Seeds and plants of wild type Lupinusalbus are bitter and contain high level of alkaloids.During domestication, at least three genes conferringlow-alkaloid content were identified and incorporatedinto commercial varieties. Australian lupinbreeders exclusively utilize one of these sweetnessgenes, ‘‘pauper’’, in all varieties to prevent possiblebitterness contamination via out-crossing. A crosswas made between a sweet variety Kiev Mutant(containing pauper gene) and a bitter type landraceP27174, and the population was advanced into F8recombinant inbred lines (RILs). Twenty-fourplants representing sweetness and bitterness weresubjected to DNA fingerprinting by the microsatellite-anchored fragment length polymorphism(MFLP) technique. A dominant polymorphism wasdiscovered in an MFLP fingerprint. The MFLPmarker was converted into a co-dominant, sequencespecific,simple PCR-based marker. Linkage analysisby the software program MapManager withmarker score data and alkaloid phenotyping datafrom a segregating population containing 190 F8RILs indicated that the marker is linked to thepauper gene at the genetic distance of 1.4 centi-Morgans (cM). This marker, which is designatedas ‘‘PauperM1’’, is capable of distinguishing thepauper gene from the other two low-alkaloid genesexiguus and nutricius. Validation on germplasmfrom the Australian lupin breeding program showedthat the banding pattern of the marker PauperM1 isconsistent with the alkaloid genotyping on a widerange of domesticated varieties and breeding lines.The PauperM1 marker is now being implementedfor marker assisted selection in the Australian albuslupin breeding program.