Isabel Luci Conceição

Solanum sisymbriifolium - a new approach for the management of plant-parasitic nematodes

Plant-parasitic nematodes are serious pests causing important crop losses worldwide. After extensive screening of non-tuber-bearing Solanaceae, a resistant trap crop, Solanum sisymbriifolium, with a high production level of hatching agents, seemed an ideal control method for potato cyst nematodes (PCN), Globodera spp. Recently, root-knot nematodes (RKN), Meloidogyne spp., were found coexisting with PCN. Therefore, it is important to find alternative methods to control both nematode genera. The chemical properties of S. sisymbriifolium turns this plant into an excellent candidate for further nematicidal studies and to develop new crop production models. Studies concerning the effects of this plant on plant-parasitic nematodes are presented. Pathogenicity studies with four S. sisymbriifolium cvs (Domino, Pion, Sis 4004 and Sharp) and five Meloidogyne species showed that all cultivars of S. sisymbriifolium studied were resistant to M. chitwoodi and hypersusceptible to M. arenaria and M. hapla. For M. hispanica only cv Pion was susceptible. M. javanica induced different responses: cvs Pion and Sharp were susceptible; cv Domino resistant and Sis 4004 hypersusceptible. The studies of the hatching effects of root exudates from these cvs showed that they had an influence on the hatching inhibition of second stage juveniles of the five Meloidogyne species tested.

Root-knot nematodes, Meloidogyne spp., on potato in Portugal

Root-knot nematodes (RKN), Meloidogyne spp., are among the most economically important nematodes in agriculture and can cause significant losses in potato (Solanum tuberosum L.), in both warm and cool climates, depending upon the nematode species (Brodie et al., 1993; Greco, 1993). RKN have not yet been recognised as serious nematode pests in the potato-growing areas of Portugal. However, during the past 10 years, nematode damage has been found in some areas and it is clear that infestation of potato fields by RKN is becoming more widespread. Some of the RKN species attacking potato, e.g., M. chitwoodi, also have quarantine status and one isolate originating from Portugal has already been included in a molecular study (Powers et al., 2005). The aim of this work was to provide data on the identification of Meloidogyne spp. on potato in Portugal. During a survey for potato cyst nematodes (PCN), Globodera spp., RKN isolates were detected in tubers and in soil collected in 210 potato fields in various districts of Portugal (Table 1). When tubers infected with RKN were detected, egg masses were collected and susceptible tomato plants (Solanum lycopersicum L.) cv. Easypeel were inoculated with ten egg masses/pot. When only soil samples were taken, tomato plants with four true leaves were transplanted into the original soil. All plants were maintained in a glasshouse at 25-30◦C. After 45 days, plants were uprooted, their roots gently washed free of soil and females, when present, collected with forceps under a stereomicroscope. Morphological characterisation was based on a minimum of 20 perineal patterns (Taylor & Netscher, 1974; Hartmann & Sasser, 1985). Their char-

Using RAPD markers to analyse genetic diversity in Portuguese potato cyst nematode populations

The two species of potato cyst nematodes (PCN) have different spectra of virulence towards host resistance genes and a proper identification is important in the control of these nematodes by means of resistant potato cultivars. Genetic variability of 32 populations of Globodera rostochiensis and three of G. pallida from different regions of Portugal were analysed and compared using random amplified polymorphic DNA and sixteen primers. In addition, a population of G. pallida (Luffness) from Scotland, UK, was included for comparison. The patterns obtained were evaluated using the Nei coefficient and the UPGMA cluster method. The resulting clusters were expressed as dendrograms in the Phylogeny Inference Package (PHYLIP) program. Separation of the two species of PCN was achieved with an average similarity of 43%. Two populations of G. rostochiensis (PT1 and PT82) appear to be distinct from the main group of this species. One population of G.pallida (PT104) was distinct from the others of this species and the Luffness population was linked most closely with PT5701. Distinct clusters were observed within both species but the clusters could not be related to the geographic proximity of the populations.

Detection of the root-knot nematode Meloidogyne ethiopica in Greece

Root-knot nematodes (RKN), Meloidogyne spp., are very significant in agriculture because they can be found almost everywhere and have a wide host range. In summer 2009, two soil samples from maize and kiwi crops, from the area of Kavalla in North Greece, were analyzed for the presence of nematodes. RKN were detected in both samples and identified as M. ethiopica on the basis of biochemical (esterases) and sequence data (18S rDNA). Meloidogyne ethiopica poses a significant threat to farmers in Greece and the establishment and spread of this species has to be controlled. This is the first report of M. ethiopica in Greece and the second report of this species for Europe.

Characterisation of potato cyst nematode populations from Portugal

Populations of potato cyst nematode (PCN) were assembled from all of the potato growing regions of Portugal, either by direct sampling of fields or from cyst samples sent to the University of Coimbra for identification. When 30 or more cysts were available, isoelectric focusing of species-specific protein bands was used to identify which PCN species were present. PCN was present in 35% of a set of 226 soil samples. PCN was also identified in a larger set of 423 populations. Of the 423 populations, 83% were pure Globodera rostochiensis, 8% were pure G. pallida and 9% were mixtures of the two. PCN was found in all of the main potato growing areas but G. pallida was not detected in Coimbra, Setubal or Viana do Castelo districts.

Assessment of the use of high-performance capillary gel electrophoresis to differentiate isolates of Globodera spp.

Capillary gel electrophoresis was used to characterise 49 Portuguese isolates of potato cyst nematodes, three of Globodera pallida and 46 of G. rostochiensis , and eight isolates representative of pathotypes defined for these two species (Ro1, Ro2, Ro3, Ro4 and Ro5 for G. rostochiensis and Pa1, Pa2 and Pa3 for G. pallida ). Protein extracts of four samples of 50 cysts per isolate were separated using a Beckman eCAP SDS 14-200 kit, in a capillary of 57 cm length and 100 μ m internal diameter and with a run time of 40 min. Reproducible protein profiles were obtained and the isolates were compared taking into account the relative migration time and area of each peak recorded by the Gold Software Data System (Beckman). Euclidian distances between isolates were calculated using peak area data and a dendrogram was constructed according to the UPGMA method. Portuguese isolates showed great variability and it seems that protein composition is not related to their geographic origin. Protein profiles of each pathotype were obtained and some of the proteins seem to be specific for each pathotype. However, despite their common reaction to the H1 resistance gene, Ro1 and Ro4 were not grouped together, and Pa1 was not grouped with Pa2.

Occurrence of a new resistant breaking pathotype of Meloidogyne incognita on tomato in Greece

In a pot assay, a population of Meloidogyne incognita from Northern Greece, reproduced on the resistant tomato cv. Silvana carrying the Mi gene and on three susceptible pepper cultivars. Its ability to reproduce on the resistant tomato and on pepper cv. California Wonder was sustainable for several generations. Till now, the only resistant breaking population of M. incognita on resistant tomato found in Greece was a distinct one from Crete which did not reproduce on susceptible pepper cultivars. Thus, the population of M. incognita from Northern Greece represents a new type of a resistant breaking pathotype, reported for the first time in the country, and a potential threat for both resistant tomato crops and susceptible peppers in the field.

An update on the occurrence of resistance-breaking populations of root-knot nematodes (Meloidogyne spp.) on resistant tomato in Greece with six new records from Crete

Summary The available published information on the occurrence of resistance-breaking populations of root-knot nematodes (Meloidogyne spp.) on resistant tomato in Greece is updated. Within the period 1994-2013, 13 populations (11 M. javanica and 2 M. incognita) able to reproduce on resistant tomato had been recorded in the regions of Crete, Epirus, Thrace, Peloponissos and Macedonia. In the present study six more resistance-breaking populations, four M. javanica and two M. incognita, were detected in the period 2013-2014, all originating from greenhouse vegetables in Crete. Four of these populations, two M. javanica and two M. incognita, originated from the region of Ierapetra. This is the first time that such populations are found in this major area of greenhouse vegetable production of Crete.