Infectivity Titration for Assessing Resistance to Leaf Scald Among Sugarcane Cultivars

Area of Science:

• Plant Pathology
• Agricultural Science
• Bacteriology

Background:

• Leaf scald disease, caused by Xanthomonas albilineans, poses a significant threat to sugarcane production.
• Accurate assessment of sugarcane cultivar resistance is crucial for disease management strategies.

Purpose of the Study:

• To evaluate the potential of infectivity titration for assessing sugarcane resistance to leaf scald disease under greenhouse conditions.
• To compare the efficacy of infectivity titration with traditional field observations.

Main Methods:

• Greenhouse experiments using single-bud sugarcane cuttings inoculated with varying concentrations (10^1, 10^5, 10^8 CFU/ml) of Xanthomonas albilineans.
• Monitoring disease symptoms and latent infections over 210 days post-inoculation.
• Estimating the ED50 (effective dose for 50% infection) using probit analysis.

Main Results:

• Infectivity titration yielded ED50 values ranging from 3.0 to 12.3 and 3.1 to 9.8 across two experiments.
• ED50 values showed good agreement between experiments and correlated well with field observations of natural disease incidence.
• Cultivar responses based on ED50 aligned with symptom development, death, and recovery rates.

Conclusions:

• Greenhouse infectivity titration is a viable alternative to field testing for evaluating sugarcane resistance to leaf scald.
• This method offers a reproducible and efficient way to assess cultivar resistance to Xanthomonas albilineans.
• Infectivity titration can be used with a single inoculum concentration for practical resistance assessment.