Towards the map based cloning of a recessive Fusarium resistance determinant from diploid Medicago sativa

A monogenic recessive Fusarium resistance determinant was identified in a diploid Medicago sativa population. The Fusarium susceptible and resistant phenotypes of the individuals in an F2 segregation population was inferred from a biological test using injured root test. The resulting phenotypes were used to position the Fusarium resistance determinant on linkage group 6 of the Medicago sativa genetic map. Using the DNA based molecular markers genome walk was initiated from both sides of the genetic region constructing two contigs which are about 0.5 centiMorgan (∼500 kilobasepairs) apart. The introduction of this genetic determinant into tetraploid alfalfa cultivars was unsuccessful since only triploid and pentaploid hybrids could be recovered from the 4×-2× crosses. The isolation of the gene and establishment of the function of this recessive Fusarium determinant is under progress.