Molecular diversity in castor (Ricinus communis L.)

•Dominant markers targeting different regions of the genome were employed for assessment of genetic variation in castor accessions from different geographical regions.•Random amplified polymorphic markers exhibited relatively higher level of polymorphism as compared to inter simple sequence repeat and start codon targeted markers.•Study resulted in 30 accession specific markers that can be used as signature profiles for 16 of the 31 accessions studied.•Showed divergence among the Indian elite parental lines and exotic germplasm.

Castor (Ricinus communis L.), a non-edible oilseed crop of the tropics assumes commercial importance due to its great utilization value in industry, medicine and agriculture. The present investigation has been undertaken to assess the extent of genetic diversity in 31 accessions of castor representing seven geographic areas in the world using RAPD (random amplified polymorphic DNA), ISSR (inter simple sequence repeat) and SCoT (start codon targeted polymorphism) primers. Among the three marker systems, RAPD had revealed highest average percentage of polymorphism (54) while SCoT markers disclosed the lowest average percentage of polymorphism (21). The average PIC (polymorphic information content) values ranged from 0.20 (ISSR) to 0.24 (RAPD and SCoT). The average marker index for both RAPD and SCoT markers was same (0.07) and it was comparatively low for ISSR markers (0.05). The average resolving power was maximum for ISSR (4.79) compared to that of RAPD and SCoT primers. Out of 157 polymorphic markers, 30 markers resulted in accession specific bands. The accession, RG-1171 had more number of accession specific bands with all the three marker systems, and the RAPD primer OPL-9 produced maximum number of accession specific bands. Combined data of the 3 marker systems classified the accessions into three major clusters, cluster I included 4 accessions each from USA and India; cluster II was large and included 10 accessions from Nigeria, 3 accessions from USA, 2 accessions each from Kenya, India and Egypt, 1 accession each from Brazil and USSR; cluster III included two accessions from India. Use of three dominant marker systems targeting different regions of the genome (random, repeat regions and functional regions of the gene) on castor germplasm from seven geographical regions indicated hither to modest level of genetic variability but led to identification of accessions with several unique bands which could be further investigated for exploitation in the breeding programmes.