First pathogenicity study of Hippeastrum sp. cultivars for the root-knot nematode Meloidogyne enterolobii.

Amaryllis (Hippeastrum sp.) is an important ornamental plant, yet information on its interaction with phytonematodes, especially with the aggressive and emerging root-knot nematode Meloidogyne enterolobii, remains scarce. This study evaluated, under controlled greenhouse conditions, the reaction of two amaryllis cultivars to M. enterolobii. Two experiments were conducted using Hippeastrum cv. Red Bull (experiment 1) and Hippeastrum cv. Orange Sovereign (experiment 2). Bulbs were inoculated with 0 (control), 10,000, 20,000 and 40,000 eggs and juveniles of M. enterolobii. Plant growth parameters, including fresh belowground biomass (FBB), fresh shoot biomass (FSB) and the reproduction factor of M. enterolobii (RF) were evaluated. Nematodes failed to establish on either Hippeastrum cultivars (RF < 1), indicating that both cultivars behave as inadequate hosts, yet nematode parasitism reduced plant growth parameters. The Red Bull cultivar presented a 30% reduction in FBB when inoculated with a population dose of 40,000 nematodes, exhibiting symptoms of intolerance to high inoculum densities in M. enterolobii infections. The Orange Sovereign cultivar, even though it showed a tendency towards a reduction in FBB and FSB, this reduction was not significant, and the plants were classified as resistant. This is the first study reporting the parasitic behavior of M. enterolobii in Hippeastrum cultivars.