Abstract
The nature and magnitude of heterosis was studied in 10 Mutant x Mutant (MM) hybrids and 5 Mutant x Parent (MP) hybrids of aromatic rice. The frequency of positive heterosis in hybrids was more in MM hybrids than MP hybrids for panicle length, panicle weight, number of secondary branches per panicle, spikelet number per panicle, biomass yield, harvest index, and grain yield per plant. The MM hybrids exhibited higher levels of heterosis than MP hybrids for most of the characters indicating greater genetic diversity among mutants themselves than between mutant and parent. Heterosis in grain yield in the hybrids was primarily associated with heterosis in harvest index and (or) biomass yield. The possibility of pleiotropic effects of mutant gene(s) in the expression of mutant heterosis could not be ruled out.
