Close linkage between the Cf-2/Cf-5 and Mi resistance loci in tomato.

Analysis of restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD) markers in tomato plants segregating for resistance to the fungus Cladosporium fulvum was used to localize the resistance genes Cf-2 and Cf-5 to the same region of chromosome 6. This region, between GP79 and Aps-1, is the same as that reported for the Mi gene, which confers resistance to root-knot nematodes (meloidogyne spp.). Recombination values based on F2 populations from crosses between near-isogenic lines of L. esculentum 'Moneymaker' carrying Cf-2 or Cf-5 and Lycopersicon pennellii, indicate that this region occupies 4-5 centiMorgans (cM). However, in F2 populations from crosses between the L. esculentum stock LA1190 carrying yv and these lines, this value is 1-2 cM. The Cf-2 gene, introduced into L. esculentum from L. pimpinellifolium, is on an introgressed segment that extends from a point distal to GP79 to a point between TG232 and H2D1. The origin of Cf-5 was found to be L. esculentum var. cerasiforme rather than L. pimpinellifolium as previously reported. No RFLP markers and only one RAPD marker showed a polymorphism between Moneymaker and the near-isogenic line carrying Cf-5.