Comparison of Three Experimental Designs for the Field Assessment of Resistance to Rice Blast Disease (Pyricularia oryzae)

The reliability and the effectiveness of three field experimental designs for the assessment of varietal resistance to Pyricularia oryzae was studied for 2 years. Plants were arranged in the field using two sets of three designs: randomized compete block (RCB), adjacent control (AC) and honeycomb (HC). In the first set, plants were inoculated with the fungus and in the second one, plants were naturally infected. Four varieties were used, Maratelli (susceptible control), Roxani, Selenio and Senia (main varieties). Disease progress was recorded as leaf and neck blast. The number of plants of the main varieties required in each design was higher for RCB (90) and lower for AC and HC (30 and 32, respectively). Results showed that disease severity was significantly different in the varieties studied and it was consistent and not affected by the plant arrangement in the field. All experimental designs were reliable and effective for the assessment of leaf and neck blast under inoculation or natural infection. AC and HC designs had the advantage of requiring fewer plants over RCB one. This could be important in cases where seed availability is a limiting factor.