Major Guava Nematodes and Control Prospects Using Resistance on Psidium Spp. And Non-Host Crops

Abstract

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 nonhost 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.

Resistant accessions of wild Psidium spp. to Meloidogyne enterolobii and histological characterization of resistance

“…identification, only M. enterolobii was detected in guava in Brazil (Siqueira et al, 2009). Carneiro et al (2012) found that P. guajava was a good host for M. enterolobii and a non-host for M. arenaria, M. incognita and M. javanica. Rossi et al (2002) observed similar results when three commercial guava cultivars were inoculated with M. incognita race 2 and M. javanica.…”

“…enterolobii has been misidentified in a number of surveys. It is probable that the severe root‐knot problem on guava in the Americas and the isolated cases in Africa and Asia involve only this particularly virulent species (Carneiro et al ., ).…”

“…in Psidium spp. have been carried out, including one grafting assay; however, in the majority, either the nematode was not identified as M. enterolobii (Carneiro et al ., ) or the rootstocks were misidentified. In a previous study, P .…”

“…Because of its morphological resemblance to M. incognita and M. arenaria when only the perineal patterns are considered Brito et al, 2004), M. enterolobii has been misidentified in a number of surveys. It is probable that the severe root-knot problem on guava in the Americas and the isolated cases in Africa and Asia involve only this particularly virulent species (Carneiro et al, 2012).…”

“…in Psidium spp. have been carried out, including one grafting assay; however, in the majority, either the nematode was not identified as M. enterolobii (Carneiro et al, 2012) or the rootstocks were misidentified. In a previous study, P. cattleianum was resistant (reproduction factor, RF, = 0) and P. friedrichsthalianum moderately resistant (RF = 1Á9) to M. enterolobii (Carneiro et al, 2007).…”