Inheritance of Resrstance of Rice Vanetles to the Blast Fungus Strains Virulent to the Variety "Reiho"

Abstract

A gene analysis to identify the genes accounting for the moderate resistance of the rice variety Shin 2 and some other varieties to the blast fungus strain Kyu 77-07A was The differential varieties, Aichi Asahi (Pi-a) and carried out in the present study. Yashiro-mochi (Pi-ta), were found to be susceptible to the strain, while Ishikari Shirol*.e (Pi-i), Kanto 51 (Pi-k), Tsuyuake (Pi-k'!b), Fukunishiki (Pi-z) and Toride I (Pi-zt) were resistant, and Shin 2 (Pi-ks) and Pi N0.4 (Pi-ta2) moderately resistant. Therefore, Kyu 77-07A was classified as one of the strains belonging to race 102. Howver, the variety Reiho with the resistance gene Pi-ta2 was susceptible to this strain. Based on the knovn facts mentioned above, the objectives 0L the present study were' to determinA- whether Pi-ks is the gene responsible for the moderate resistance of Shin 2' to Kyu 77-07A along with the reason for the different reactions to Kyu 77-07A betweerL Pi N0.4 and Reiho which both have the same resistance gene Pi-ta2. For the gene analysis, the F₂ or F₃ plants of the crosses were inoculated with Kyu 77-07A and three other fungus strains using the spraying rnethod when the plants were at the four- to five-1eaf stage. Two varieties, Mineyutaka. and Saikai 155 belonging to the Shin 2 type varieties, were used as the representative parents of the varieties susceptible to Kyu 77-07A for the crosses.