Maushe, Dorothy (2025). Adaptations of entomopathogenic nematodes to plant-derived benzoxazinoids. (Thesis). Universität Bern, Bern

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Abstract

Benzoxazinoids (BXs) are plant specialized metabolites involved in herbivore-defenses of cereals such as maize and wheat. The Western Corn Rootworm (WCR, Diabrotica virgifera virgifera), a specialist root herbivore, stabilizes, sequesters and accumulate them into their bodies. The interactions of these WCR accumulated toxins with the WCR natural enemies, entomopathogenic nematodes (EPNs) are not fully understood. This thesis aimed to investigate EPN benzoxazinoid tolerance and resistance mechanisms and or strategies. Chapter 2 demonstrated using an evolutionary experiment that EPNs evolved BX resistance within three host cycles. Additionally, we also found that before adaptation, BX repulsive effect can explain the initial differences between BX- sensitive and Bx resistance isolates. However, this phenomenon (repulsion) cannot explain difference between BX-adapted and non-adapted isolates. These findings highlight the capacity of EPNs to rapidly adapt to plant chemical defenses, providing new insights into enhancing the efficacy of biocontrol strategies against BX-sequestering pests like WCR. Chapter 3, revealed that EPNs can fight back benzoxazinoid toxin effects by biodegrading them to their breakdown derivates, thus, showing EPNs ability to respond in stressful situations. This work findings will be helpful in elucidation mechanistic bases of inter- strain benzoxazinoid tolerance variation. Additionally, this will make prediction of benzoxazinoid effect on various strains possible. Furthermore, this paves way for nematode breeders for development of genetic markers linked benzoxazinoid tolerance. Chapter 4, indicated cooperative acts between EPN and some of its associates in times of trouble which may in turn benefit the EPN to grow, develop and survive in stressful situations. These findings will motivate nematologists to study and understand other symbiosis relationships between EPNs and their associates. Understanding the influences of such EPN associations in EPN biological, physiological and biochemical process may give crucial information for EPN-contents manipulations programs, which may be used in maximizing EPN- control potential and protection.

Item Type:	Thesis
Dissertation Type:	Cumulative
Date of Defense:	19 May 2025
Subjects:	500 Science > 570 Life sciences; biology 500 Science > 580 Plants (Botany)
Institute / Center:	08 Faculty of Science > Department of Biology > Institute of Plant Sciences (IPS)
Depositing User:	Sarah Stalder
Date Deposited:	02 Jun 2025 11:22
Last Modified:	02 Jun 2025 11:22
URI:	https://boristheses.unibe.ch/id/eprint/6236

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