Genes Piz-t Research Articles

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

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 was early-maturing, Toride 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-zt 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-zt gene, , In the six crosses segregating for resistance to Ken 53-33, the Pi-zt gene was confirmed to control resistance of the hybrid populations (Table 1).

Tight Linkage of Blast-Resistance with Late Maturity Observed in Different Indica Varieties of Rice

A tight linkage between blast-resistance and late maturity with a recombination value of 3.5±0.5% was observed in the progenies of several different japonica ×indica crosses in rice. The blast-resistance in the sixcrosses was controlled by the identical gene Pi-zt and the lateness in maturity was due to a photoperiod-sensitive gene. These two genes were linked with the genes for apiculus color and for digestibility of milled rice in dilute alkali, and were located in the linkage group I in rice. The significance of the tight linkage in practical rice breeding was discussed.