Meloidogyne enterolobii has been reported in some states of Brazil and other countries causing severe damage on commercial guava (Psidium guajava). The use of resistant varieties is the most effective way to manage nematode parasitism. This study screened 51 accessions of Psidium spp. selected from the Psidium Germplasm Collection (Embrapa) to look for resistance against M. enterolobii. Six months after inoculation, nematode reproduction factor (RF) was used to assess resistance. The following species were resistant to M. enterolobii: P. cattleianum (yellow guava), P. friedrichsthalianum (Costa Rican guava), Acca sellowiana (feijoa) and P. rufum (purple guava). All 43 wild accessions of P. guajava were susceptible, as well as three accessions of P. guineense (Brazilian guava), one of P. acutangulum (pear guava) and the susceptible control P. guajava cv. Paluma. When used as rootstocks under greenhouse conditions, P. cattleianum and P. friedrichsthalianum were compatible with cv. Paluma; however, in greenhouse and field conditions only 50% of both scions survived. No apparent hypersensitive response (HR) was seen in the resistant guava P. cattleianum and P. friedrichsthalianum. Juveniles were able to develop normal feeding sites similar to those in susceptible roots 6-13 days after inoculation (dai). From 27 to 32 dai, giant cell deterioration was observed and nematodes showed arrested development. The majority of nematodes failed to reach maturity and did not begin laying eggs in resistant roots. These results suggested that the induction of resistance is relatively late in this pathosystem.

RESUMOMeloidogyne mayaguensis foi detectado pela primeira vez no estado de Goiás, em duas propriedades (Formosa e Luziânia), causando dano em pomares comerciais de goiaba (Psidium guajava) cv. Paluma de um ano de idade e de 14 anos, respectivamente. Plantas infectadas pelo nematóide mostraram redução de crescimento, clorose generalizada, deficiência nutricional e redução qualitativa e quantitativa de produção. As raízes severamente infestadas apresentaram-se pouco desenvolvidas e deformadas pela presença de múltiplas galhas de tamanho variado. Mamoeiros (Carica papaya) cv. Formosa, plantados em consórcio com as goiabeiras na propriedade de Formosa, apresentaram numerosas galhas no sistema radicular, embora, nenhum sintoma secundário de meloidoginose tenha sido observado na parte aérea. A produção de frutos dos mamoeiros foi alta, evidenciando tolerância dessa cultivar ao nematóide. O fenótipo M2 para a isoenzima esterase (Rm: 0,7, 0,9) foi detectado e M. mayaguensis identificado em ambas as culturas e propriedades. As análises com marcadores moleculares espécie-específica usando primers que amplificam regiões intergênicas do DNA ribossomal e do DNA mitocondrial também confirmaram esse diagnóstico. Levantamento realizado, em outras localidades da fazenda em Formosa mostrou a presença de Meloidogyne javanica em baixa população, corroborando a idéia de introdução de M. mayaguensis na área, através do plantio de mudas infectadas, oriundas da região de Petrolina. Na propriedade em Luziânia, o nematóide é provavelmente de ocorrência natural, considerando-se a idade das plantas e o número reduzido de goiabeiras infectadas. Palavras-chave: fenótipo de esterase, DNA ribossômico, DNA mitocondrial, identificação, nematóide das galhas. ABSTRACT Detection of Meloidogyne mayaguensis on guava and papaya in Goiás State of Brazil using molecular markersMeloidogyne mayaguensis was reported for the first time in the State of Goiás (Formosa and Luziânia), causing damage in oneyear old and 14 year-old commercial guava (Psidium guajava) cv. Paluma orchards. Plants infected by the nematode showed symptoms such as stunted growth, general chlorosis, nutrient deficiency and consequent decline in yield quality and quantity. Severely infested root systems were poorly developed, distorted by small and large multiple galls and devoid of fine roots. Plants of papaya cv. Formosa were cultivated in consortium with guava in the Formosa orchard and presented several galls in the root system, but no root-knot-nematode root-knot-nematode secondary symptoms were observed in the aerial part. The production of papaya fruits was high, evidencing tolerance of this cultivar to the symptoms were observed in the aerial part. The production of papaya fruits was high, evidencing tolerance of this cultivar to the were observed in the aerial part. The production of papaya fruits was high, evidencing tolerance of this cultivar to the nematode. The M2 phenotype (Rm: 0.7, 0.9) was detected for the isoenzyme esterase and M. mayaguensis was identified in both 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 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.