Elicitors of the salicylic acid pathway reduce incidence of bacterial canker of kiwifruit caused by Pseudomonas syringae pv. actinidae

Abstract

Some strains of Pseudomonas syringae pv. actinidiae (Psa), the causal agent of bacterial canker of kiwifruit, produce plant hormones and toxins which alter the plant hormonal balance and result in the suppression of the salicylic acid (SA)-dependent plant defences. To determine whether Psa could be affected by stimulation of the SA pathway, Actinidia deliciosa and A. chinensis were treated with compounds which interfere with this pathway, then inoculated with Psa. On A. deliciosa, compounds which stimulate the SA pathway [SA, or its synthetic analogue, acibenzolar-S-methyl (ASM)] or close stomata (ABA) resulted in disease reduction, while methyl-jasmonate (MJA) or ethylene increased disease development. On A. chinensis, similar results were obtained except that SA and MJA did not affect disease development. Reduction in disease incidence and severity on A. deliciosa using ASM was correlated with a superoxide burst, the formation of necrotic spots and callose deposition, while on A. chinensis no superoxide burst or callose deposition was detected. Genes involved in plant-pathogen interactions were induced after treatment with ASM in A. deliciosa and, to a lesser extent, in A. chinensis. Those differences in gene expression and physiological responses after treatment with ASM are consistent with the different susceptibility to Psa observed between A. chinensis and A. deliciosa.

Biological control of bacterial plant diseases with Lactobacillus plantarum strains selected for their broad‐spectrum activity

“…Overall, reliance on conventional pesticides needs to be reduced and an integrated pest management (IPM) framework implemented (Lamichhane et al, ). The plant defence elicitor acibenzolar‐S‐methyl (ASM) has been reported as being a potential alternative compound for managing bacterial canker of kiwifruit (Cellini et al, ) and angular leaf spot of strawberry (Braun & Hildebrand, ). Likewise, chitosan exhibits antimicrobial activity and acts as an elicitor of plant defence mechanisms, making it a potential alternative agent for managing bacterial canker of kiwifruit (Cameron & Sarojini, ).…”

Multiple quantitative trait loci contribute tolerance to bacterial canker incited by Pseudomonas syringae pv. actinidiae in kiwifruit (Actinidia chinensis)

“…Many environmental factors differ in greenhouse and in in vitro growth conditions compared to the field so might contribute to the plasticity of plant phenotypic responses. This includes factors such as temperature 53–55 , humidity 56–60 , other microbial communities in the field, as well as physiological changes during the growth and aging of A. chinensis vines may have an effect. In the future, elucidation of the role of the genetic loci regulating the observed tissue-specific responses to Psa infection will be helpful in determining the dynamics of the host-pathogen relationship in the disease triangle of the A. chinensis / Psa patho-system 61 .…”

Exploring the expression of defence-related genes in Actinidia spp. after infection with Pseudomonas syringae pv. actinidiae and pv. actinidifoliorum: first steps

“…Estimation of bacterial colony forming units (CFUs) was performed using an adapted method from Cellini et al (2014). Samples were surface sterilised by washing in 70% ethanol for 1 min, followed by a 1-min treatment with 1% sodium hypochlorite, after which they were rinsed twice in sterile water for 1 min.…”

“…Plant RNA was extracted according to an adapted protocol from Cellini et al (2014). After tissue homogenization with liquid nitrogen, 1 mL of warm (70°C) extraction buffer (100 mM Tris-HCl, pH 8.0, cetyltrimethylammonium bromide 4% w/v, polyvinylpyrrolidone K40 4% w/v, 30 mM ethylenediamine tetraacetic, 2.0 M NaCl, spermidine 0.1% w/v, -mercaptoethanol 2% v/v) was added to ca.…”