Root-Knot Nematode Species Associated with Horticultural Crops in the Island of Azores, Portugal

Plant-parasitic nematodes (PPN) are an economically important group of plant pests present throughout the world. In particular, root-knot nematodes (RKN), sedentary endoparasites of a wide variety of economically important hosts with the ability to survive in temperate regions. During 2020–2021 an extensive survey of Meloidogyne spp. was undertaken on the island of São Miguel Azores, Portugal. A total of 80 samples comprising 23 species of plants were collected from 13 localities in 4 districts of the island. Samples included field and greenhouse vegetable crops. Bioassays were carried out to obtain females and juveniles for morphological and biochemical characterization of the isolates. The observed morphological features showed high similarity and consistency with previous descriptions of the genus. Concerning the biochemical characterization, the esterase (EST) phenotype displayed the patterns described for M. incognita, M. arenaria, and M. javanica. Meloidogyne incognita was found to be the most prevalent species with respect to both natural host range and geographical distribution, followed by M. arenaria and M. javanica. This is the first field survey that assesses the species of root-knot nematodes associated with horticultural crops in the Azores Island, contributing additional information on the distribution of this genusinfo:eu-repo/semantics/publishedVersio

Potato Cyst Nematodes: geographical distribution, phylogenetic relationships and integrated pest management outcomes in Portugal

The identification and phylogenetic relationships of potato cyst nematodes (PCN) were studied to assess the potential value of geographical distribution information for integrated pest management of potato production in Portugal. This research focused on PCN species, Globodera pallida and Globodera rostochiensis. From 2013 until 2019, 748 soil samples from the rhizosphere of different potato cultivars were surveyed in the Portuguese mainland to detect and identify both species and track their location. PCN are widespread invasive species throughout Portugal. In fact, during the survey period an incidence of 22.5% was estimated for the tested samples. The patterns of infestation vary among regions, increasing from south to north, where PCN were first detected. Currently, both species are present in all potato producing regions of the country, with a greater incidence of G. pallida. Phytosanitary control measures are influencing to the observed results. The use of potato cultivars resistant to G. rostochiensis led to a decrease of this species but had no influence on G. pallida detections, which continues its reproduction freely since there are no effective resistant cultivars for this species. The relationship between the presence, infestation rate, spread and geographical distribution of PCN is discussed in terms of behavioral responses of the potato cultivars and the implications for developing new integrated crop protection measures

Nemátode-dos-citrinos: prevenir o declínio lento do pomar

Os citrinos são as fruteiras mais importantes em termos de produção a nível mundial, com cerca de 130 milhões de toneladas produzidas (World Citrus Organisation, 2020), repartin- do-se por mais de 125 países localizados entre os 40° de latitude a norte e a sul do Equador. Entre as várias ameaças à produção citrícola contam-se os nemátodes fitoparasitas. Os nemátodes fitoparasitas são pequenos animais, de aspeto vermiforme, cilíndricos e alongados, geralmente com menos de 1-2 mm de comprimento, que causam doenças às plantas. A maior parte habita no solo, infe- tando as raízes de onde se alimentam atra- vés do estilete (estrutura na cavidade oral que funciona como uma agulha hipodérmi- ca, sugando o conteúdo das células vegetais). Uns permanecem no exterior (ectoparasi- tas), enquanto outros penetram nas raízes (endoparasitas) e outros ainda avançam nos tecidos do hospedeiro, mas só com a parte posterior (cabeça e pescoço), permanecendo o restante corpo fora da raiz (semiendopara- sitas). O nemátode-dos-citrinos, Tylenchulus semipenetrans, é um semiendoparasita e daí a sua designação específica. De todos os ne- mátodes que podem afetar estas fruteiras, é aquele que tem maior impacte económico, sendo a única espécie presente em todas as regiões produtoras de citrinos do mundo

Bioactivity of Monoterpene Alcohols as an Indicator of Biopesticidal Essential Oils against the Root Knot Nematode Meloidogyne ethiopica

The application of pesticides remains one of the most efficient control methods for phytophagous parasites in crops. Essential oils (EOs) are complex mixtures of highly active compounds that can be used as biopesticides against plant parasitic nematodes. In the present work, the antinematodal activity of the monoterpene alcohols geraniol, linalool, menthol or  -terpineol, which are generally found in high amounts in EOs of some aromatic and medicinal plants, was analyzed on the root knot nematode Meloidogyne ethiopica. Geraniol showed intense and lasting antinematodal activity, suggesting that EOs rich in this compound can be used in the development of nematicidal biopesticides to integrate sustainable pest management strategies against this pest

Description of Longidorus bordonensis sp. nov. from Portugal, with systematics and molecular phylogeny of the genus (Nematoda, Longidoridae)

The genus Longidorus currently comprises 176 species of polyphagous plant ectoparasites, including eight species that vector nepoviruses. Longidorus is one of the most difficult genera to accurately identify species because of the similar morphology and overlapping measurements and ratios among species. Sequences of ribosomal RNA (rRNA)-genes are a powerful level-species diagnostic tool for the genus Longidorus. From 2015 to 2019, a nematode survey was conducted in vineyards and agro-forest environments in Portugal. The populations of Longidorus spp. were characterized through an integrative approach based on morphological data and molecular phylogenetic analysis from rRNA genes (D2-D3 expansion segments of the 28S, ITS1, and partial 18S), including the topotype of L. vinearum. Longidorus bordonensis sp. nov., a didelphic species recovered from the rhizosphere of grasses, is described and illustrated. Longidorus vineacola, with cork oak and wild olive as hosts, is also characterized. This is the first time that L. wicuolea, from cork oak, is reported for Portugal. Bayesian inference (BI) phylogenetic trees for these three molecular markers established phylogenetic relationships among the new species with other Longidorus spp. Phylogenetic trees indicated that i) L. bordonensis sp. nov. is clustered together with other Longidorus spp. and forms a sister clade with L. pini and L. carpetanensis, sharing a short body and odontostyle length, and elongate to conical female tail, and ii) all the other species described and illustrated are phylogenetically associated, including the topotype isolate of L. vinearum

The fight against plant-parasitic nematodes: current status of bacterial and fungal biocontrol agents

Plant-parasitic nematodes (PPNs) are among the most notorious and underrated threats to food security and plant health worldwide, compromising crop yields and causing billions of dollars of losses annually. Chemical control strategies rely heavily on synthetic chemical nematicides to reduce PPN population densities, but their use is being progressively restricted due to environmental and human health concerns, so alternative control methods are urgently needed. Here, we review the potential of bacterial and fungal agents to suppress the most important PPNs, namely Aphelenchoides besseyi, Bursaphelenchus xylophilus, Ditylenchus dipsaci, Globodera spp., Heterodera spp., Meloidogyne spp., Nacobbus aberrans, Pratylenchus spp., Radopholus similis, Rotylenchulus reniformis, and Xiphinema index

Parasitismo no nemátode da madeira do pinheiro – Estudo dos mecanismos de regulação de genes para o controlo da doença.

A Fileira do Pinho representou, em 2020, 80% dos postos de trabalho e 45% do volume de negócios nas indústrias florestais, assim como mais de 3% das exportações nacionais de bens. Há, no entanto, um défice de 2,3Mm3 de madeira de pinho que é justificado pelo fogo e a presença do nemátode da madeira do pinheiro (NMP), Bursaphelenchus xylophilus (Centro PINUS, 2021) (Figura 1). A doença da murchidão do pinheiro, causada pelo NMP, é considerada uma ameaça para as florestas de pinheiros em todo o mundo e a sua rápida disseminação nos países aonde foi detetada tem causado um grande impacte ao nível da sustentabilidade dos sistemas agroflorestais e de perda de biodiversidade. Uma vez que a mortalidade do pinheiro-bravo causada pelo NMP e a rápida propagação da doença podem ser exponenciadas pela combinação de condições climáticas, como a seca e as temperaturas mais elevadas, prevê-se que a frequência e propagação da doença será cada vez maior, nos pinhais aonde já existe, e ameace aqueles ainda não afetados existentes na região mediterrânica

NEMÁTODES DE QUISTO DA BATATEIRA – O USO DE VARIEDADES RESISTENTES COMO ESTRATÉGIA DE CONTROLO

Potato cyst nematodes (PCN), Globodera rostochiensis and G. pallida, are considered harmful quarantine organisms and can be devastating to potato fields if not controlled in a timely manner. Its designation derives from the fact that the female body, after their death, turns into a spherical cyst con- taining the eggs, which are protected from adverse conditions even in the absence of hosts. PCN are present in all potato pro- ducing regions of the country, including the Madeira and Azores islands. PCN control involves their opportune detection, cor- rect identification and appropriate control measures. Tests already carried out proved that the use of resistant varieties is effective for the management of these organisms. However, there is insufficient choice of par- tially resistant cultivars for growers, espe- cially for the control of G. pallida

PineEnemy - Exploring the NEmatode-MYcobiota interactions in Pine Wilt Disease

Pine wilt disease (PWD) is one of the most important threats to conifer forests in Europe [1] and worldwide [2], causing severe economic and environmental damages. This complex disease results from the interaction between three biological elements: the pathogenic agent Bursaphelenchus xylophilus, also known as pinewood nematode (PWN); the insect-vector (cerambycid beetles of the genus Monochamus) [3], and the host tree, mostly from Pinus spp. [4]. In 1999, B. xylophilus was firstly identified in maritime pines (Pinus pinaster) in Portugal and in Europe [1, 5]. Despite a nationwide monitoring system, enforcement of strict phytosanitary measures and constraints implemented after PWN detection, this devastating problem has spread quickly in Portuguese mainland, Madeira Island [5] and Northern Spain [6]. As a migratory endoparasite, once inside susceptible tree, PWN has the ability to feed on the living parenchyma of the epithelial cells in the resin canals, causing a reduction in water flux and ultimately cessation of resin flow. In the later stages of the disease, PWN assumes a mycetophagous phase. The development of the PWN population appears to be strongly associated with fungi that colonize the declining trees [3]. Fungi harboured in weakened pines are seen as essential for the ongoing development and completion of the PWN life-cycle, affecting not only PWN reproduction [8] but also the number of individuals carried by the insect-vector [9-10]. Through a spatio-temporal analysis, PineEnemy will focus on the characterization of the structure and dynamics of the nematode-fungi interactions through culturable and non-culturable approaches with special emphasis in metagenomics analysis. Our aim is to understand if PWN-associated mycobiota plays a key-role in the development of PWD, in interaction with PWN and insect-vector, and into which extend can be targeted to disrupt the disease cycle