Doctoral thesis (Dissertations and theses)
Impact of endophytic entomopathogenic fungi in Plant–aphid–virus relationships
Fingu Mabola, Junior Corneille
2021
 

Files


Full Text
MyThesis_FORMATED_FINAL_to_Print.pdf
Author postprint (3.3 MB)
Request a copy

All documents in ORBi are protected by a user license.

Send to



Details



Abstract :
[en] Entomopathogenic fungi (EPF) are biological control agents widely used as alternatives to synthetic chemicals to protect plants against pests. Particularly, filamentous EPF are sometimes applied by inundative method and are effective to control phloem-feeding insects, including aphids, most important vector of plant viruses. These EPF infect their hosts cutaneously, invade their internal cavity until death, then sporulate on the cadaver and spread to reach other insect hosts. Several studies have highlighted the endophytic behaviour of filamentous EPF. Indeed, they colonise plant tissues spending at least a part of their life cycle without symptoms appearance. Thus, several studies report that endophytic entomopathogenic fungi (EEPF) improves plant growth, enhance the immune system and interact with plant enemies including plant pathogens, insect pests, but also beneficials. The objective of this thesis was to evaluate the impact of EEPF on a vector-borne plant virus pathosystem. This, was based on the hypothesis that physiological changes in the plant as a result of EEPF colonisation of its tissues would have an impact on aphid (vector) behaviour and then influence the plant virus spread. Two pathosystems were used: (1) tobacco (Nicotiana tabacum L.), one of the host plants of potato leafroll virus (PLRV) transmitted by Myzus persicae Sulzer (Hemiptera: Aphididae) and (2) wheat (Triticum aestivum L.), host of barley yellow dwarf virus (BYDV) transmitted by Rhopalosiphum padi L. (Hemiptera: Aphididae); and two EPF species: (1) Beauveria bassiana GHA and (2) Metarhizium acridum IMI330189. The study was carried out in three research axis described in the following paragraphs. Previously, (1) the functioning of the plant–aphid–virus pathosystem was studied in order to identify the targets to be analysed in the context of the interaction between the pathosystem and the EPF. Then, the host-seeking behaviour (HSB), life history traits (LHT) and vectorial transmission efficiency (VTE) of the vector were selected for further investigations. Then, (2) experiments were conducted trying to inoculate the EPF on model plants of the pathosystems under study and techniques have been optimised. Knowing that the HSB of aphids justifies in large part their capacity to spread plant viruses, the first axis of the study aimed to evaluate the aphid behaviour when carrying or not carrying plant viruses in response to three plant modalities: healthy, virus-infected and EEPF-colonised. Choice tests in Petri dishes arena were carried out on the two pathosystems, but also sampling and analysis of volatile organic compound (VOC) profiles of the three plant modalities were performed in order to assess the aphid preferences observed during choice tests. We found that aphids were influenced by their infection status when choosing between virus-infected and non-infected plants. In contrast, aphids carrying and not carrying plant virus were all attracted to EEPF-colonised compared to non-colonised plants. Finally, the aphids that were not carrying plant virus had no preference between a virus-infected and an EEPF-colonised plant, whereas the aphids carrying plant virus maintained their choice on EEPF-colonised plants. The VOC analysis confirmed that the volatile profile emitted by the plants was altered as a consequence of EEPF colonisation in their tissues. In the second research axis, aphid life history traits when settled on EEPF-colonised host plant were evaluated. Furthermore, analyses were carried out to compare the efficacy of the systemic effect due to endophytism, the classical contact treatment of EPF and a potential interaction between the two modes of action and the infectious status of the plant virus vector. A synergistic effect between the presence of EEPF in plant tissues and the infectious status of the insect was found. Indeed, aphids carrying plant viruses were more vulnerable in relation with EPF treatment than those not carrying plant viruses. In addition, fecundity and mortality rate of nymphs were negatively and positively correlated with the EEPF-colonisation rate of leaf tissue, respectively. The third research axis focused on plant viruses spread on EEPF-colonised compared to non-colonised plants. The objective was to analyse the impact of EEPF on aphid vectorial competence in relation to its host plant and the plant virus it carries. Experiments implemented with the Tobacco – M. persicae – PLRV pathosystem consisted in releasing aphids on source plants previously inoculated with EEPF or not and then transferring them to EEPF-colonised or not-colonised recipient plants. Samples were collected in three incubation periods to assess the virus spread rate in the different plant treatments. We found that the rate of infection was low for EEPF-colonised plants at the early incubation time compared to not-colonised plants, and evolved over time to have similar results at the late incubation time. At the end of the experiment, almost all plants were positive for plant virus regardless of the treatment. This study is among the first to focus on the impact of the endophytic behaviour of EPF in a plant virus pathosystem, especially on plant virus spread. It provides interesting results on aphid behaviour in response to an EEPF-colonised plant, especially their host-seeking behaviour, their performance when settled on these plants and their ability to transmit virus on the same plants.
Disciplines :
Entomology & pest control
Author, co-author :
Fingu Mabola, Junior Corneille ;  Université de Liège - ULiège > TERRA Research Centre
Language :
English
Title :
Impact of endophytic entomopathogenic fungi in Plant–aphid–virus relationships
Alternative titles :
[fr] Impact des champignons entomopathogènes endophytes sur les interactions Plante–Insecte–Phytovirus
Defense date :
08 July 2021
Number of pages :
151
Institution :
ULiège - Université de Liège
Degree :
Sciences agronomiques et ingénierie biologique
Promotor :
Francis, Frédéric  ;  Université de Liège - ULiège > GxABT : Services généraux du site > Site GxABT - Relations internationales
President :
Jacques, Philippe ;  Université de Liège - ULiège > Département GxABT > Microbial, food and biobased technologies
Jury member :
Massart, Sébastien  ;  Université de Liège - ULiège > Département GxABT > Gestion durable des bio-agresseurs
Delvigne, Frank  ;  Université de Liège - ULiège > Département GxABT > Microbial, food and biobased technologies
Verheggen, François  ;  Université de Liège - ULiège > Département GxABT > Gestion durable des bio-agresseurs
Seye, Fawrou
Bawin, Thomas
Available on ORBi :
since 02 July 2021

Statistics


Number of views
226 (32 by ULiège)
Number of downloads
15 (13 by ULiège)

Bibliography


Similar publications



Contact ORBi