Gene‐for‐gene relationship in the host–pathogen system Malus × robusta 5–Erwinia amylovora

Abstract

SummaryFire blight is a destructive bacterial disease caused by Erwinia amylovora affecting plants in the family Rosaceae, including apple. Host resistance to fire blight is present mainly in accessions of Malus spp. and is thought to be quantitative in this pathosystem.In this study we analyzed the importance of the E. amylovora effector avrRpt2 EA , a homolog of Pseudomonas syringae avrRpt2, for resistance of Malus 9 robusta 5 (Mr5).The deletion mutant E. amylovora Ea1189DavrRpt2 EA was able to overcome the fire blight resistance of Mr5. One single nucleotide polymorphism (SNP), resulting in an exchange of cysteine to serine in the encoded protein, was detected in avrRpt2 EA of several Erwinia strains differing in virulence to Mr5. E. amylovora strains encoding serine (S-allele) were able to overcome resistance of Mr5, whereas strains encoding cysteine (C-allele) were not. Allele specificity was also observed in a coexpression assay with Arabidopsis thaliana RIN4 in Nicotiana benthamiana. A homolog of RIN4 has been detected and isolated in Mr5.These results suggest a system similar to the interaction of RPS2 from A. thaliana and AvrRpt2 from P. syringae with RIN4 as guard. Our data are suggestive of a gene-for-gene relationship for the host-pathogen system Mr5 and E. amylovora.

Identification of apple miRNAs and their potential role in fire blight resistance

“…The best-known effect of rootstock is on tree stature (Wertheim 1998), but rootstock effect on scion disease susceptibility was also reported (Fallahi et al 2002). Therefore, using fire blight-resistant rootstocks might be the most promising strategy for protection of apple trees (Kellerhals et al 2009;Norelli et al 2003;Vogt et al 2013). The mechanism by which rootstock affects tree phenotype is not known, but it clearly influences gene expression pattern of their scion.…”

“…Fire blight (FB) is a contagious bacterial disease caused by Gram-negative bacteria Erwinia amylovora that affects apples and pears and leads to considerable reduction in fruit production worldwide (Vogt et al 2013). Its incidence has increased in commercial apple orchards over the last 25 years (Norelli et al 2003).…”

Whole-Genome Sequencing of Erwinia amylovora Strains from Mexico Detects Single Nucleotide Polymorphisms in rpsL Conferring Streptomycin Resistance and in the avrRpt2 Effector Altering Host Interactions

“…The identical variant avrRpt2 occurs in strains from Ontario, Michigan, and West Virginia but not elsewhere. This mutation enables E. amylovora to overcome the unique disease resistance recently described in Malus × robusta 5, a wild apple used in breeding programs (12). Genotyping based on clusters of regularly interspaced short palindromic repeat (CRISPR) sequences (13) and the avrRpt2 SNP (12) suggest northeastern North America as the origin of the fire blight pathogen in Mexico (2, 3).…”

Genetically modified crops in Switzerland: implications for agrosystem sustainability evidenced by multi-criteria model

“…Firstly, the amounts of subsidies (direct payments) were postulated as similar for GM crops as for conventional ones. Secondly, the appearance of weeds tolerant to HT plants (Brookes and Barfoot 2013;Green 2014), insect resistance for Bt species, apple scab, or fire blight resistances were not monitored here despite their reported occurrence (Vogt et al 2013;Fahrentrapp et al 2013;Jin et al 2015) but were nonetheless discussed. MCDA and more generally multiattribute models are not directly suitable for time-series evaluation (Bohanec et al 2008).…”

“…Resistance to fire blight in apple is thought to be a gene-to-gene relationship and therefore easily overcome by the parasite. For example, some E. amylovora strains have overcome the resistance of cultivar MR5 in a couple of years via single point mutations (Vogt et al 2013). The complexity of host/pathogen relationship makes likely to be necessary (1) a coordinated research effort to understand mechanisms used, (2) a tailored design of resistance genes/mechanisms to be introgressed into the new GM event and finally (3) an adaptive crop management system.…”