Abstract:
Fifty-four Medicago laciniata (L.) Miller accessions from diverse locations in eastern Australia, Africa and Israel were characterized for genotypic differences by restriction endonuclease cleavage of genomic DNA and probing with radio-labelled DNA sequences to detect restriction fragment length polymorphisms (RFLP). Digestion of the genomic DNA with the restriction endonuclease, Bam HI, and probing with the complete ribosomal DNA (rDNA) repeat unit of soybean (pGmrl) and its subclones revealed that the variable region in M. laciniata spans the Bam H1 sites of the intergenic spacer region between the 18s and 26s DNA. The length variation in the rDNA repeat unit clearly distinguished South African from Australian accessions. The rDNA variants from SA1847 (Morocco) and SA7750 (Tunisia) were the same as the Australian accessions and slightly larger than the rDNA spacer variant unique to SA3428 (Israel). When Eco R1 digested M. laciniata genomic DNA was probed with peroxidase and extensin cDNA clones, all Australian accessions were again characterized by the same RFLP genotype with further differentiation between African and Israeli accessions. An accession of unknown origin, SA3412, possessed the same RFLP genotype as the Australian accessions for all endonuclease and probe combinations. For the African accessions, differences in RFLP genotype were more frequent than differences in phenotype (leaflet laciniation and colour). However, of three South African accessions with the same RFLP genotype, SA26844, SA26847, and SA26848, SA26847 had more pronounced leaflet laciniation.