A high-throughput method for early screening of coffee (Coffea spp.) genotypes for resistance to root-knot nematodes (Meloidogyne spp.)

Root-knot nematodes (Meloidogyne spp.) threaten the livelihood of millions of farmers producing coffee worldwide. The use of resistant plants either as cultivars or rootstocks appears to be the single most effective method of control. A screening method was developed to evaluate large populations of plants for resistance to root-knot nematodes. Two coffee cultivars, one susceptible and the other resistant to Meloidogyne paranaensis, were grown under controlled conditions in two substrates: a commercial sieved potting compost and an inert substrate containing sand with a water-absorbent synthetic polymer. Plant growth and development and nematode multiplication were compared for two inoculation dates (2 and 8 weeks after planting) and two evaluation dates (eight and 13 weeks after inoculation). Root growth, but not nematode multiplication, was influenced by the choice of substrate. Evaluation of the differences in root weight and nematode numbers between the different cultivars, substrates and dates of inoculation suggested that an optimal condition could be defined. The best discrimination between susceptible and resistant plants was found in the experiment where inoculation occurred at 2 weeks after planting and evaluation occurred at 8 weeks after inoculation. Because the total duration of this experiment was only 3 months, high-throughput evaluation was possible, opening up new possibilities for screening large germplasm collections and studying the genetic control of root-knot nematode resistance in coffee