Exogenous double‐stranded RNA inhibits the infection physiology of rust fungi to reduce symptoms in planta

Abstract

Rust fungi (Pucciniales) are a diverse group of plant pathogens in natural and agricultural systems. They pose ongoing threats to the diversity of native flora and cause annual crop yield losses. Agricultural rusts are predominantly managed with fungicides and breeding for resistance, but new control strategies are needed on non-agricultural plants and in fragile ecosystems. RNA interference (RNAi) induced by exogenous double-stranded RNA (dsRNA) has promise as a sustainable approach for managing plant-pathogenic fungi, including rust fungi. We investigated the mechanisms and impact of exogenous dsRNA on rust fungi through in vitro and whole-plant assays using two species as models, Austropuccinia psidii (the cause of myrtle rust) and Coleosporium plumeriae (the cause of frangipani rust). In vitro, dsRNA either associates externally or is internalized by urediniospores during the early stages of germination. The impact of dsRNA on rust infection architecture was examined on artificial leaf surfaces. dsRNA targeting predicted essential genes significantly reduced germination and inhibited development of infection structures, namely appressoria and penetration pegs. Exogenous dsRNA sprayed onto 1-year-old trees significantly reduced myrtle rust symptoms. Furthermore, we used comparative genomics to assess the wide-scale amenability of dsRNA to control rust fungi. We sequenced genomes of six species of rust fungi, including three new families (Araucariomyceaceae, Phragmidiaceae, and Skierkaceae) and identified key genes of the RNAi pathway across 15 species in eight families of Pucciniales. Together, these findings

Differential aggressiveness of Austropuccinia psidii isolates from guava and rose apple upon cross‐inoculation

“…The pathogenic characterization of the isolates used in this work corroborates the results based on genetic similarity that separate two well-structured populations of A. psidii of Brazilian origin into two different biotypes: from guava and from rose apple or eucalyptus.High percentages of urediniospore germination were observed in all experiments. Similar rates of urediniospore germination and appressorium formation were observed in A. psidii on both rose apple leaves and artificial membranes(Degnan et al, 2023). Nevertheless, the percentage of appressoria formation was lower on the RG than F I G U R E 4 Comparison of the progress of leaf colonization of Austropuccinia psidii isolates from guava (RG combination) and rose apple (RR combination) on rose apple leaf.…”

“…Similar rates of urediniospore germination and appressorium formation were observed in A . psidii on both rose apple leaves and artificial membranes (Degnan et al., 2023). Nevertheless, the percentage of appressoria formation was lower on the RG than on the RR combination, which resulted in lower density of lesions on RG when compared to RR.…”

Effectively enhancing topical delivery of agrochemicals onto plant leaves with nanocelluloses

“…PDMS (polydimethylsiloxane) and PDMS with PVP treatment were kindly supplied by the Queensland Alliance for Agriculture and Food Innovation (QAAFI, Australia). 12 The cotton ( Gosssypium ), chickpea ( Cicer arietinum ), and sweet corn ( Zea mays L. var. rugosa Bonaf. )…”