IDENTIFICATION OF MINOR DNA VARIATIONS IN RICE SOMACLONAL VARIANTS

Some somaclonal variants derived from a landrace rice variety, Indraya ni, were shown to be high yielding and resistant to multiple diseases in previous analysis carried out in our laboratory. An attempt was mad e to assess the effect of culturing and regeneration of rice plants on DNA variation at microsatellite loci in R-2 progeny of callus-derived rice plants. Different somaclones of the rice line Indrayani differin g in yield and disease response thigh, low and no change in yield, as compared to the original genotype) were used as genetic material for t hese analyses. Analysis of microsatellite loci was accomplished by dig esting DNA from regenerated rice somaclones and assaying for polymorph isms at microsatellite loci by in-gel hybridization with synthetic oli gonucleotide probes such as (GATA)(4), (CAC)(5) and (TG)(10). Specific variation at a PCR-amplified locus containing three internal microsat ellite repeats (1E(6) using restriction site fingerprinting was also i nvestigated. The locus-specific amplification of a sequence-tagged mic rosatellite marker followed by digestion with HinfI and Sau3AI restric tion endonucleases showed differences in some somaclonal variants. The technique used in this study enables monitoring of DNA changes in suc cessive generations of somaclonal variants as a measure of DNA variabi lity and possibly to identify the regions which are responsible for sp ecific traits.