Isozyme makers and their association with quantitative traits in relation to heterosis breeding in rice Oryza sativa L.

To determine association of some isozyme loci with some quantitative traits and to identify heterotic gene blocks which could be transferred to elite restorer lines, F1 progenies of the first backcross (BC1 F1) of the following crosses V20A/IR36R//IR36R, IR54752A/IR64R//IR64 and IR64R/Dular//Dular were studied and the isozymes were analyzed for each individual plant. Measurements of some quantitative traits like grain yield per plant and other yield related traits were taken on each individual plant and were grouped according to the allelic composition of each isozyme locus. The difference between the means of the quantitative traits of heterozygotes and homozygotes was determined using t-test. Grain yield per plant was found to be associated with Amp-3 and Est-2, both located on chromosome 3. Both isozyme loci and Pgi-2 which is also found in chromosome 3 were found to be associated with number of spikelets per panicle in the two crosses showing polymorphism in these loci. Est-2 was found to be associated in most of the quantitative traits studied namely: grain yield per plant, number of spikelets per panicle, number of secondary branches per panicle, number of primary branches per panicle, panicle length, and leaf length. Pgi-2 was found to be associated with two important yield components such as number of spikelets per panicle, and percent spikelet fertility and also with leaf width. Pgd-1 was found to be associated with percent spikelet fertility, Est-9 with leaf width and Amp-1 with tiller number and plant height. Est-9 and Amp-1 are located in chromosome 7 and chromosome 2, respectively, while the location of Pgd-1 is not yet known. The results suggest that isozyme loci could be used to mark some quantitative trait loci, however, to have more conclusive results, more crosses with diversed parents and larger population size should be used in the study