Van den Berg, Noelani2025-01-292025-01-292025-042024-11*A2025http://hdl.handle.net/2263/100387Dissertation (MSc (Genetics))--University of Pretoria, 2024.Avocado (Persea americana) production is threatened by Phytophthora cinnamomi, the causative agent of Phytophthora root rot (PRR). Current control measures rely on phosphite-based fungicides and partially-resistant rootstocks like Dusa®. However, the immune mechanisms underlying Dusa®'s resistance remain unclear. This study investigated nucleotide-binding leucine-rich repeat (NLR) proteins in Dusa®, which play a critical role in effector-triggered immunity (ETI) and hypersensitive response (HR). Using a Nicotiana benthamiana-P. cinnamomi model system, we identified the biotrophic and necrotrophic phases of infection, applying this knowledge to study avocado NLRs. Six PaNLR candidates were selected based on expression patterns, defense motifs, and effector recognition potential. Transient expression assays revealed that five PaNLRs caused HR only upon pathogen introduction, while one induced cell death independently. Cellular localization studies showed most PaNLRs reside in the nucleus during the resting stage, with one in the cytoplasm. Upon P. cinnamomi infection, all candidates triggered a strong HR, effectively restricting pathogen spread. These findings suggest that PaNLRs adopt diverse strategies to induce immunogenic cell death, balancing resource conservation and rapid defense activation. This study provides the first molecular characterization of PaNLRs, offering insights into avocado immunity and pathways for enhancing resistance in this economically important crop.en© 2023 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.UCTDSustainable Development Goals (SDGs)Phytophthora root rot (PRR)Avocado NLR proteinsDusa® rootstock resistanceEffector-triggered immunity (ETI)Hypersensitive response (HR)Nicotiana benthamiana modelDissertationu19071443https://10.25403/UPresearchdata.28296932