Resource utilization and trophic position of nematodes and harpacticoid copepods in and adjacent to Zostera noltii beds

This study examines the resource use and trophic position of nematodes and harpacticoid copepods at the genus/species level in an estuarine food web in Zostera noltii beds and in adjacent bare sediments using the natural abundance of stable carbon and nitrogen isotopes. Microphytobenthos and/or epiphytes are among the main resources of most taxa, but seagrass detritus and sediment particulate organic matter contribute as well to meiobenthos nutrition, which are also available in deeper sediment layers and in unvegetated patches close to seagrass beds. A predominant dependence on chemoautotrophic bacteria was demonstrated for the nematode genus Terschellingia and the copepod family Cletodidae. A predatory feeding mode is illustrated for Paracomesoma and other Comesomatidae, which were previously considered first-level consumers (deposit feeders) according to their buccal morphology. The considerable variation found in both resource use and trophic level among nematode genera from the same feeding type, and even among congeneric nematode species, shows that the interpretation of nematode feeding ecology based purely on mouth morphology should be avoided

Tomato Response to Fusarium spp. Infection under Field Conditions: Study of Potential Genes Involved

Tomato is one of the most important horticultural crops in the world and is severely affected by Fusarium diseases. To successfully manage these diseases, new insights on the expression of plant– pathogen interaction genes involved in immunity responses to Fusarium spp. infection are required. The aim of this study was to assess the level of infection of Fusarium spp. in field tomato samples and to evaluate the differential expression of target genes involved in plant–pathogen interactions in groups presenting different infection levels. Our study was able to detect Fusarium spp. in 16 from a total of 20 samples, proving the effectiveness of the primer set designed in the ITS region for its detection, and allowed the identification of two main different species complexes: Fusarium oxysporum and Fusarium incarnatum-equiseti. Results demonstrated that the level of infection positively influenced the expression of the transcription factor WRKY41 and the CBEF (calcium-binding EF hand family protein) genes, involved in plant innate resistance to pathogens. To the best of our knowledge, this is the first time that the expression of tomato defense-related gene expression is studied in response to Fusarium infection under natural field conditions. We highlight the importance of these studies for the identification of candidate genes to incorporate new sources of resistance in tomato and achieve sustainable plant disease management.This research was supported by projects “Development of a new virus-based vector to control TSWV in tomato plants” with the references ALT20-03-0145-FEDER-028266 and PTDC/ASP-PLA/28266/2017, and “Control of olive anthracnose through gene silencing and gene ex- pression using a plant virus vector” with the references ALT20-03-0145-FEDER-028263 and PTDC/ASP- PLA/28263/2017, both projects co-financed by the European Union through the European Regional Development Fund, under the ALENTEJO 2020 (Regional Operational Program of the Alentejo), ALGARVE 2020 (Regional Operational Program of the Algarve) and through the Foundation for Science and Technology (FCT), in its national component. M.P. was supported by Portuguese National Funds through FCT/MCTES, under the PhD scholarship SFRH/BD/145321/2019, co-financed by the European Social Fund through the Regional Operational Program of the Alentejo. J.A.R. was supported by Portuguese National Funds through Project ALT20-03-0246-FEDER-000056, “BIOPRO- TOMATE: Bioproteção do tomateiro contra a fusariose—impacto das práticas agronómicas”, under scholarship BI_MESTRE_Uevora_CER_BIOPROTOMATE, co-financed by the European Regional Development Fund through Regional Operational Program Alentejo 2020

Defense Strategies: The Role of Transcription Factors in Tomato–Pathogen Interaction

Tomato, one of the most cultivated and economically important vegetable crops throughout the world, is affected by a panoply of different pathogens that reduce yield and affect product quality. The study of tomato–pathogen system arises as an ideal system for better understanding the molecular mechanisms underlying disease resistance, offering an opportunity of improving yield and quality of the products. Among several genes already identified in tomato response to pathogens, we highlight those encoding the transcription factors (TFs). TFs act as transcriptional activators or repressors of gene expression and are involved in large-scale biological phenomena. They are key regulators of central components of plant innate immune system and basal defense in diverse biological processes, including defense responses to pathogens. Here, we present an overview of recent studies of tomato TFs regarding defense responses to biotic stresses. Hence, we focus on different families of TFs, selected for their abundance, importance, and availability of functionally well-characterized members in response to pathogen attack. Tomato TFs’ roles and possibilities related to their use for engineering pathogen resistance in tomato are presented. With this review, we intend to provide new insights into the regulation of tomato defense mechanisms against invading pathogens in view of plant breeding.This work was funded by the projects “Development of a new virus-based vector to control TSWV in tomato plants” with the references ALT20-03-0145-FEDER-028266 and PTDC/ASP-PLA/28266/2017, and “Control of olive anthracnose through gene silencing and gene expression using a plant virus vector” with the references ALT20-03-0145-FEDER-028263 and PTDC/ASP-PLA/28263/2017, co-financed by the European Union through the European Regional Development Fund, under the ALENTEJO 2020 (Regional Operational Program of the Alentejo), ALGARVE 2020 (Regional Operational Program of the Algarve) and through the Foundation for Science and Technology (FCT), in its national component. M.P. was supported by Portuguese National Funds through FCT/MCTES, under the PhD scholarship SFRH/BD/145321/2019, co-financed by the European Social Fund through the Regional Operational Program of the Alentejo. This work was also supported by National Funds through FCT under the Project UIDB/05183/2020

Co infection of OMMV and OLV-1 enhances symptoms and increases both viruses accumulation and viral derived siRNAs in plants

Previous extensive field surveys in olive orchards have revealed high levels of Olive mild mosaic virus (OMMV) and Olive latent virus 1 (OLV-1), frequently appearing in mixed infections. These viruses belong to genus Alphanecrovirus and their RNA dependent RNA polymerase (RdRp),as well as their p6 and p8 amino acid sequences share over 87% identity

Metagenomic Assessment Unravels Fungal Microbiota Associated to Grapevine Trunk Diseases

Grapevine trunk diseases (GTDs) are among the most important problems that affect the longevity and productivity of vineyards in all the major growing regions of the world. They are slow-progression diseases caused by several wood-inhabiting fungi with similar life cycles and epidemiology. The simultaneous presence of multiple trunk pathogens in a single plant together with the inconsistent GTDs symptoms expression, their isolation in asymptomatic plants, and the absence of effective treatments make these diseases extremely complex to identify and eradicate. Aiming to gain a better knowledge of GTDs and search sustainable alternatives to limit their development, the present work studied the fungal community structure associated with GTDs symptomatic and asymptomatic grapevines, following a metagenomic approach. Two important cultivars from the Alentejo region with different levels of susceptibility to GTDs were selected, namely, ‘Alicante Bouschet’ and ‘Trincadeira’. Deep sequencing of fungal-directed ITS1 amplicon led to the detection of 258 taxa, including 10 fungi previously described as responsible for GTDs. Symptomatic plants exhibited a lower abundance of GTDs-associated fungi, although with significantly higher diversity of those pathogens. Our results demonstrated that trunk diseases symptoms are intensified by a set of multiple GTDs-associated fungi on the same plant. The composition of fungal endophytic communities was significantly different according to the symptomatology and it was not affected by the cultivar. This study opens new perspectives in the study of GTDs-associated fungi and their relation to the symptomatology in grapevines.This research was supported by Portuguese National Funds through FCT- MCTES under the PhD scholarship SFRH/BD/145321/2019, attributed to M.P., co-financed by the European Social Fund through the Regional Operational Program of the Alentejo. It was also supported by the project “Control of olive anthracnose through gene silencing and gene expression using a plant virus vector” (ALT20-03-0145-FEDER-028263 and PTDC/ASP-PLA/28263/2017) and by the project “Development of a new virus-based vector to control TSWV in tomato plants” (ALT20-03- 0145-FEDER-028266 and PTDC/ASP-PLA/28266/2017), both projects co-financed by the European Union through the European Regional Development Fund, under the Alentejo 2020, Algarve 2020 and through the FCT, in its national component

Benthic nematode assemblage composition and diversity during a natural recovery process of Zostera noltii seagrass beds,

In 2008, the stable seagrass beds of the Mira estuary (SW Portugal) disappeared completely; however, during 2009, they have begun to present early symptoms of natural recovery, characterised by a strongly heterogeneous distribution. This study was designed to investigate the spatial and temporal variability patterns of species composition, densities and trophic composition of the benthic nematode assemblages in this early recovery process, at two sampling sites with three stations each and at five sampling occasions. Because of the erratic and highly patchy seagrass recovery and the high environmental similarity of the two sampling sites, we expected within-site variability in nematode assemblages to exceed between-site variability. However, contrary to that expectation, whilst nematode genus composition was broadly similar between sites, nematode densities differed significantly between sites, and this between-site variability exceeded within-site variability. This may be linked to differences in the Zostera recovery patterns between both sites. In addition, no clear temporal patterns of nematode density, trophic composition and diversity were evident

Enzymatic activity on sediments and nematode assemblage responses during seagrass beds habitat recovery following the disturbance of the traditional digging activity of bivalves harvesting.

Sediment digging is an anthropogenic activity connected to the exploitation of living resources in estuarine and marine environments. The knowledge on the functional responses of the benthic assemblages to the physical disturbance is an important baseline to understand the ecological processes of the habitat recovery and restoration and to develop tools for the management of the harvesting activities. To investigate the effects of the digging activity of the bivalves on Zostera noltii seagrass beds a manipulative field experiment was conducted that included the enzymatic activity of sediments and the associated nematode assemblages. Four plots (two undisturbed serving as control and two dug to collect bivalves - treatment) with 18 subplots were randomly located at seagrass beds in the Mira estuary at the SW coast of Portugal. Samples were randomly and unrepeatably collected from three subplots of each plot in five different occasions, before sediment digging (T0) up to six months after disturbance (T5). Microbial activity in sediments was assess by determining the extracelular enzymatic activity of six hydrolytic enzymes (sulfatase, phosphatase, b -N-acetilglucosaminidase, b-glucosidase, urease, protease) and two oxidoreductases (phenol oxidase and peroxidase). The microbial community status was also assessed through the measurement of dehydrogenase, which reflects microbial respiration. The nematode assemblages composition, biodiversity and trophic composition at different sampling occasions were also analyzed. The fluorometric and biochemical parameters analysed of the Z. noltii plants during the experimental period showed a recovery of the seagrass beds, and it was detected an increase of the enzymatic activity of the sediments after disturbance. The nematodes assemblages were similar in all sampling occasions. The seagrass beds and the nematodes assemblages associated showed a high resilience to the stress caused by the traditional bivalves digging activity. The obtained results allow the development of a management programme for the commercial fishing activity to maintain the good environmental status and minimized the secondary environmental effects on marine and estuarine habitats through the establishment of a baseline for the regulation of the harvesting frequency

Occurrence of Fusarium proliferatum Causing Vascular Wilt on Cowpea (Vigna unguiculata) in Brazil

Cowpea (Vigna unguiculata L. Walp.) is widely cultivated throughout the North and Northeastern regions of Brazil. Despite its adaptability to local environmental conditions, some diseases may limit its cultivation. In Septem- ber 2017, cowpea cultivar BR-17 Gurgu eia plants exhibiting root rot, vascular bundle darkening, and wilt symptoms were collected from a field located in Areia county, Para ıba state, Brazil (6 589120 S, 35 429150 W). About 14% of plants in the field were symptomatic. Infected roots and vascular bundle frag- ments from diseased samples were surface sterilized with a sodium hypochlo- rite (1%) solution for 2 min, rinsed multiple times with sterile water, plated on potato dextrose agar (PDA) medium, and incubated at 25 ± 2 C for 7 days. By a single-spore isolation technique, a set of 10 isolates produced floccose and violaceous colonies. Macroconidia were sparse, slightly falcate with three to five septa, and measured 24.9 to 38.3 × 2.1 to 4.2 μm. Ellipti- cal to oval shaped microconidia were produced in short chains from monophialides and polyphialides and measured 4.5 to 9.2 × 1.4 to 3.4 μm. No chlamydospores were observed. These morphological features match those of Fusarium proliferatum (Leslie and Summerell 2006). In order to validate the fungus’s identity, representative isolate FC-01 was prepared for PCR amplification and partial sequencing of the translation elongation factor gene (TEF-1a; GenBank accession no. MW655796). A query of this sequence against the Fusarium-ID database (Geiser et al. 2004) showed 100% similarity (511/511) with F. proliferatum (MN784814.1). Phylogenetic analysis based on maximum likelihood was performed using RAXML-HCP2 v.8.2.12 and grouped the isolate with other F. proliferatum sequences with a high bootstrap value (98%). We also performed a pathogenicity test following the method described by Sousa et al. (2008). In summary, isolate FC-01 was grown on PDA amended with mannitol to adjust the osmotic potential to –1.0 MPa. Cultures were incubated at 25 ± 2 C for 7 days, and then 100 ster- ile cowpea seeds of BR-17 Gurgu eia were placed on them. Seeds distributed over the PDA + mannitol without the fungus were used as a control. After 48 h of exposure, the seeds were sown into 250-ml plastic cups filled with sterile substrate and maintained under greenhouse conditions. Sixteen days after inoculation (DAI) the plants began to show gradual yellowing and wilt- ing symptoms, and a stalk section at 36 DAI revealed darkened vascular bun- dles. In contrast, plants from the control group remained healthy. This test was repeated twice and F. proliferatum was reisolated from the roots and vas- cular bundle of cowpea seedlings, thus confirming Koch’s postulates. Vascu- lar wilt is one of the most important fungal diseases of cowpea (Shrestha et al. 2016). Considering that F. proliferatum is a cosmopolitan fungus that affects a wide host range (Yan 2020), its occurrence on cowpea fields may cause both yield and economic losses for Brazilian farmers. Therefore, pre- cise identification of F. proliferatum is needed to develop effective manage- ment strategies. To the best of our knowledge, this is the first report of F. proliferatum causing vascular wilt in cowpea plants in Brazil.This work was funded by the project “Control of olive anthracnose through gene silencing and gene expression using a plant virus vector” and the project “Development of a new virus-based vector to control TSWV in tomato plants” with the references, co-financed by the European Union through the Euro- pean Regional Development Fund, under the ALENTEJO 2020 (Regional Opera- tional Program of the Alentejo), ALGARVE 2020 (Regional Operational Program of the Algarve) and through the Foundation for Science and Technology, in its national component (ALT20-03-0145-FEDER-028263, PTDC/ASP-PLA/28263/ 2017, ALT20-03-0145-FEDER-028266, and PTDC/ASP-PLA/28266/2017). Plant Dis. 106:1992, 2022; published online as https://doi.org/10.1094/PDIS-04-21- 0839-PDN. Accepted for publication 1 December 2021