Effect of Mixing Ratio of Blast-Resistant Isogenic Lines on Rice Yield of the Multiline

Abstract

Yielding ability of multiline composed of the blast resistant isogenic lines (Pia, Pii, Pita-2 and Piz) and original line (+) was evaluated in a paddy field with severe blast epidemic (a pathogenic race 137). When 25 % of the original line was replaced by each isogenic line, the grain yield and percentage of yield decrease were greatly affected by the presence of Pita-2 and Piz. The yield was greatly influenced by the mixing ratio of the resistant lines. The multiline composed of the four true resistant isogenic lines was the best to maintain a high yielding ability, and had a grain yield of 411.7 g m^-2 with a 10.6 % yield decrease compared with the resistant line alone. On the other hand, the grain yield of the original line was 259.1 g m^-2 with a 43.7 % yield decrease. Thus, the advantage of the multiline was estimated to be a 152.6 g m^-2 yield increase and 33.1 % improvement of yield decrease.