Maintenance of Genetic Purity within the Cms Lines of Rice Hybrids Using Molecular Markers

Full potential of any hybrid can be exploited by ensuring the supply of genetically pure seed to farmers. Genetic heterogeneity within CMS lines is the main source of impurity for hybrid seed production in rice. Cross pollination with pollen shedders other than cognate maintainer line and the maintainer line getting admixed with the seeds of CMS line are the main sources of contamination in CMS seed multiplication plots. Conventionally, CMS identification and seed purity assessment is done through grow out test (GOT), but nowadays molecular marker based approach isbeing widely adapted. The markers such as mtDNA, STMS, SSRs etc. assumes the greater significance for the purity assessment of CMS lines. Moreover, the molecular profiling of individual plants of CMS lines indicate the existence of plant-to-plant genetic variation although they are phenotypically similar. The residual heterozygosity or the heterogeneity detected at the molecular level may lead to the breakdown of CMS lines in longer run. Therefore, it is recommended that A and B line plants having similar marker profile should be used for paired mating to produce genetically homogenous seed of the A line.