Partially Resistant Avocado Rootstock Dusa Shows Prolonged Upregulation of Genes in Response to Infection.

Avocado is an important agricultural food crop in many countries worldwide. , a hemibiotrophic oomycete, remains one of the most devastating pathogens within the avocado industry, as it is near impossible to eradicate from areas where the pathogen is present. A key aspect to Phytophthora root rot disease management is the use of avocado rootstocks partially resistant to , which demonstrates an increased immune response following infection. In plant species, Nucleotide binding-Leucine rich repeat (NLR) proteins form an integral part of pathogen recognition and Effector triggered immune responses (ETI). To date, a comprehensive set of genes have yet to be identified, though their discovery is crucial to understanding the molecular mechanisms underlying interactions. In this study, a total of 161 genes were identified in the West-Indian pure accession genome. These putative resistance genes were characterized using bioinformatic approaches and grouped into 13 distinct gene clusters, with phylogenetic analysis revealing high sequence similarity within these clusters. Additionally, expression levels were analyzed in both a partially resistant (Dusa®) and a susceptible (R0.12) avocado rootstock infected with using an RNA-sequencing approach. The results showed that the partially resistant rootstock has increased expression levels of 84 observed up to 24 h post-inoculation, while the susceptible rootstock only showed increased expression during the first 6 h post-inoculation. Results of this study may indicate that the partially resistant avocado rootstock has a stronger, more prolonged ETI response which enables it to suppress growth and combat disease caused by this pathogen. Furthermore, the identification of may be used to develop resistant rootstock selection tools, which can be employed in the avocado industry to accelerate rootstock screening programs.