Effects of Major Genes Controlling Morphology of Panicle in Rice

Abstract

The effects of Ur-1 (Undulate rachis), Dn-1 (Dense panicle), Iax (lax panicle), sp (short panicle), Cl (Clustered spikelets) and ri (verticillate rachis) were investigated. Ur-1, Dn-1 and Cl are incompletely dominant genes, while lax, sp and ri are recessive genes. F₂ populations between one cultivar, Ishikari and 6 Iines carrying the respective 6 major genes, and the isogenic lines of Ur-1 and Dn-1 of another cultivar, Shiokari were used. It is inferred that Ur-1 increases the number of spikelets per panicle due to the increases of the number of secondary branches per primary branch and the number of spikelets per secondary branch, but decreases the number of panicles per plant, 100 kernel weight and spikelet fertility. In the F₂ of Ishikari×N-55 containing Ur-1, the Ur-1/Ur-1 and Ur-1/+genotypes were higher than the +/+ genotype in the perventage of panicle weight, but the difference among the three genotypes in panicle weight per plant was not significant. Dn-1 increases the number of secondary branches per primary branch and the number of spikelets per panicle, but decreases lengths of panicle, primary branch and secondary branch. Lax decreases the number of spikelets per primary branch and the number of spikelets per secondary branch, resulting in decrease of the number of spikelets per panicle. sp decreases all of the four components of the number of spikelets per panicle, viz. the number of primary branches per panicle, the number of secondary branches per primary branch, the number of spikelets per primary branch and the number of spikelets per secondary branch. Cl reduces length of secondary branch. ri acts to form the characteristic panicle that two to 10 primary branches grow verticillately from a few points on the panicle axis.