Genes induced during early response to Meloidogyne incognita in roots of resistant and susceptible alfalfa cultivars.

A cDNA library made to RNA from roots of Meloidogyne incognita (root-knot nematode) susceptible alfalfa cv. Lahontan seedlings 72 h after root-knot nematode inoculation was differentially screened with cDNA made from uninoculated control and M. incognita infested (72 h) root RNA. Of the six cDNAs isolated, the deduced amino acid sequences of four showed significant homology to sequences present in the databank, while two were pioneer sequences. The four cDNAs with matches to known sequences include those for glycine-rich protein, the gluconeogenic pathway enzyme phosphoenolpyruvate carboxykinase, an isoflavone reductase-like protein, and metallothionein. We have followed the expression of these genes during the course of nematode infection in both the susceptible and resistant host and also in different plant organs. Based on these analyses, the genes induced early in nematode infection are related either to metabolic pathways or to stress/defense.