The structure and function of rhizosphere microbial communities are affected by the plant health status. In this study, we investigated the effect of root rot on the avocado rhizosphere microbiome, ...using 16S rDNA and ITS sequencing. Furthermore, we isolated potential fungal pathogens associated with root rot symptoms and assessed their pathogenic activity on avocado. We found that root rot did not affect species richness, diversity or community structure, but induced changes in the relative abundance of several microbial taxa. Root rot increased the proportion of Pseudomonadales and Burkholderiales in the rhizosphere but reduced that of Actinobacteria,
spp. and Rhizobiales. An increase in putative opportunistic fungal pathogens was also detected in the roots of symptomatic trees; the potential pathogenicity of
sp.,
spp.,
sp. and
sp., is reported for the first time for the State of Veracruz, Mexico. Root rot also potentially modified the predicted functions carried out by rhizobacteria, reducing the proportion of categories linked with the lipid and amino-acid metabolisms whilst promoting those associated with quorum sensing, virulence, and antibiotic resistance. Altogether, our results could help identifying microbial taxa associated to the disease causal agents and direct the selection of plant growth-promoting bacteria for the development of biocontrol microbial consortia.
The decline of honey bee populations significantly impacts the human food supply due to poor pollination and yield decreases of essential crop species. Given the reduction of pollinators, research ...into critical landscape components, such as floral resource availability and land use change, might provide valuable information about the nutritional status and health of honey bee colonies. To address this issue, we examine the effects of landscape factors like agricultural area, urban area, and climatic factors, including maximum temperature, minimum temperature, relative humidity, and precipitation, on honey bee hive populations and nutritional health of 326 honey bee colonies across varying landscapes in Mexico. DNA metabarcoding facilitated the precise identification of pollen from 267 plant species, encompassing 243 genera and 80 families, revealing a primary herb‐based diet. Areas characterized by high landscape diversity exhibited greater pollen diversity within the colony. Conversely, colonies situated in regions with higher proportions of agricultural and urban landscapes demonstrated lower bee density. The maximum ambient temperature outside hives positively correlated with pollen diversity, aligning with a simultaneous decrease in bee density. Conversely, higher relative humidity positively influenced both the bee density of the colony and the diversity of foraged pollen. Our national‐level study investigated pollen dietary availability and colony size in different habitat types, latitudes, climatic conditions, and varied levels and types of disturbances. This effort was taken to gain a better insight into the mechanisms driving declines in honey bee populations. This study illustrates the need for more biodiverse agricultural landscapes, the preservation of diverse habitats, and the conservation of natural and semi‐natural spaces. These measures can help to improve the habitat quality of other bee species, as well as restore essential ecosystem processes, such as pollination and pest control.
This study investigates how landscape diversity and climatic factors affect the populations and nutritional health of honey bee colonies in Mexico. It was found that greater landscape diversity correlates with higher pollen diversity, while areas with more agriculture and urbanization show lower bee densities. The results underscore the importance of preserving diverse habitats to support bee health and, by extension, human food security.
Abstract
Background
Rhizosphere microbiomes are fundamental for plant health, development, and productivity, but can be altered by the incidence of soil-borne pathogens. The dysbiosis (disturbance of ...the microbiome structure of healthy plants) caused by these pathogens, combined with the recruitment of beneficial microorganisms by the diseased plant, may cause shifts in the rhizosphere microbiome during the infection process. These shifts are likely to be associated with changes in the rhizosphere metabolic profile, as the biochemical dialog, or crosstalk, between host plants and their microbiome is mostly mediated by root exudates. Our objective was to elucidate the shifts in the avocado rhizosphere microbiome and associated changes in the rhizosphere metabolome induced by the infection of the oomycete
Phytophthora cinnamomi
. We also evaluated the effect of inoculating a bacterial biological control agent (BCA) of
P. cinnamomi
on the avocado rhizosphere microbiome, in the presence and absence of the pathogen, and on morphological and physiological plant variables, to confirm the potential of the BCA to alleviate the stress induced by the disease.
Dataset presentation
Here, we present a novel dataset collected from a time-course experiment with four treatments: (1) control trees; (2) trees infected with
P. cinnamomi
; (3) trees inoculated with the BCA; (4) trees infected with
P. cinnamomi
and inoculated with the BCA. During the infection process, we measured plant morphological and physiological variables and collected rhizosphere soil samples for bacterial and fungal amplicon sequencing, bacterial RNA-seq and metabolomic analyses.
Conclusions
Collectively, our data elucidate the shifts in the avocado rhizosphere microbiome after infection by
P. cinnamomi
and when inoculated with a BCA, and help understand how a pathogen or a beneficial bacterium can alter plant-microbiome crosstalk. Understanding the effect of
P. cinnamomi
or a BCA on the avocado tree physiology and on the avocado rhizosphere microbiome and metabolome will direct our search for disease biomarkers or potential pathogen antagonists, help identify metabolites related to the recruitment of microorganisms, and assist us in developing integrated disease management strategies.
Hybridization is commonly reported in angiosperms, generally based on morphology, and in few cases confirmed by molecular markers.
has a long tradition of ornamental cultivars with different hybrids ...produced by artificial crosses, so natural hybridization between sympatric
species could be common. Natural hybridization between
and
was tested using six newly developed microsatellites for
in addition to other molecular markers with codominant and maternal inheritance. Geometric morphometrics of leaves and floral structures were also used to identify putative hybrids. Hybrids showed a different degree of genetic admixture between both parental species. Chloroplast DNA (cpDNA) sequences indicated that hybridization occurs in both directions, in fact, some of the hybrids showed new haplotypes for cpDNA and ITS (internal transcriber spacer of nuclear ribosomal RNA genes) sequences. The morphology of hybrid individuals varied between the two parental species, but they could be better identified by their leaves and floral tubes. Our study is the first to confirm the hybridization in natural populations of
species and suggests that hybridization has probably occurred repeatedly throughout the entire distribution of the species. Phylogeographic analysis of both species will be essential to understanding the impact of hybridization throughout their complete distribution.
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