Screening of Tagetes patula L. on different populations of Meloidogyne

The response of the marigold species Tagetes patula L. against four 4 populations of Meloidogyne arenaria, 13 of M. hapla, three 3 of M. javanica and 46 of M. incognita from Spain and Uruguay was studied to evaluate their resistance to root-knot nematodes and support decisions on their agronomic management. The races and virulence groups of each Meloidogyne species was determined and the resistance of marigold characterized. T. patula was resistant to all M. arenaria, M. javanica and M. incognita populations, whereas M. hapla populations varied in their ability to parasitize marigold depending on the race. T. patula was resistant to one of the two populations of M. hapla race A and susceptible to the other one, but with a very low galling index and poor egg mass production, as well as susceptible to all the M. hapla race B populations, with a broad range of galling indices. Although no differences on response to marigold were observed among the virulence groups of M. incognita, the differential behaviour of populations among and within races A and B of M. hapla show that effective agronomic decisions should rely on the screening of the M. hapla population against which T. patula is going to be used. Future studies are needed to establish the nature of the resistant response of T. patula to root-knot nematodes.