Table 1.

Disease rating scale (IRRI, 2013).

Category	Symptoms
0	No lesion
1	Small brown specks of pinhead size without sporulating center
2	Small roundish to slightly elongated, necrotic grey spots, about 1–2 mm in diameter with a distinct brown margin and lesions are mostly found on the lower leaves
3	Lesion type is the same as in scale 2, but significant number of lesions are on the upper leaves
4	Typical sporulating blast lesions, 3 mm of longer, infecting less than 2% of the leaf area
5	Typical blast lesions infecting 2–10% of the leaf area
6	Blast lesions infecting 11–25% leaf area
7	Blast lesions infecting 26–50% leaf area
8	Blast lesions infecting 51–75% leaf area
9	More than 75% of leaf area affected