RAPD ANALYSIS REVEALS A LOW-RATE OF OUTCROSSING IN BURR MEDIC (MEDICAGO-POLYMORPHA L.)

Although burr medic (Medicago polymorpha L.) is commonly considered a self-pollinating species, intrapopulational variation for morphologica l, biochemical and molecular markers is relatively high. To investigat e whether part of this variation is the result of outcrossing, we desi gned RAPD analysis experiments to reveal both inter- and intra-accessi on crossing. No cases of inter-accession hybrids were documented, but an intra-accessional crossing rate of 0 to 4% was estimated for one of the four accessions studied. Therefore, a rare outcrossing event betw een local individuals and migrating genotypes may contribute to high g enetic variability observed in natural M. polymorpha. A better underst anding of the factors which influence outcrossing in M. polymorpha is pertinent both for medic breeding programmes and for assessing risks a ssociated with releasing transgenic herbicide-resistant crops.