A Method for Inoculation and Evaluation of Rice Sheath Blight Disease

Area of Science:

• Plant Pathology
• Agronomy
• Genetics

Background:

• Sheath blight, caused by Rhizoctonia solani, is a major global rice disease.
• No rice cultivars exhibit complete resistance, necessitating improved evaluation methods.

Purpose of the Study:

• Develop effective and uniform infection methods for rice sheath blight.
• Establish accurate evaluation techniques for disease resistance analysis.

Main Methods:

• Tested three inoculum types (agar block, liquid cultured mycelia ball, mycelia suspension) on resistant and susceptible rice cultivars.
• Utilized aluminum foil to maintain humidity, achieving 100% infection rates.
• Compared two disease severity evaluation methods and developed a new susceptibility index formula.

Main Results:

• Liquid cultured mycelia balls resulted in significantly longer lesions (5.4 cm) compared to agar blocks (2.4 cm) and mycelia suspension (1.6 cm).
• The new susceptibility index formula provided the most accurate disease evaluation across diverse rice cultivars.
• Late heading date cultivars generally showed higher sheath blight resistance.

Conclusions:

• The developed methods enhance the study of rice sheath blight resistance at multiple biological levels.
• The new susceptibility index is a reliable tool for accurate sheath blight assessment in rice breeding programs.
• Heading date is a potential factor influencing sheath blight resistance in rice.