Biology subjects

Riolo, M.

Publications and source records attributed to Riolo, M..

6 recordsLinked to original sources

bioRxiv2024

Exploring the Impact of Various Treatments on Gene Expression in Olive (Olea europaea L.) Drupes Affected by Phytophthora oleae: Insights from RNA sequencing-based transcriptome analysis.

Phytophthora oleae is a pathogen recently reported to cause fruit rot on olive orchards in Italy and root rot in a natural wild-olive forest in Spain. RNAseq analysis was conducted to gain insight into the molecular mechanisms that trigger a plant defense response upon the inoculation of drupes with P. oleae and the pre- treatment with the antagonistic yeast Candida oleophila or with culture filtrates of the antagonistic filamentous fungus Trichoderma atroviride. Both treatments were applied to the olive drupe 24 h before the inoculation with the pathogen. Although no full resistance was observed, the virulence of P. oleae was reduced when the drupes were co-inoculated with the yeast or treated with culture filtrates of Trichoderma. Severity of Phytophthora rots in olive drupes was assessed at 24, 72, and 168 hours post pathogen inoculation (hpi) and rated based on an empirical scale. The most effective in reducing the disease severity of P. oleae infection on olive fruit was the treatment with T. atroviride filtrate (56% reduction), followed by C. oleophila (52%). Results showed that 2,466, 1,883, and 1,757 genes were differentially expressed in response to P. oleae, to the binary pathosystem C. oleophila and P. oleae, and T. atroviride and P. oleae, respectively, as compared to wound. Differential RNAseq by DESeq2, performed at 72 hours post-inoculation, and qPCR validation, at 24, 72, and 168 hpi, of the top differentially expressed genes defined a new pattern of plant defense mechanisms involving both PAMP and ETI immunity, with production of ROS and PRs.

plant biology↗

bioRxiv2024

Biological Control of Green Mold in Simulated Post-harvest Chain of Citrus Fruit: Efficacy of Candida oleophila Strain O and Molecular Insight into Elicitation of Host Immune System

Managing post-harvest decays in citrus fruit without relying on conventional pesticides presents a significant challenge in modern Plant Pathology. This study aimed to evaluate the efficacy of the biological control agent Candida oleophila strain O in controlling green mold caused by Penicillium digitatum throughout various stages of the post-harvest supply chain. Using a series of in vivo experiments, different scenarios of P. digitatum infections in clementine tangerine, orange, and lemon fruit were examined, with treatments applied before, during or after infection. The study simulated typical conditions of the citrus supply chain, including picking, processing in packinghouses, and transportation, as well as cold storage and shelf-life phases. Results indicated that C. oleophila exhibited significant efficacy in reducing green mold symptoms, even at shelf-life temperatures, making it a practical alternative to conventional fungicides. Additionally, the study provided insights into the molecular mechanisms underlying the defensive response of citrus fruit to C. oleophila treatment, with up-regulation of defense-related genes observed across different fruit types. Overall, this study underscores the potential of C. oleophila as a sustainable and effective solution for managing post-harvest decays in citrus fruit within the complexities of the supply chain.

plant biology↗

bioRxiv2023

Diversity of mycotoxins and other secondary metabolites re-covered from blood oranges infected by Colletotrichum, Alternaria, and Penicillium species.

This study identified secondary metabolites produced by Alternaria alternata, Colletotrichum gloeosporioides and Penicillium digitatum in fruits of two blood orange cultivars before harvest. Analysis was performed by UHPLC-Q-TOF-MS. Three types of fruits were selected, asymptomatic, symptomatic showing necrotic lesions caused by hail, and mummified. Extracts from peel and juice were analyzed separately. Penicillium digitatum was the prevalent species recovered from mummified and hail-injured fruits. Among 47 secondary metabolites identified, 16, 18 and 13 were of A. alternata, C. gloeosporioides and P. digitatum, respectively. Consistently with isolations, indicating the presence of these fungi also in asymptomatic fruits, the metabolic profiles of the peel of hail-injured and asymptomatic fruits did not differ substantially. Major differences were found in the profiles of juice from hail injured and mummified fruits, such as a significant higher presence of 5,4-dihydroxy-3,7,8-trimethoxy-6C-methylflavone and Atrovenetins, particularly in the juice of mummified fruits of Tarocco Lempso cultivar. Moreover, the mycotoxins Patulin and Rubratoxin B were detected exclusively in mummified fruits. Patulin was detected in both the juice and peel, with a higher relative abundance in the juice, while Rubratoxin B was detected only in the juice. These findings provide basic information for evaluating and preventing the risk of contamination by mycotoxins in the citrus fresh fruit supply chain and juice industry.

plant biology↗

bioRxiv2022

Secondary metabolites produced by Colletotrichum spp. on different olive cultivars

This study was aimed to characterize the secondary metabolites produced by four Colletotrichum species, C. acutatum, C. gloeosporioides, C. godetiae and C. karsti, both in vitro, on potato dextrose agar (PDA) and oatmeal agar (OA), and during the infection process of fruits of four olive cultivars differing in susceptibility to anthracnose, Coratina and Ottobratica, both susceptible, Frantoio and Leccino, both resistant. The metabolites were extracted from axenic cultures after seven days incubation and from olives at three different times, 1, 3 and 7 days post inoculation (dpi). They were identified using the HPLC-QTOF analysis method. In total, as many as 45 diverse metabolites were identified; of these 29 were detected on infected olives and 26 in axenic cultures on agar media (OA and PDA). Only 10 metabolites were present in both fruits and axenic cultures while 19 were found exclusively on olives and 16 exclusively in axenic cultures. The 45 identified metabolites comprised fatty acid, phenolics, pyrones, sterols, terpenes and miscellaneous compounds. Each Colletotrichum species produced a different spectrum of metabolites depending of the type of matrices. On artificially inoculated olives the severity of symptoms, the amount of fungal secondary metabolites and their number peaked 7 dpi irrespective of the cultivar susceptibility and the virulence of the Colletotrichum species. The metabolite profiles as represented by heat maps were the result of the interaction olive cultivar x Colletotrichum species.

plant biology↗

bioRxiv2022

Antifungal activity of selected lactic acid bacteria from olive drupes

In this study, 16 Lactobacilli (LABs) isolated from the drupes of olive (Olea europaea) oil varieties were identified as Lactiplantibacillus plantarum (seven isolates), Pediococcus pentosaceus (six isolates), Enterococcus faecium (two isolates) and Streptococcus salivarius (a single isolate) by peptide mass fingerprinting and sequencing of the 16S rRNA. Antifungal activity of LABs and their cell-free fermentates (CFSs) against several plant pathogenic fungi and oomycetes (fungi sensu lato), including Alternaria, Aspergillus Colletotrichum, Penicillium, Plenodomus and Phytophthora, was evaluated in vitro using the culture overlaying and the agar diffusion tests. Minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) were determined. LABs showed antifungal activity against the fungi sensu lato tested. The most noticeable inhibitory activity was shown by isolates of L. plantarum and P. pentosaceus against Fusarium oxysporum, Colletotrichum species and Penicillium nordicum. Chemical analysis revealed CFSs contained acid lactic and variable quantities of 14 diverse phenolic acids and 26 volatile organic compounds (VOCs). No obvious correlation was found between the metabolic profile of LABs and their antifungal efficacy. However, it is the first time that the potential of fermentates of LABs, recovered from drupes of olive oil varieties, as natural fungicides, was demonstrated.

microbiology↗

bioRxiv2018

Competition and immigration lead to clusters of similar species, not trait separation

Patterns of trait distribution among competing species can potentially reveal the processes that allow them to coexist. It has been recently proposed that competition may drive the spontaneous emergence of niches comprising clusters of similar species, in contrast with the dominant paradigm of greater-than-chance species differences. However, current clustering theory relies largely on heuristic rather than mechanistic models. Furthermore, studies of models incorporating demographic stochasticity and immigration, two key players in community assembly, did not observe clusters. Here we demonstrate clustering under partitioning of resources, partitioning of environmental gradients, and a competition-colonization tradeoff. We show that clusters are robust to demographic stochasticity, and can persist under immigration. While immigration may sustain clusters that are otherwise transient, too much dilutes the pattern. In order to detect and quantify clusters in nature, we introduce and validate metrics which have no free parameters nor require arbitrary trait binning, and weigh species by their abundances rather than relying on a presence-absence count. By generalizing beyond the circumstances where clusters have been observed, our study contributes to establishing them as an update to classical trait patterning theory.\n\nAuthor SummarySpecies traits determine how they compete with each other. As such, patterns in the distributions of traits in a community of competing species may reveal the processes responsible for coexistence. One central idea in theoretical ecology is that the strength of competition relates to similarity in species needs and strategies, and therefore if competition plays out at short timescales, coexisting species should be more different than expected by chance. However, recent theory suggests that competition may lead species to temporarily self-organize into groups with similar traits. Here we show that this clustering is a generic feature of competitive dynamics, which is robust to demographic stochasticity and can be indefinitely maintained by immigration. We show that clustering arises whether species coexist by partitioning resources, environmental preferences, or through tradeoffs in life-history strategies. We introduce and validate metrics that, given species traits and abundances, determine whether they are clustered, and if so, how many clusters occur. By showing the generality of self-organized species clusters and providing a tools for their detection, our study contributes to updating classical ideas about how competition shapes communities, and motivates searches for them in nature.

ecology↗