Role of ethylene in the protection of tomato plants against soil-borne fungal pathogens conferred by an endophytic Fusarium solani strain

An endophytic fungal isolate (Fs-K), identified as a Fusarium solani strain, was obtained from root tissues of tomato plants grown on a compost which suppressed soil and foliar pathogens. Strain Fs-K was able to colonize root tissues and subsequently protect plants against the root pathogen Fusarium oxysporum f.sp. radicis-lycopersici (FORL), and elicit induced systemic resistance against the tomato foliar pathogen Septoria lycopersici. Interestingly, attenuated expression of certain pathogenesis-related genes, i.e. PR5 and PR7, was detected in tomato roots inoculated with strain Fs-K compared with non-inoculated plants. The expression pattern of PR genes was either not affected or aberrant in leaves. A genetic approach, using mutant tomato plant lines, was used to determine the role of ethylene and jasmonic acid in the plant's response to infection by the soil-borne pathogen F. oxysporum f.sp. radicis-lycopersici (FORL), in the presence or absence of isolate Fs-K. Mutant tomato lines Never ripe (Nr) and epinastic (epi1), both impaired in ethylene-mediated plant responses, inoculated with FORL are not protected by isolate Fs-K, indicating that the ethylene signalling pathway is required for the mode of action used by the endophyte to confer resistance. On the contrary, def1 mutants, affected in jasmonate biosynthesis, show reduced susceptibility to FORL, in the presence Fs-K, which suggests that jasmonic acid is not essential for the mediation of biocontrol activity of isolate Fs-K.     

The use of hydroxyl-radical-generating systems for the treatment of olive mill wastewaters

Three hydroxyl-radical producing biomimetic systems, composed of CuII, hydrogen peroxide and pyridine, glucaric or succinic acid, were able to perform decolorization of olive mill wastewaters (OMW) >85 % within 3 d combined with a significant removal of total phenols (>75 %). The systems consisting of 50 mmol/L succinic acid, 5-10 mmol/L CuSO4 and 100 mmol/L H2O2 were the most effective at OMW treatment, and led to the reduction of phenol contents to <1 % along with high decolorization (>88 %) and acceptable values of chemical oxygen demand.     

<Emphasis Type="Italic">Bacillus</Emphasis> sp. WW3-SN6, a novel facultatively alkaliphilic bacterium isolated from the washwaters of edible olives

A novel Gram-positive facultatively alkaliphilic, sporulating, rod-shaped bacterium, designated as WW3-SN6, has been isolated from the alkaline washwaters derived from the preparation of edible olives. The bacterium is nonmotile, and flagella are not observed. It is oxidase positive and catalase negative. The facultative alkaliphile grows from pH 7.0 to 10.5, with a broad optimum from pH 8.0 to 9.0. It could grow in up to 15% (w/v) NaCl, and over the temperature range from 4° to 37°C, with an optimum between 27° and 32°C: therefore, it is both halotolerant and psychrotolerant. The bacterium is sensitive to a range of β-lactam, sulfonamide, and aminoglycoside antibiotics, but resistant to trimethoprim. The range of amino acids, sugars, and polyols utilized as growth substrates indicates that this alkaliphile is a heterotrophic bacterium. d(+)-glucose, d(+)-glucose-6-phosphate, d(+)-cellobiose, starch, or sucrose are the substrates best utilized. The major membrane lipids are phosphatidylglycerol and diphosphatidylglycerol, with smaller amounts of phosphatidylethanolamine and an unknown phospholipid. During growth at high pH, the proportion of phosphatidylglycerol is increased relative to phosphatidylethanolamine. The fatty acyl components in the membrane phospholipids are mainly branched chain, with 13-methyl tetradecanoic and 12-methyl tetradecanoic acids as the predominant components. The G + C content of the genomic DNA is 41.1 ± 1.0 mol%. The results of 16S ribosomal RNA sequence analysis place this alkaliphilic bacterium in a cluster, together with an unnamed alkaliphilic Bacillus species (98.2% similarity). Received: October 22, 1999 / Accepted: February 27, 2000     

Neofusicoccum parvum and Diaporthe foeniculina associated with twig and shoot blight and branch canker of citrus in Greece

In a survey performed in Chania and Aetoloacarnania, Greece in years 2013–2014, fungal isolates causing twig and shoot blight and branch canker of citrus trees were morphologically characterized and identified by multiple gene sequence analysis. By sequencing the ITS‐5.8S rRNA, the elongation factor 1‐α (EF1‐α), the β‐tubulin and the RNA polymerase II subunit (Rpb2) genes, the isolates examined were associated with Diaporthe foeniculina (six isolates) and Neofusicoccum parvum (one isolate). All six D. foeniculina isolates showed slow colony growth rates (7.4 ± 3.2 mm/day), while the N. parvum isolate exhibited fast growth (41.6 mm/day). Koch's criteria were met after re‐isolation of D. foeniculina isolates from all inoculated Citrus spp. and N. parvum from inoculated C. reticulata “Ortanique” and after having developed symptoms similar to those detected on shoots and branches collected from citrus fields. Based on lesion length on detached C. medica “Lia Kritis” shoots, N. parvum caused long necrotic lesions (58 mm in length) in comparison with a length of 12–21 mm lesions caused by D. foeniculina isolates. Pathogenicity trials on nine Citrus spp., which had been inoculated with D. foeniculina and N. parvum, revealed different levels of susceptibility, indicating a host‐dependent infection effect, with Poncirus trifoliate × C. paradisi (“Citrumelo Swingle”) being the most resistant citrus genotype. Lack of host specificity suggests that their pathogen–host association could be attributed to ecological rather to co‐evolutionary factors. This work represents the first report, accompanied with pathogenicity tests, on botryosphaeriaceous and diaporthaceous pathogens associated with twig and shoot blight and branch canker of citrus in Greece.     

Antagonistic bacteria of composted agro-industrial residues exhibit antibiosis against soil-borne fungal plant pathogens and protection of tomato plants from Fusarium oxysporum f.sp. radicis-lycopersici

Rhizospheric and root-associated/endophytic (RAE) bacteria were isolated from tomato plants grown in three suppressive compost-based plant growth media derived from the olive mill, winery and Agaricus bisporus production agro-industries. Forty-four (35 rhizospheric and 9 RAE) out of 329 bacterial strains showed in vitro antagonistic activity against at least one of the soil-borne fungal pathogens, Fusarium oxysporum f.sp. radicis-lycopersici (FORL), F. oxysporum f.sp. raphani, Phytophthora cinnamomi, P. nicotianae and Rhizoctonia solani. The high percentage of total isolates showing antagonistic properties (13%) and their common chitinase and β-glucanase activities indicate that the cell wall constituents of yeasts and macrofungi that proliferate in these compost media may have become a substrate that favours the establishment of antagonistic bacteria to soil-borne fungal pathogens. The selected bacterial strains were further evaluated for their suppressiveness to tomato crown and root rot disease caused by FORL. A total of six rhizospheric isolates, related to known members of the genera Bacillus, Lysinibacillus, Enterobacter and Serratia and one RAE associated with Alcaligenes faecalis subsp. were selected, showing statistically significant decrease of plant disease incidence. Inhibitory effects of extracellular products of the most effective rhizospheric biocontrol agent, Enterobacter sp. AR1.22, but not of the RAE Alcaligenes sp. AE1.16 were observed on the growth pattern of FORL. Furthermore, application of cell-free culture extracts, produced by Enterobacter sp. AR1.22, to tomato roots led to plant protection against FORL, indicating a mode of biological control action through antibiosis.     

Characterization of cultivated fungi isolated from grape marc wastes through the use of amplified rDNA restriction analysis and sequencing

Microbial assessment of grape marc wastes, the residual solid by-product of the wine-industry, was performed by identifying phylogenetically the fungal culturable diversity in order to evaluate environmental and disposal safety issues and to discuss ecological considerations of applications on agricultural land. Fungal spores in grape marc were estimated to 4.7×10⁶ per g dry weight. Fifty six fungal isolates were classified into eight operational taxonomic units (OTUs) following amplified ribosomal DNA restriction analysis (ARDRA) and colony morphology. Based on 18S rRNA gene and 5.8S rRNA gene-ITS sequencing, the isolates representing OTUs #1, #2, #3, and #4, which comprised 44.6%, 26.8%, 12.5%, and 5.3%, respectively, of the number of the total isolates, were identified as Aspergillus fumigatus, Bionectria ochroleuca, Haematonectria haematococca, and Trichosporon mycotoxinivorans. The isolates of OTU#5 demonstrated high phylogenetic affinity with Penicillium spp., while members of OTUs #6 and #7 were closer linked with Geotrichum candidum var. citri-aurantii and Mycocladus corymbifer, respectively (95.4 and 97.9% similarities in respect to their 5.8S rRNA gene-ITS sequences). The OTU#8 with a single isolate was related with Aspergillus strains. It appears that most of the fungal isolates are associated with the initial raw material. Despite the fact that some of the species identified may potentially act as pathogens, measures such as the avoidance of maintaining large and unprocessed quantities of grape marc wastes in premises without adequate aeration, together with its suitable biological treatment (e.g., composting) prior to any agriculture-related application, could eliminate any pertinent health risks.