Multiple Allelism of the Locus Controlling Heading Time of Rice, Detected Using the Close Linkage with Blast-Resistance

Abstract

A genetic experiment was conducted to detect the multiple allelism of the locus controlling heading time in rice, with the aid of the close linkage with resistance to blast disease. Frve vaneties were used as parents "Fujisaka 5" was early-maturing, "Norin 8" "Toride 1" and "J 287" were medium and "J 315" was late FuJisaka 5 and Norin 8 are Japanese vaneties. The last three lines were developed from the cross between Norin 8 and an Indian variety "TKM.1" by the backcross breedmg program, and they had the Pi-z^t gene for blast resistance that was derived from TKM. 1 (NAGAI et al. 1970). Nine crosses were made between the parents, and the heading date of F₁ and F₂ plants was recorded in the field. The F₃ family of each F₂ plant was tested for resistance to the Ken 53-33 strain of blast fungus to estimate the F₂ genotype for the Pi-z^t gene, , In the six crosses segregating for resistance to Ken 53-33, the Pi-z^t gene was confirmed to control resistance of the hybrid populations (Table 1).