Major guava nematodes and control prospects using resistance on Psidium spp. and non-host crops

The worst nematode problem affecting guava is that created by root-knot nematode, which is a recognized limiting factor in commercial guava production in Central and South America. Considering the difficulty of identifying Meloidogyne enterolobii (=M. mayaguensis) only by the perineal pattern, this species has been misidentified in different regions around the world and identified frequently as M. incognita or Meloidogyne spp. The species’ identification is possible using esterase phenotype and molecular markers. Using these techniques, only M. enterolobii was detected on guava in Brazil, confirming the incorrect identification. The intraspecific genetic variability of 16 M. enterolobii isolates from different geographical regions and hosts were analysed with different neutral molecular markers (RAPD, ISSR and AFLP) and showed a high level of homogeneity among the populations. Considering the low variability among M. enterolobii isolates, genetic resistance could be considered the most effective method of control, but only one accession of P. friedrichstalianium (Costa Rican wild guava) was resistant and compatible as rootstock with P. guajava ‘Paluma’, in field conditions. Although this root-knot nematode displays a very wide host range, studies showed that crop rotation is possible for cleaning areas infested with the nematode, using 35 antagonistic plants. Some cultivars of corn are also very promising for use in reducing populations of M. enterolobii in infested fields. Fourteen fruit trees are non-host to M. enterolobii and only four fruit trees are good hosts. Considering the impossibility of cultivating guava in fields infested by M. enterolobii, crops presented as non-hosts or poor hosts could be used by the growers, but more studies should be done in the field, in infested areas, to support the results obtained in greenhouse conditions.