Commercial guava orchards have been destroyed in the São Francisco river Valley, northeastern Brazil, by the Meloidogyne enterolobii nematode but to date no effective control has been identified. The objective of the present study was to obtain and assess interspecific hybrids between Psidium guajava × P. guineense for tolerance to M. enterolobii, for use as guava rootstock or in genetic studies. Crossings were made between P. guajava GUA 161 PE accession and the P. guineense ARA 138 RR and ARA 153 BA accessions. The crossings were made when the calyx ruptured on the flower buds, and two SSR microsatellite markers were used to confirm the hybridization. When the plants reached 15 to 20 cm in height, they were inoculated with a suspension containing 10,000 nematode eggs. Four months after inoculation, the soil was removed from the plants and individual evaluation was carried out for the number of galls, number of eggs and reproductive factor (RF). The plants in the two crossings were considered as hybrids when genotyped with the mPgCI 251 and mPgCI 252 loci. The 10 plants from the 161 PE × ARA 138 RR cross assessed were tolerant to the nematode, with gall index and RF equal to zero. Seven of the 10 plants of the GUA 161 PE × ARA 153 BA cross assessed were considered susceptible to the nematode. The results suggested variability for tolerance among P. guineense accessions and that tolerance to the nematode could be conferred by a dominant allele. Plants of the interspecific hybrid grew similarly to the guava trees at eight months of age in field and were highly compatible with 'Paluma' guava, indicating that this strategy can present excellent results in controlling M. enterolobii.

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.

Meloidogyne enterolobii (syn. M. mayaguensis) has been reported to cause severe damage in commercial guava orchards and other plants in Central and South American countries. Considering the risk of introduction and dissemination of this pest in the European region, M. enterolobii was placed on the EPPO A2 list in 2010. The use of non-host fruit species is a recommended strategy to manage rootknot nematodes in infested guava orchards. This study screened 89 plant genotypes from 25 fruit plants of economic importance, plus two susceptible controls (guava and tomato) for its host status to M. enterolobii. Three to eight months after inoculation, nematode reproduction factor (RF) was used to characterize host suitability of fruit crops to this nematode. Ten banana genotypes, six Barbados cherries, one fig, two grape rootstocks and six melons were rated as good hosts for this nematode. Sixteen fruit plants behaved either as non-hosts or poor hosts to M. enterolobii, including assaí, atemoya, avocado, cashew nut, citrus, coconut, grape, jabuticaba, mango, mulberry, papaya, passion fruit, sapodilla, soursop, starfruit and strawberry. For the future, field experiments in areas infested by this nematode are essential to confirm the greenhouse results. These non-host fruit species can replace in the future eradicated guava trees in fields severely infested by this nematode and become an economic option for growers where M. enterolobii is considered a serious problem.

The presence of the root-knot nematode, Meloidogyne enterolobii, in guava commercial orchards in many Brazilian states has caused severe loss to growers. 146 guava and araçazeiro (wild guava) accessions were evaluated in a greenhouse and nursery in order to find resistant accessions to be used as rootstock for commercial guava cultivars. In the greenhouse, 15 to 20 cm tall plants were inoculated with 10,000 nematode eggs, in a randomized complete design with an unequal number of replications. Under field nursery conditions, after seed germination, the plants were transferred to plastic bags with nematode contaminated soil. Five months after inoculation, the greenhouse accessions were evaluated for nematode damage. The nematode reproduction factor (RF) was estimated and the accessions classified as resistant or susceptible. The plants grown in the field nursery were visually evaluated for the presence of root galls one year after transplanting to plastic bags. A total of 66 Psidium, including 14 araçazeiro and 52 guava accessions, were evaluated under field nursery conditions. Two araçazeiros were classified as resistant, and another segregated for nematode tolerance under nursery conditions. All the guava accessions were susceptible in both evaluation conditions. Among the 20 araçazeiro accessions evaluated in the greenhouse, three were resistant to the nematode (RF<1) and 9, collected in the state of Rio Grande do Sul, were immune (RF=0). After further investigation performed among some resistant araçazeiro accessions collected in southern Brazil, subtropical region, poor plant development was observed in the northeastern Brazilian semi-arid region and low grafting compatibility with commercial guava cultivars. The current strategy to overcome this guava pest includes developing interspecific Psidium hybrids among resistant araçazeiros and susceptible guava to obtain hybrids with adequate plant height and stem diameter, highly compatible when used as rootstock for commercial guava cultivars.

Occurrence of Meloidogyne paranaensis in coffee plantations in the Alto Paranaíba region of Minas Gerais, BrazilCoffee (Coffea arabica) plantations showing symptoms of decline, with peeled and rough roots and fewer side rootlets were observed in the State of Minas Gerais, Brazil. Meloidogyne spp. females were obtained from the thicker roots and processed for