Plant Genome IV Conference Plant Genome IV Conference
Comprehensive molecular map of rice has been developed and rice is becoming a pivotal system for cereals for molecular biology reseach because of its small genome size and syntany with other cereal genomes. However, no information was available about arm location of RFLP markers and position of centromeres on the molecular map. We developed a set of secondary and telotrisomics and used these for assigning RFLP markers to specific chromosome arms and mapping position of centromeres. The secondary and telotrisomics (developed in IR36 background) representing all the 12 chromosomes of rice were crossed with another tropical japonica line MaHae. The F1 primary trisomic, F1 secondary/telotrisomic, F1 disomic sib and parental lines IR36 an MaHae formed a set of plant material for each of the 12 chromosomes. RFLP analysis was carried using standard protocols. An F1 secondary trisomic has three copies of IR36 (for the arm for which it is secondary) and one of MaHae and accordingly intensity of IR36 band specific for a given marker present on that arm is three times that of MaHae. In contrast if the marker in question is not located on the arm for which it is secondary trisomic then the F1 secondary trisomic has similar intensities of bands corresponding to IR36 and MaHae alleles. Telotrisomics have behave the same way as secondary trisomics except that intensity of IR36 is twice the intensity of MaHae band. Based on this rationale about 170 RFLP markers covering all the 12 chromosomes were assigned to specific chromosome arms and positions of the centromere were mapped on all the 12 linkage groups of rice molecular map and hence corrected orientation of the map is presented.