Field Evaluation of Sugarcane Genotypes for Resistance to Leaf Scald Disease in China

Leaf scald is one of the major bacterial diseases causing severe losses to the sugarcane industry. Utilizing disease-resistant genotypes has proved to be the safest, most economical, and effective method to control it. Therefore, we evaluated leaf scald disease (LSD) on 166 sugarcane genotypes in a field trial over three years (2019–2021). We found that the disease incidence and severity varied among genotypes, and the percentage of diseased genotypes differed significantly across crop seasons. ANOVA analysis revealed that Genotype, Year, and Genotype-by-Year interaction significantly affected LSD occurrence. However, the broad-sense heritability (H_B²) for disease incidence (IC) and severity (DI) over three years was 0.72 and 0.68, respectively, suggesting that genetic factors play an essential role. To better classify the level of disease resistance, we performed cluster analysis using three years of disease incidence and severity; the accuracy of the cluster analysis was verified by discriminant analysis. Of the 166 sugarcane genotypes, 35 (21.08%) were highly resistant, 67 (40.36%) resistant, 24 (14.46%) moderately susceptible, 24 (14.46%) susceptible, and 16 (9.64%) highly susceptible. The total probability of discriminant analysis was 90.36%, indicating that the classification results were relatively accurate. The outcomes of this study provide a scientific basis for breeding and selecting resistant genotypes for commercial cultivation.