Olive Fungal Epiphytic Communities Are Affected by Their Maturation Stage

Abstract

The phyllosphere comprises the aerial parts of plants and is colonized by a great diversity of microorganisms, either growing inside (as endophytes) or on the surface (as epiphytes) of plant tissues. The factors that structure the diversity of epiphytes and the importance of these microorganisms for host plant protection have been less studied when compared to the case of endophytes. In this work, the epiphytic fungal communities from fruits of the olive tree (olives) in different maturation stages (green and semi-ripened), obtained from different olive orchard managements (integrated and organic production) and from distinct cultivars displaying different susceptibilities to olive anthracnose (Cobrançosa and Madural), are compared by using a metabarcoding approach. We discuss whether such differences in host resistance against anthracnose depend on both the fungal taxa or fungal community composition. A total of 1,565 amplicon sequence variants (ASVs) were obtained, mainly belonging to the Ascomycota phylum and Saccharomycetes class. Although significant differences on epiphytic fungal richness were observed among olives obtained in different production systems and maturation stages, these factors in addition to host cultivar did not influence the composition of the epiphytes. Despite these results, a co-inertia analysis showed that Aureobasidium spp. and Sporocadaceae spp. were positively associated with the green olives of the cv. Madural produced under integrated production, while Saccharomycetales spp. (Kluyveromyces, Candida, Kazachstania and Saccharomyces) were positively associated with the semi-ripened olives of the cv. Cobrançosa obtained from organic production. The discriminant power of these fungi, some of them recognized as biocontrol agents, suggest that they might be important in conferring differences on host plant susceptibility to anthracnose.

Leaf-Associated Epiphytic Fungi of Gingko biloba, Pinus bungeana and Sabina chinensis Exhibit Delicate Seasonal Variations

“…The leaf-associated fungal abundance of Ginkgo biloba was significantly higher in May than in October, which may be related to the different maturation of leaves. Studies have shown that significant differences in epiphytic fungal richness were observed among olives obtained in different production systems and maturation stages [ 55 ]; whereas, in the same production system, there was no statistical significance in richness regarding olive cultivars, and this result is consistent with the reports of epiphytic fungal communities in olives [ 56 ] and mango fruits [ 57 ] from different cultivars studied using culture-dependent methods. The screening role of host plant species on the epiphytic fungal communities [ 38 , 43 ] has been fully confirmed and attributed to different ecological strategies as well as the chemical and functional properties of host plants.…”

Confronting stresses affecting olive cultivation from the holobiont perspective

“…Recently, the epiphytic fungal communities present in olive cultivars displaying different tolerance to anthracnose have been described as well (Castro et al, 2022) (Table 3). In this study neither the cropping system nor the plant genotype significantly influenced the composition of the fungal community, while the fruit maturation stage produced a strong impact on the epiphytic mycobiome.…”

Nanopore-Sequencing Metabarcoding for Identification of Phytopathogenic and Endophytic Fungi in Olive (Olea europaea) Twigs

“…Olive (Olea europaea L.) is a main crop cultivated within the Mediterranean region due to its local and historically high socioeconomic importance. It is putatively expanding cultivation on a global scale due to the growing awareness in olive oil's consumption's health benefits, and, furthermore, as a rich source (including drupes, olive oil, and olive drupe processing byproducts) of biologically active compounds valuable for food, cosmetic, and pharmaceutical industries [25][26][27]. Though moderately tolerant to abiotic stress such as drought and salinity [28], the olive tree is host for many pests and a variety of pathogenic microorganisms, mainly fungi, resulting in a multitude of diseases and consequent decrease in tree fitness, productivity, and oil quality [29].…”

“…Currently, several metagenomics studies regarding the epiphytic and endophytic mycoflora of olive phyllosphere and carposphere are available. These span the analysis of fungal diversity under different phenological stages [53], composition of microbial epiphytical communities on olive drupe in relation to maturation process and genotype [25], phyllosphere endophytic mycobiome of different cultivars [26], and host-pathogen interactions in association with the phyllosphere mycobiome [27,54]. Similar approaches regarding spoilage microorganisms during fermentation [55], effect of salt stress on leaf endophytic bacterial communities of different cultivars [56], or the genotype effect on bacterial populations [57], provide data on the shapes of phyllosphere or carposphere bacterial communities.…”