Fruit anthracnose caused by Colletotrichum species is a major disease of olive (Olea europaea) worldwide. In this study, we tested in vitro the susceptibility of eight widely grown Italian olive ...cultivars and one Spanish cultivar to five Colletotrichum species. The Italian cultivars were Carolea, Cassanese, Coratina, Dolce Agogia, Frantoio, Leccino, Ottobratica and Sant'Agostino. The Spanish cultivar, included as a reference, was Picual. The five Colletotrichum species, included in pathogenicity tests, were C. acutatum, C. gloeosporioides, C. godetiae, C. karsti and C. nymphaeae. Olive drupes at comparable ripening stage were wound‐inoculated with a conidial suspension and the severity of infections was rated at various time intervals after inoculation using a scale of 0 to 6. The results were expressed in terms of relative area under disease progress curve (rAUDPC). C. acutatum was the most aggressive while C. karsti was the least aggressive among the Colletotrichum species tested. Frantoio and Leccino were the least susceptible cultivars while Ottobratica, Coratina and Carolea were the most susceptible to all Colletotrichum species. Separate experiments aimed to evaluate the effect of both inoculation method and drupe ripening stage on the interaction between Colletotrichum species and olive cultivars. Only C. acutatum and C. nymphaeae induced symptoms in nonwounded drupes. In general, the disease severity in green drupes was significantly lower than in mature drupes; however, the rankings of olive cultivars for their susceptibility to Colletotrichum species on both green and mature drupes showed similar trends.
Pathogenicity tests show a great variability in both the virulence of diverse Colletotrichum species associated with olive anthracnose and susceptibility of olive cultivars to infection by these species.
The fungal diversity associated with leaves, flowers and fruits of olive (Olea europaea) was investigated in different phenological stages (May, June, October and December) using an implemented ...metabarcoding approach. It consisted of the 454 pyrosequencing of the fungal ITS2 region and the subsequent phylogenetic analysis of relevant genera along with validated reference sequences. Most sequences were identified up to the species level or were associated with a restricted number of related taxa enabling supported speculations regarding their biological role. Analyses revealed a rich fungal community with 195 different OTUs. Ascomycota was the dominating phyla representing 93.6% of the total number of detected sequences followed by unidentified fungi (3.6%) and Basidiomycota (2.8%). A higher level of diversity was revealed for leaves compared to flowers and fruits. Among plant pathogens the genus Colletotrichum represented by three species (C. godetiae syn. C. clavatum, C. acutatum s.s and C. karstii) was the most abundant on ripe fruits but it was also detected in other organs. Pseudocercospora cladosporioides was detected with a high frequency in all leaf samples and to a less extent in ripe fruits. A much lower relative frequency was revealed for Spilocaea oleagina and for other putative pathogens including Fusarium spp., Neofusicoccum spp., and Alternaria spp. Among non-pathogen taxa, Aureobasidium pullulans, the species complex of Cladosporium cladosporioides and Devriesia spp. were the most represented. This study highlights the existence of a complex fungal consortium including both phytopathogenic and potentially antagonistic microorganisms that can have a significant impact on olive productions.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
spp. are known as biocontrol agents of fungal plant pathogens and have been recognized as a potential source of bioactive metabolites. The production of antimicrobial substances from strains
.
(TS) ...and
.
(IMI 393899) was investigated. The bioactivity of 10- and 30-day culture filtrate extracted with ethyl acetate was assessed against a set of pathogenic fungi and oomycetes. The 30-day extracts of both strains had significant cytotoxic effects against the tested pathogens, with values of minimum fungicidal concentration (MFC) ranging between 0.19 and 6.25 mg/mL. Dual culture assay (direct contact and nondirect contact) and the percentage inhibition of radial growth (PIRG) was calculated. The highest PIRG values were 76% and 81% (direct contact) with IMI 393899 and TS, respectively. Nondirect contact does not show inhibition on any of pathogens tested, indicating that the inhibition is not due to the secretion of volatile substances. Culture filtrates were analyzed by GC-MS and HPLC-Q-TOF-MS for the identification of volatile organic compounds (VOCs) and nonvolatile organic compounds (nVOCs), respectively. Seven classes of VOCs and 12 molecules of nVOCs were identified. These results indicate that these strains of
had antimicrobial activities and they are potential natural sources of compounds with biological activity.
Decoding the mechanisms of plant defense against plant pathogens in a scenario where antagonistic activity and the plant growth-promoting effects of useful organisms intervene simultaneously is a new ...frontier of plant pathology. Here, we demonstrated that (i) two selected strains of
Trichoderma asperellum
and
Trichoderma atroviride
promoted tomato (
Solanum lycopersicum
) growth and reduced the severity of disease caused by the oomycete
Phytophthora nicotianae
and (ii) the genetic patterns of the components of the experimental model system tomato–
Trichoderma
spp.–
P. nicotianae
were differentially expressed. The beneficial effects in both the promotion of the growth of host plant and the biological control of the pathogen by two selected strains of different
Trichoderma
species were tested both
in planta
and
in vitro
. In both respects,
T. atroviride
demonstrated to be more effective than
T. asperellum
. Additionally, the simultaneous transcriptional reprogramming of several plant defense-related genes, pathogen effectors, and mycoparasitism-related genes in tomato,
P. nicotianae
, and
Trichoderma
spp., respectively, was evaluated during the three-component interaction. Results support the hypothesis that
Trichoderma
spp. elicit the expression of plant defense-related genes. As expected, a mycoparasitism-related gene was significantly up-regulated in
Trichoderma
-colonizing tomato plants infected by
P. nicotianae
. Finally, a marked up-regulation of the genes encoding two necrosis-inducing effectors was observed in
P. nicotianae
infecting tomato plants colonized by
Trichoderma
. In conclusion, this study is a contribution toward understanding the genetic pathways related with the ability of
Trichoderma
spp. to counteract the challenge of
P. nicotianae
infections on tomato. Additionally, the experiments revealed the beneficial effects in the tomato growth promotion of a new
T. atroviride
strain and its good antagonistic effectiveness in the biological control of root and crown rot incited by
P. nicotianae
, confirming that
Trichoderma
spp. can be a powerful tool in integrated pest management strategies of
Phytophthora
diseases of horticultural crops.
An amplicon metagenomic approach based on the ITS2 region of fungal rDNA was used to identify the composition of fungal communities associated with different strawberry organs (leaves, flowers, ...immature and mature fruits), grown on a farm using management practices that entailed the routine use of various chemical pesticides. ITS2 sequences clustered into 316 OTUs and Ascomycota was the dominant phyla (95.6%) followed by Basidiomycota (3.9%). Strawberry plants supported a high diversity of microbial organisms, but two genera, Botrytis and Cladosporium, were the most abundant, representing 70-99% of the relative abundance (RA) of all detected sequences. According to alpha and beta diversity analyses, strawberry organs displayed significantly different fungal communities with leaves having the most diverse fungal community, followed by flowers, and fruit. The interruption of chemical treatments for one month resulted in a significant modification in the structure of the fungal community of leaves and flowers while immature and mature fruit were not significantly affected. Several plant pathogens of other plant species, that would not be intuitively expected to be present on strawberry plants such as Erysiphe, were detected, while some common strawberry pathogens, such as Rhizoctonia, were less evident or absent.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This study was aimed at testing the integrated use of a natural biostimulant based on seaweed (
) and plant (alfalfa and sugarcane) extracts and reduced dosages of the conventional synthetic ...fungicide Imazalil (IMZ) to manage postharvest rots of orange fruits. The following aspects were investigated: (i) the effectiveness of postharvest treatment with natural biostimulant alone or in mixture with IMZ at a reduced dose against green mold caused by
; (ii) the differential expression of defense genes in orange fruits treated with the natural biostimulant both alone and in combination with a reduced dose of IMZ; (iii) the persistence of the inhibitory activity of both biostimulant and the mixture biostimulant/IMZ against green mold; and (iv) the residue level of fungicide in citrus peel when applied alone or in combination with the biostimulant. Treatments with the chemical plant resistance-inducer potassium phosphite, alone or with a reduced dose of IMZ, were included for comparison. The mixture of natural biostimulant and IMZ at a low dose consistently reduced the incidence and severity of fruit green mold and induced a significant increase of the expression level of β-1,3-glucanase-, peroxidase (PEROX)-, and phenylalanine ammonia-lyase (PAL)-encoding genes in fruit peel, suggesting that the natural biostimulant elicits a long-lasting resistance of citrus fruits to infections by
. Interestingly, the residual concentration of IMZ in fruits treated with the biostimulant/fungicide mixture was significantly lower than that of IMZ in fruits treated only with the fungicide at the same dose and by far below the threshold values set by the European Union. This study laid the foundations for (i) conceiving a practical and more eco-friendly alternative to the conventional postharvest management of green mold of citrus fruits, based almost exclusively on the use of synthetic fungicide IMZ, alone or mixed with potassium phosphite and (ii) providing a better insight into the mechanisms of disease resistance induction by biostimulants.
•Antifungal activity of Arthrospira platensis and Lactiplantibacillus plantarum.•Enhanced antifungal activity of fermented lactobacilli/cyanobacterium consortia.•Fermentates of consortia inhibit ...growth of toxigenic fungi on agricultural produces.•UHPLC-Q-TOF-MS analysis of metabolites in fermentates of microbial consortia.•Cell-free supernatants of fermented microbial consortia as promising BCA candidates.
The objectives of this study were to (i) test the in vitro inhibitory activity of fermented consortia of the cyanobacterium Arthrospira platensis (syn. Spirulina platensis) and two selected strains of the Lactiplantibacillus plantarum (formerly Lactobacillus plantarum) against a set of toxigenic fungal plant pathogens, including Alternaria alternata, Aspergillus niger, A. flavus, Fusarium graminearum, Giberella zeae, Penicillium commune, and P. expansum, (ii) assess the efficacy of consortia fermentates in preventing infections of F. graminearum and P. expansum on maize cobs and lemon fruits, respectively, and (iii) identify and quantify antifungal compounds and secondary metabolites produced by these consortia. A noticeably inhibitory activity of the fermented consortia, as determined by the agar diffusion test, was observed for all the fungal pathogens tested. Fusarium graminearum and G. zeae were the most sensitive, while A. flavus and A. niger were the least sensitive. Cell-free supernatants (CFSs) of fermentates showed the highest antifungal activity after 24 and 48 h of incubation. Their MIC and MFC values ranged from 3.13 (G. zeae) to 25 g L−1 (A. niger) and from 3.13 (G. zeae) to 100 g L−1 (Aspergillus and Penicillium species), respectively. CFSs of fermentates were also effective in preventing infections by two very common toxigenic fungi, F. graminearum and P. expansum, in maize cobs and lemon fruits, respectively. Results of chemical analyses suggest the antifungal activity of fermentates depend, at least in part, on the presence of high levels of lactic acid and significantly higher concentrations of some phenolic compounds, including DL-3-phenallactic acid, benzoic acid and 3–4-dihydroxy hydrocinnamic acid. Among the 66 secondary metabolites detected in fermentates by UHPLC-Q-TOF-MS analysis, only benzoic acid, leucine, oleic acid, and proline possess antifungal activity. Overall, results of this study reveal the potential of fermented microbial consortia as BCAs to prevent post-harvest fungal diseases and contamination by mycotoxins of food and agricultural produces.
An investigation into oomycete diversity in rice paddies of Fars Province in Iran led to the identification of two new Pythium sensu lato (s.l.) species as Globisporangium izadpanahii sp. nov. and ...Pythium banihashemianum sp. nov. The identification was based on morphological and physiological features as well as on the phylogenetic analysis of nuclear (ITS and βtub) and mitochondrial (cox1 and cox2) loci using Bayesian inference and Maximum Likelihood. The present paper formally describes these two new species and defines their phylogenetic relationships with other congeneric species. According to multiple gene genealogy analysis, G. izadpanahii sp. nov. was grouped with other species of Globisporangium (formerly, clade G of Pythium s.l.) and was closely related to both G. nagaii and the recently described G. coniferarum. The second species, designated P. banihashemianum sp. nov., was grouped with other species of Pythium sensu stricto (formerly, clade B of Pythium s.l.) and, according to the phylogenetic analysis, shared an ancestor with P. plurisporium. The production of globose hyphal swellings was a major characteristic of G. izadpanahii sp. nov., which did not produce vesicles and zoospores. In pathogenicity tests on rice seedlings, P. banihashemianum sp. nov. isolates were highly pathogenic and caused severe root and crown rot, while G. izadpanahii sp. nov. isolates were not pathogenic.
is responsible for brown or chalky nut rot in sweet chestnut (
), causing heavy reductions in nut production. Controlling it is challenging, due to its inconspicuous infections, erratic colonization ...of host tissues and endophytic lifestyle. Fungicides are not applicable because they are prohibited in chestnut forests and strongly discouraged in fruit chestnut groves.
species are safe and wide-spectrum biocontrol agents (BCAs), with a variety of beneficial effects in plant protection. This study tested selected strains of
,
and
for their ability to suppress
. Field experiments were conducted in four chestnut groves (two test plots plus two controls) at two sites with a different microclimate. As the size of the trees were a major drawback for uniform and effective treatments, the
strains were delivered directly by trunk injection, using the BITE
(Blade for Infusion in TrEes) endotherapic tool. The BCA application, repeated twice in two subsequent years, significantly reduced nut rot incidence, with a more marked, presumably cumulative, effect in the second year. Our data showed the tested
strains retain great potential for the biological control of
in chestnut groves. The exploitation of
spp. as biopesticides is a novelty in the forestry sector and proves the benefits of these microbes in plant disease protection.
The aim of this study was to determine the effectiveness of a Super absorbent polymer (SAP) containing copper (SAP-Cu) in controlling mal secco disease (MSD) of lemon caused by the fungus
Plenodomus ...tracheiphilus
. Super absorbent polymer containing copper was characterized by atomic absorption spectrometry (AAS) and UV-VIS spectroscopy.
In vitro
tests were performed to determine the inhibitory effects of SAP-Cu against the pathogen on both potato-dextrose-agar medium and naturally infected lemon cuttings. Super absorbent polymer was able to absorb up to about 200 and 30 times its weight of ionized water and copper (II) sulfate solution (Cu
2+
ions at the concentration 236 mM), respectively. The distribution of copper released on twigs after 24 h of contact with SAP-Cu was determined by secondary ion mass spectrometry with time-of-flight analyzer (ToF-SIMS). Super absorbent polymer containing copper significantly inhibited the viability of
P. tracheiphilus
in lemon twigs. Overall, the results of this study showed that the SAP could be a suitable carrier of antifungal compounds.
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