Vertical distribution of leaf blast lesions in mixtures of rice cultivar Sasanishiki and its resistant near-isogenic line

The vertical distribution of leaf blast lesions caused by the fungus Pyricularia grisea was studied to estimate the degree of leaf blast suppression in rice multilines in experimental paddy fields for 4 years. Leaf blast in 1 : 1 and 1 : 3 mixtures of susceptible rice cultivar Sasanishiki and its resistant near-isogenic line, Sasanishiki BL7, developed slower than that in pure stands of Sasanishiki. The average distance of lesions on leaves from the ground in the 1 : 3 mixtures was significantly lower than that in the pure stands at the end of leaf blast epidemics (at booting stage). This result shows that the distribution of leaf blast lesions in the upper layer differs between the susceptible pure stands and the 1 : 3 mixtures at the end of leaf blast epidemics.