ABSTRACT
Plasma-liquid interaction research has developed substantially in recent years due, mostly, to the numerous applications of cold atmospheric plasma (CAP). Plasma-liquid interactions are influenced by the concentrations of the ionic species present in the liquid environment, and few studies have paid attention to saline water, which generally mediates the reactions in many plasma applications. Therefore, the present review aims to explore the main results and the influence of variables on the modification of properties of saline water by CAP sources following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The searches were carried out in the Scopus, Science Direct, and Web of Science databases, resulting in the inclusion of 37 studies. The main effects of the interaction between CAP and saline water are (i) the production of reactive oxygen and nitrogen species (RONS); (ii) the increase in conductivity and decrease in pH, directly proportional to the increase in discharge voltage; (iii) and the effective area of interaction and the shortest distance between electrode and solution. Other effects are the localized evaporation and crystallization of salts, which make the interaction between plasma and saline water a promising field in the development of technologies for desalination and improvement of liquid properties.
ABSTRACT
Watermelon (Citrullus lanatus (Thumb.) Matsum. & Nakai) is an important crop in Brazil both for export and domestic consumption. In October 2019, watermelon plants showing decline and root rot symptoms were surveyed in 16 commercial fields in Baraúna's municipality (Rio Grande do Norte, Brazil). The disease prevalence was 12.5%, and the average incidence was 5%. Affected root segments were cut into small pieces and surface-disinfected with 70% ethyl alcohol and 1.5 % NaOCl for 1 and 2 min, respectively. Tissues were plated onto potato dextrose agar (PDA) and incubated at 25°C for 7 days. Fungal colonies developed from the infected tissues were dark or greyish, and pure cultures were obtained by hyphal tip isolation technique. Six fungal isolates with the same morphology were obtained. Two of them were selected for morphological and molecular characterization (CFC-1123 and CFC-1124). Isolates grew rapidly in PDA, covering the entire surface of the Petri dishes within 3 days. The aerial mycelium was initially white, turning dark greenish-gray after 4 to 5 days of incubation at 25°C in the dark. Isolates produced pycnidia and conidia in water-agar medium with sterilized pine needles after 30 days of incubation at 25°C under near-UV light. The conidia were initially hyaline and brown with central transverse septum and longitudinal streaks when mature. Conidia were ellipsoid to oval (22.83 ± 3.1 µm long and 11.58 ± 1.5 µm wide). Based on morphological features, the isolates were initially identified as Lasiodiplodia sp. (Phillips et al. 2013). To confirm the identification, genomic DNA was extracted and the internal transcribed spacer (ITS) region as well as fragments of the translation elongation factor 1-α (TEF) and ß-tubulin 2 (TUB) genes were amplified using the primer pairs ITS1/ITS4 (White et al. 1990), EF1-728F/EF1-986R (Carbone and Kohn 1999) and Bt2a/Bt2b (Glass and Donaldson 1995), respectively. The sequences were deposited in GenBank under accession numbers OL841380, OL865376 and OL890691 for CFC-1123, and OL841381, OL865377 and OL890692 for CFC-1124. Maximum likelihood phylogenetic analysis of the concatenated sequences of ITS, TEF and TUB gene regions of some reference sequences and ex-types of Lasiodiplodia spp. was performed. Phylogenetic analysis revealed that the isolates grouped in the L. brasiliensis clade (Netto et al. 2014) with 80/79% of bootstrap. The isolates were deposited in the Culture Collection of Phytopathogenic Fungi from Cariri (CFC) at the Universidade Federal do Cariri (Crato, Brazil). Pathogenicity of the two isolates was determined using colonized wheat grains as inoculum source. One watermelon seed (cv. Crimson Sweet) was placed in a sterile plastic pot (500-mL) filled with 6 cm layer of a substrate composed of soil and Tropstrato® (5:1 w/w). Three wheat grains (50 mg) colonized with each isolate were placed 10 mm above the seed and covered with the substrate. Control pots were inoculated only with sterile wheat grains. There were five replicates for each isolate. The pots with seedlings were maintained in a greenhouse at 28 ± 2°C under natural light conditions. The inoculated seedlings showed poor growth, withering and drying leaves 45 days after inoculation (DAI), and subsequently root rot symptoms and death at 60 DAI. Control seedlings remained asymptomatic. The pathogen was re-isolated from all inoculated seedlings and identified by conidia morphology to fulfill Koch's postulates. Lasiodiplodia brasiliensis has been reported to cause postharvest rot and gummosis of watermelon (Farr and Rossman 2022). However, to our knowledge, this is the first report of watermelon decline caused by this fungus in Brazil and worldwide. This finding must be considered for developing efficient control strategies for the disease.
ABSTRACT
Citrus canker caused by Xanthomonas citri subsp. citri is one of the most important citrus diseases in the world (Gottwald et al. 2002), mainly for citrus-producing countries with humid sub-tropical regions such as United States, Argentina, and Brazil, where losses may be significant (Behlau et al. 2020). In the state of Rio Grande do Norte (RN), Brazil, citrus production is expanding and shows social and economic importance for small farmers, which produced approximately 297 tons of lime in this state in 2019 (IBGE 2021). In December 2019, we observed symptoms of erumpent lesions with margins surrounded by yellow haloes on leaves and fruit of the lime (Citrus aurantifolia cv. 'Galego') (about 5% incidence) in a plantation located in the municipality of Mossoró, RN (05°12'21.1"S, 37°19'16"W). Samples were collected from the lime orchard, and five bacterial strains (CCRMXC01 to CCRMXC05) showing yellow, convex, mucoid colonies were isolated in a nutrient-yeast-dextrose-agar medium (NYDA). Pathogenicity tests were performed on sweet orange (C. sinensis cv. 'Pêra') and lime (C. latifolia cv. 'Tahiti') seedlings. Four wounds per leaf (upper side) were carried out with an entomological pin and 10 µl of a bacterial suspension (108 CFU mL-1) were deposited on each wound. The negative control consisted of leaves treated with sterile distilled water (SDW). For each citrus species, we used four replicates per strain and one leaf with four wounds per replicate. Inoculated leaves developed erumpent lesions with margins surrounded by yellow haloes six days after inoculation (DAI) in both citrus species, while leaves treated with SDW remained symptomless. Nine DAI, we reisolated the pathogen and performed rep-PCR (REP, ERIC, and BOX-PCR) analyses (Gama et al. 2018) with the strains inoculated and reisolated to confirm the identity of the strains and to fulfill Koch's postulates. The strains were stored at the Culture Collection Rosa Mariano (CCRM) of the Phytobacteriology Laboratory at the Universidade Federal Rural de Pernambuco. The five strains reisolated showed the same REP, ERIC, and BOX-PCR profiles as the strains used for inoculations. The molecular identification was performed sequencing the dnaK, fyuA, gyrB, and rpoD genes (Young et al. 2008). Each fragment was sequenced in both the forward and reverse directions. Using the BLASTn tool, we observed that sequences of the dnaK (GenBank MW218913 to MW218917), fyuA (GenBank MW218918 to MW218922), and rpoD (GenBank MW218928 to MW218932) genes of the strains CCRMXC01 to CCRMXC05 showed 100% of identity with the sequences of these genes from the type strain (ICMP 24T) and of other strains of X. citri subsp. citri (ICMP 21 and ICMP 7493), while sequences of gryB (GenBank MW218923 to MW218927) of the former strains showed 100% identity with the gyrB sequence of the strains ICMP 24T and ICMP 7493 and 99,85% identity with strain ICMP 21. This short variation in the sequence of the gyrB gene also may be observed among strains of X. citri subsp. citri available in NCBI database (https://www.ncbi.nlm.nih.gov/). The phylogenetic analysis performed using Bayesian inference and the concatenated sequence of all the type or representative strains of species and pathovars of Xanthomonas available in GenBank showed that the strains CCRMXC01 to CCRMXC05 clustered together with strain ICMP 24T with 1.0 posterior probability. To our information, this is the first report of X. citri subsp. citri causing citrus canker on lime in RN state, Brazil.
ABSTRACT
In this study, five new recently described Monosporascus species, M. brasiliensis, M. caatinguensis, M. mossoroensis, M. nordestinus, and M. semiaridus, which were found on weeds collected from cucurbit cultivation fields in northeastern Brazil, are characterized regarding mycelial growth at different pH levels and salinity (NaCl) concentrations, their pathogenicity to selected cucurbit species, and their sensitivity to fungicides with different modes of action. Our results reveal great variability among the representative isolates of each Monosporascus spp. All of them showed a wide range of tolerance to different pH levels, and NaCl significantly reduced their in vitro mycelial growth, although no concentration was able to inhibit them completely. In pathogenicity tests, all seedlings of cucurbits evaluated, melon, watermelon, cucumber, and pumpkin, were susceptible to the five Monosporascus spp. in greenhouse experiments using artificial inoculation of roots. Moreover, all Monosporascus spp. were highly susceptible to the fungicides fludioxonil and fluazinam. Our findings provide relevant information about the response of these new Monosporascus spp. to environmental factors, plant genotypes and fungicides.
