RIBOSOMAL DNA, PEROXIDASE AND EXTENSIN VARIATION IN GENOMIC DNA OF MEDICAGO-LACINIATA (L) MILLER FROM AUSTRALIA AND AFRICA

Fifty-four Medicago laciniata (L.) Miller accessions from diverse loca tions in eastern Australia, Africa and Israel were characterized for g enotypic differences by restriction endonuclease cleavage of genomic D NA and probing with radio-labelled DNA sequences to detect restriction fragment length polymorphisms (RFLP). Digestion of the genomic DNA wi th the restriction endonuclease, Bam H1, and probing with the complete ribosomal DNA (rDNA) repeat unit of soybean (pGmr1) and its subclones revealed that the variable region in M. laciniata spans the Bam H1 si tes of the intergenic spacer region between the 18S and 26S DNA. The l ength variation in the rDNA repeat unit clearly distinguished South Af rican from Australian accessions. The rDNA variants from SA1847 (Moroc co) and SA7750 (Tunisia) were the same as the Australian accessions an d slightly larger than the rDNA spacer variant unique to SA3428 (Israe l). When Eco R1 digested M. laciniata genomic DNA was probed with pero xidase and extensin cDNA clones, all Australian accessions were again characterized by the same RFLP genotype with further differentiation b etween 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 accessio ns, differences in RFLP genotype were more frequent than differences i n 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.