Bacterial disease induced changes in fungal communities of olive tree twigs depend on host genotype

Abstract

In nature, pathogens live and interact with other microorganisms on plant tissues. Yet, the research area exploring interactions between bacteria-fungi and microbiota-plants, within the context of a pathobiome, is still scarce. In this study, the impact of olive knot (OK) disease caused by the bacteria Pseudomonas savastanoi pv. savastanoi (Psv) on the epiphytic and endophytic fungal communities of olive tree twigs from three different cultivars, was investigated in field conditions. The ITS-DNA sequencing of cultivable fungi, showed that OK disease disturbs the resident fungal communities, which may reflect changes in the habitat caused by Psv. In particular, a reduction on epiphyte abundance and diversity, and changes on their composition were observed. Compared to epiphytes, endophytes were less sensitive to OK, but their abundance, in particular of potential pathogens, was increased in plants with OK disease. Host genotype, at cultivar level, contributed to plant fungal assembly particularly upon disease establishment. Therefore, besides fungi - Psv interactions, the combination of cultivar - Psv also appeared to be critical for the composition of fungal communities in olive knots. Specific fungal OTUs were associated to the presence and absence of disease, and their role in the promotion or suppression of OK disease should be studied in the future.

Impact of plant genotype and plant habitat in shaping bacterial pathobiome: a comparative study in olive tree

“…Although there are still gaps in understanding the dynamism and complexity of such metabolic alterations 23 , recent studies have indicated that this response is cultivar dependent 24 . Our hypothesis is further reinforced by the Varpart analysis, which showed a greater contribution of host cultivar to the bacterial assemblage in OK-symptomatic twigs (24.4%) when compared to asymptomatic twigs (2.5%), as similarly observed for the fungal community in the same olive tree cultivars 16 . The role of host plant in structuring both rhizosphere and root endosphere bacterial communities in response to a pathogen www.nature.com/scientificreports www.nature.com/scientificreports/ attack was already reported 25,26 .…”

“…Thus, the olive cultivar seems to influence the establishment of pathobiome communities in olive knots. Accordingly, previous studies have suggested that differences on microbial abundance and diversity between asymptomatic and symptomatic tissues were possibly related to the susceptibility of the plant host to a certain disease 16,[18][19][20][21] . We hypothesized that the detected greater differences in the bacterial composition of OK-susceptible cv.…”

“…Changes in bacterial diversity and composition between asymptomatic and OK-symptomatic twigs were greater for endophytes than for epiphytes, thus suggesting a greater sensitivity of endophytes to Pss infection. While no comparative studies are available considering the effect of a plant disease in host bacterial epiphytic and endophytic community composition, Gomes et al 16 obtained an opposite result with fungal communities, being epiphytes more affected by bacterial disease than endophytes. Furthermore, we have detected distinct changes on endophytic communities from both cultivars.…”

Differences in the Endophytic Microbiome of Olive Cultivars Infected by Xylella fastidiosa across Seasons

“…Studies of fungal endophyte communities in olive were mainly performed in aboveground organs by using cultivation-dependent methods [ 42 , 43 , 44 , 45 ], while metabarcoding analysis was less frequently used. All these studies indicated Ascomycota as the most abundant fungal endophytes in olive leaves, twigs, and fruits.…”

Fungal alpha-diversity drives the stochasticity of bacterial and fungal community assembly in soil aggregates in the apple orchard

“…Bacteria and fungi naturally coexist in various environments, and their cooperation or antagonistic interactions are widely demonstrated for humans, plants, aquatic and soil ecosystems and signi cantly impact their functions (Das et al, 2012;Gomes et al, 2019). Since soil bacteria and fungi are the major components of soil ecosystems, exploration of the bacterial and fungal community diversities and compositions and their co-exist patterns in different sizes of spatial habitats in the soil is primarily important for revealing the mechanism of change of bacterial and fungal diversity and composition in the whole soil.…”