Effect of the Mi Gene in Tomato on Reproductive Factors of Meloidogyne chitwoodi and M. hapla


  • C. R. Brown
  • H. Mojtahedi
  • G. S. Santo
  • V. M. Williamson


The effect of the Mi gene on the reproductive factor of Meloidogyne chitwoodi and M. hapla, major nematode pests of potato, was measured on nearly isogenic tomato lines differing in presence or absence of the Mi gene. The Mi allele controlled resistance to reproduction of race 1 of M. chitwoodi and to one of two isolates of race 2. No resistance to race 3 of M. chitwoodi or to M. hapla was found. Variability in response to isolates of race 2 may reflect diversity of virulence genotypes heretofore undetected. Resistance to race 1 of M. chitwoodi could be useful in potato if the Mi gene were functional following transferral by gene insertion technology into potato. Since the Mi gene is not superior to R[subM][subc][sub1] derived from Solarium bulbocastanum, the transferral by protoplast fusion appears to offer no advantage. Key words: Columbia root-knot nematode, isogenic lines, Meloidogyne chitwoodi, Meloidogyne hapla, nematode, northern root-knot nematode, potato, reproductive factor, resistance, tomato.