Biology subjects

Merckx, V.

Publications and source records attributed to Merckx, V..

5 recordsLinked to original sources

bioRxiv2021

Genetic diversity of the pathogenic banana Fusarium wilt in northern Viet Nam

Fusarium is one of the most important fungal genera of plant pathogens that affect the cultivation of a wide range of crops. Agricultural losses caused by Fusarium oxysporum f. sp. cubense (Foc) have a direct effect on the income, subsistence and nourishment of thousands of smallholder farmers worldwide. In addition, also commercial growers are strongly affected. For Viet Nam, predictions on the impact of Foc for the future are dramatic with an estimated loss in banana production area of 8% within the next 5 years and up to 71% within the next 25 years. In the current study we applied a combined morphological - molecular approach to assess the taxonomic identity and phylogenetic position of the different Foc isolates that were collected in northern Viet Nam. In addition, we aim to estimate the proportion of the different Fusarium races that are infecting bananas in northern Viet Nam. The morphology of the isolates was investigated by growing the collected Fusarium isolates on four distinct nutritious media (PDA, SNA, CLA, and OMA). Molecular phylogenetic relationships were inferred by sequencing partial rpb1, rpb2 and tef1a genes and adding the obtained sequences into a large phylogenetic framework. The present study showed that Foc Race 1 is the most common strain in northern Viet Nam, causing 74% of all the infections. A more in-depth molecular characterization shows that of the Foc Race 1 infections, 92% are caused by Fusarium tardichlamydosporum and 8% by F. duoseptatum. Compared to Foc Race 1, Foc TR4 (represented by F. odoratissimum) account for only 10.5% of the Fusarium wilting in northern Viet Nam demonstrating that Foc TR4 is not yet a dominant strain in the region. Foc Race 2 infections of Vietnamese bananas also account for 10.5% of the Fusarium wilting in northern Viet Nam. One of the isolates cultured from diseased bananas collected in northern Viet Nam was phylogenetically not positioned within the F. oxysporum species complex (FOSC), but in contrast fell within the Fusarium fujikuroi species complex (FFSC). As a result, it is possible that a new pathogen for bananas has been found. Besides being present on several ABB Tay banana, Foc Race 1 was also found as pathogen on wild Musa lutea, showing the importance of wild bananas as possible sink for Foc.

evolutionary biology↗

bioRxiv2020

Multiple origins of insular woodiness on the Canary Islands are consistent with palaeoclimatic aridification

AimInsular woodiness, referring to the evolutionary transition from herbaceousness towards woodiness on islands, has arisen at least 38 times on the Canary Islands. Distribution patterns and physiological experiments have suggested a link between insular woodiness and increased drought stress resistance in current-day species, but we do not know in which palaeoclimatic conditions these insular woody lineages originated. Therefore, we estimated the timing of colonisation events and origin of woodiness of multiple Canary Island lineages and reviewed the palaeoclimate based on literature. LocationCanary Islands (Spain). Taxon37 lineages, including 24 insular woody and 13 non-insular woody (i.e. herbaceous, ancestrally woody, and derived woody). MethodsTo enable a simultaneous dating analysis for all 37 lineages, two chloroplast markers (matK and rbcL) for 135 Canary Island species and 103 closely related continental relatives were sequenced and aligned to an existing matK-rbcL dataset including ca 24,000 species that was calibrated with 42 fossils from outside the Canaries. After constraining the species to the family level, 200 RAxML runs were performed and dated with TreePL. ResultsWoodiness in 80-90% of the insular woody lineages originated within the last 7 Myr, coinciding with the onset of major aridification events nearby the Canaries (start of north African desertification, followed by Messinian salinity crisis); in ca 55-65% of the insular woody lineages studied, woodiness developed within the last 3.2 Myr during which Mediterranean seasonality (yearly summer droughts) became established on the Canaries, followed by dry Pleistocene glacial fluctuations. Main conclusionsAlthough details of the initial colonisation and settlement of many island plant lineages remain elusive, our results are consistent with palaeodrought as a potential driver for woodiness in most of the insular woody Canary Island lineages studied.

evolutionary biology↗

bioRxiv2019

Plant cheaters preferentially target arbuscular mycorrhizal fungi that are highly connected to mutualistic plants

O_LIHow antagonists - mycoheterotrophic plants that obtain carbon and soil nutrients from fungi - are integrated in the usually mutualistic arbuscular mycorrhizal networks is unknown. Here, we compare mutualistic and antagonistic plant associations with arbuscular mycorrhizal fungi and use network analysis to investigate fungal association preferences in the tripartite network. C_LIO_LIWe sequenced root tips from mutualistic and antagonistic plants in a tropical forest to assemble the combined tripartite network between mutualistic plants, mycorrhizal fungi, and antagonistic plants. We compared the fungal ecological similarity between mutualistic and antagonist networks, and searched for modules (an antagonistic and a mutualistic plant interacting with the same pair of fungi) to investigate whether pairs of fungi simultaneously linked to plant species from each interaction type were overrepresented throughout the network. C_LIO_LIAntagonistic plants interacted with approximately half the fungi detected in mutualistic plants. Antagonists were indirectly linked to any of the detected mutualistic plants, and fungal pairwise ecological distances were correlated in both network types. Moreover, pairs of fungi sharing the same antagonistic and mutualistic plant species occurred more often than expected by chance. C_LIO_LIWe hypothesize that the maintenance of antagonistic interactions is maximized by targeting well-linked mutualistic fungi, thereby minimizing the risk of carbon supply shortages. C_LI

ecology↗

bioRxiv2019

A large-scale species level dated angiosperm phylogeny for evolutionary and ecological analyses

Phylogenies are a central and indispensable tool for evolutionary and ecological research. Even though most angiosperm families are well investigated from a phylogenetic point of view, there are far less possibilities to carry out large-scale meta-analyses at order level or higher. Here, we reconstructed a large-scale dated phylogeny including nearly 1/8th of all angiosperm species based on two plastid barcoding genes, matK and rbcL. Novel sequences were generated for several species, while the rest of the data were mined from GenBank. The resulting tree was dated using 56 angiosperm fossils as calibration points. The resulting megaphylogeny is one of the largest dated phylogenetic tree of angiosperms yet, consisting of 36,101 sampled species, representing 8,399 genera, 426 families and all orders. This novel framework will be useful to investigate different broad scale research questions in ecological and evolutionary biology.

evolutionary biology↗

bioRxiv2019

FungalRoot: Global online database of plant mycorrhizal associations

O_LIThe urgent need to better understand profound impacts of mycorrhizas on functioning of terrestrial ecosystems, along with recent debates on resolving plant mycorrhizal associations, indicate that there is a great need for a comprehensive data of plant mycorrhizal associations able to support testing of ecological, biogeographic and phylogenetic hypotheses.\nC_LIO_LIHere present a database, FungalRoot, which summarizes publicly available data on plant mycorrhizal type and intensity of root colonization by mycorrhizal fungi, accompanied by rich meta-data. We collected and digitized data on plant mycorrhizal colonization intensity published until April 2019 in 9 globally most important languages. The data were assessed for quality and updated for plant taxonomy.\nC_LIO_LIThe FungalRoot database contains 36,303 species by site observations for 14,870 plant species, tripling the previously available amount in any compilation. The great majority of ectomycorrhizal and ericod mycorrhizal plants are trees and shrubs, 92% and 85% respectively. The majority of arbuscular mycorrhizal and of non-mycorrhizal plant species are herbaceous (50% and 70%).\nC_LIO_LIBesides acting as a compilation of referenced observations, our publicly available database provides a recommendation list of plant mycorrhizal status for ecological and evolutionary analyses to promote research on the links between above- and belowground biodiversity and functioning of terrestrial ecosystems.\nC_LI

ecology↗