An Exploratory Study on Allelic Diversity for Five Genetic Loci Associated with Floral Organ Development in Rice

Abstract

Allelic diversity for five genetic loci ( DL, FON4, OsMADS24, OsMADS45 and Spw 1) associated with floral organ development were investigated among a small heterogeneous rice population which included one wild species ( O. rufipogon Griffiths), one indigenous less popular natural floral organ mutant ( O. sativa var. indica cv. Jugal), one indigenous normal line ( O. sativa var. indica cv. Bhutmoori) and one improved high yielding line ( O. sativa var. indica cv. IR 36). Detailed spikelet morphology showed that var. Jugal had variable number (1 - 3) of carpels within a single spikelet which was unique and resulted in variable (1 - 3) number of kernels within a single matured spikelet (grain). The genomic DNA of each investigated line was amplified with primer sequences designed from the selected genetic loci and the derived polymorphism profiles were used for study of allelic diversity for the studied loci. The derived genetic distances among the rice lines were used for dendrogram construction. In constructed dendrogram, the mutant genotype (Jugal) showed highest similarity with the wild rice ( O. rufipogon ) instead of the rice lines. To verify this finding, the genomic DNA of each studied line was also amplified with four SSR loci, tightly linked to saltol QTL, mapped to rice chromosome 1. The amplified products were screened for polymorphism and another dendrogram was constructed to reveal the genetic distance among the lines for selected salt tolerance linked SSR loci. In SSR derived dendrogram, the wild rice ( O. rufipogon ) got totally separated from the all three rice genotypes though all the studied four lines showed equal sensitivity for salt sensitivity in a physiological screening experiment. From the combined experiment, it can be concluded that genetic architecture of floral organ development loci in var. Jugal may have some uniqueness which is not present in normal rice but common to O. rufipogon , a species which is regarded as immediate progenitor of present day modern rice ( O. sativa ). Though this uniqueness was not confirmed by second set genetic loci associated with salt tolerance in rice, the information resulted from this experiment was preliminary and based only on allelic size (molecular weight of amplicon), which should be confirmed through sequence analysis for further analysis.