Isabel Luci Conceição

Kiwifruit (Actinidia spp.) has become a globally important crop, with A. chinensis var. deliciosa cv. Hayward being the most widely cultivated cultivar. Root-knot nematodes (RKNs, Meloidogyne spp.) are highly damaging plant parasites that are widespread in Portugal. Meloidogyne hapla predominates in the major production areas and occasionally co-occurs with M. arenaria and M. hispanica; however, the effects of these RKNs on kiwifruit performance and yield remain largely unclear. This study evaluated the reaction of Hayward and Tomuri cultivars to different Meloidogyne spp. and inoculum levels, focusing on plant–nematode interactions with distinct M. hapla populations. Kiwifruit’s reaction to RKN parasitism varied according to both the Meloidogyne spp. and the intraspecific variability of M. hapla. Meloidogyne arenaria and M. hispanica caused different impacts in kiwifruit cultivars. Intraspecific variation in M. hapla influenced the host reaction, with certain populations showing high parasitic rates. Gall numbers increased with M. hapla inoculum density, indicating that higher nematode populations intensify pressure on the host. Although few differences were observed between cultivars, M. arenaria had a greater impact on cv. Hayward (female), while M. hispanica affected cv. Tomuri (male) more strongly, showing the importance of investigating cultivar- and sex-specific responses to RKNs for effective management in kiwifruit. These findings highlight that susceptibility and tolerance in kiwifruit depend on the RKN species identity, intraspecific variability, population density and cultivar-specific responses, emphasizing the complexity of host–nematode interactions.

Plant-parasitic nematodes (PPN) remain one of the major constraints to global agricultural productivity, affecting numerous crops and contributing to substantial yield losses

Editorial: Genetics of plant-nematode interactions

Summary: Potato cyst nematodes (PCN), Globodera spp., cause damage to potatoes in more than 60 countries and several management strategies, including the application of chemical nematicides, are commonly used for their control. However, due to stringent regulations in Europe several nematicides have been, or are being, removed from the market due to their potential toxic effects on the environment and human health. New solutions and nematode management strategies are being sought to control these challenging and economically important nematodes. In this study, the effects of Salibro™, a novel sulfonamide nematicide based on the active ingredient fluazaindolizine (Reklemel™ active), were evaluated on the hatching, motility, infectivity and reproduction of PCN in the laboratory. Depending upon the duration of nematode pre-exposure, Salibro™ at concentrations of 5-250 mg fluazaindolizine (active substance) (a.s.) kg⁻¹ (equivalent to 5-250 ppm a.s.) affected hatching, motility and infectivity of second-stage juveniles of G. pallida and G. rostochiensis, whereas the reproduction of G. pallida was only influenced at 5-50 mg a.s. kg⁻¹. Salibro™, under laboratory conditions, has intrinsic activity against both PCN species and could be a promising additional tool for the integrated management of PCN. Further studies are needed to demonstrate Salibro™ efficacy under field conditions.

Summary: Root-knot nematodes (RKN), Meloidogyne spp., have a wide host range and are common in the Mediterranean area. Cultivated lavender (Lavandula angustifolia) was found naturally infested by M. hapla in Kozani area, the first documented infestation of this crop by RKN in Greece. Oxalis pescaprae, a common winter weed in Crete, was found to be a host of M. javanica under artificial inoculation. This weed acts as a potential winter host of the nematode in fields cultivated with vegetable crops. Two populations of M. ethiopica were found in kiwi and maize in Greece in the past. Recently, populations of M. ethiopica from Europe were re-classified as M. luci, based only on the population isolated from kiwi for Greece. In the current work, the RKN populations originating from kiwi and maize and maintained on tomato, were identified as M. luci. Nematode species identification was determined by electrophoretic analysis of protein extracts obtained from females.

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.