ratoon stunt is a major disease of sugarcane worldwide and in yield trials in South Florida the cane weight and sugar per plot were reduced. Although not all the results of individual sugarcane cultivars were significant, almost all comparisons of diseases versus healthy plots the infected plots were reduced. The results indicate ratoon stunt is still important and the commercial cultivars grown in Florida can have reduced yields if infected by the ratoon stunt pathogen, Leifsonia xyli subsp. xyli.
Technical Abstract: The effect of Leifsonia xyli subsp. xyli, ( Lxx) the causal agent of ratoon stunt on yield was evaluated in three yield trials using eight CP-cultivars by harvesting the plant and first-ratoon crops. Plots were established by cutting a single 2-m disease free seedcane stalk in half at planting. In the first test, the treatments were healthy ( non-inoculated) and Lxx inoculated, by dipping the freshly cut ends in a container of expressed juice obtained from Lxx infected stalks of CP 53-1, a cultivar known to harbor high populations of the pathogen. In the second trial, stalks were cut from plots of the first test confirmed healthy and Lxx-infected by a tissue blot immunoassay. The Lxx infected stalks were also inoculated at planting. In the third trial, stalks were only cut from the healthy plots of the first trial and inoculated by cutting with knives dipped in juice expressed from infected CP 53-1. Yield parameters were determined by stalk counts per plot and the fresh weight and sucrose analysis of a 5 stalk sample of each plot. The disease state of each stalk sampled for sucrose analysis was determined by tissue blot immunoassay using a 10 to 15 cm section cut from the base of each stalk and analysis of data was conducted on plots of confirmed disease status. Combining the data from all cultivars, the yield parameters were reduced by 3.5% to 15.8% in Lxx infected plants compared to healthy plants. In individual cultivars yield losses were not always statistically significant. In the first trial, disease-free plots in 4 of 8 cultivars in the plant and 6 of 8 cultivars in the first ratoon had higher yields of sugar per plot. In this trial, the inoculations were not fully successful and there were fewer Lxx infected plots of some cultivars. In the second trial, the yield of sugar per plot for disease-free plots was higher in all 8 cultivars in the plant and 7 of 8 cultivars in the first ratoon crop. In the third trial the yield of sugar per plot in disease-free plots was higher for 6 of 8 cultivars in the plant and for all cultivars in the first ratoon. Based on the overall results, Lxx infection causes yield losses of most CP sugarcane cultivars.