Identification of serine/threonine kinase and nucleotide‐binding site–leucine‐rich repeat (NBS‐LRR) genes in the fire blight resistance quantitative trait locus of apple cultivar ‘Evereste’

Abstract

Fire blight is the most destructive bacterial disease affecting apple (Malus×domestica) worldwide. So far, no resistance gene against fire blight has been characterized in apple, despite several resistance regions having been identified. A highly efficacious resistance quantitative trait locus (QTL) was localized on linkage group 12 (LG12) of the ornamental cultivar 'Evereste'. A marker previously reported to be closely linked to this resistance was used to perform a chromosome landing. A bacterial artificial chromosome (BAC) clone of 189 kb carrying the fire blight resistance QTL was isolated and sequenced. New microsatellite markers were developed, and the genomic region containing the resistance locus was limited to 78 kb. A cluster of eight genes with homologies to already known resistance gene structures to bacterial diseases was identified and the corresponding gene transcription was verified. From this cluster, two genes were recognized in silico as the two most probable fire blight resistance genes showing homology with the Pto/Prf complex in tomato.

Use of a transgenic early flowering approach in apple (Malus × domestica Borkh.) to introgress fire blight resistance from cultivar Evereste

“…Inheritance of the BpMADS4 transgene from the transgenic line T1190 to the F1 and BC 0 1 progenies was followed using the specific primers named BpMADS4_F and BpMADS4_R developed from the transgene's sequence, with the PCR conditions as described previously ). Inheritance of the fire blight resistance locus Fb_E from the ornamental apple cultivar Evereste was followed using the SSR marker ChFbE06 that co-segregates with Fb_E, with the PCR conditions as described previously (Parravicini et al 2011). This SSR marker in Evereste amplifies an allele of 273 bp in coupling with fire blight resistance that is specific to the donor Evereste (private allele) and an allele of 256 bp that is common to Evereste and other cultivars (i.e.…”

“…Total BC 0 1 2 4 2 7 2 5 c 14 90 a Presence of the BpMADS4 transgene (on linkage group 4, Flachowsky et al 2011) in each seedling was assessed by using the specific primers BpMADS4_F and BpMADS4_R as described by Flachowsky et al (2007) b The SSR marker ChFbE06 co-segregates with the fire blight resistance locus Fb_E from Evereste in more than 2,700 plants tested (on linkage group 12, Durel et al 2009); the length of the resistant allele is 273 bp (Parravicini et al 2011) c All BC 0 1 seedlings carrying the BpMADS4 transgene and the resistant allele of SSR marker ChFbE06 were selected for subsequent background selection, except one seedling from the cross E 9 T_5 9 Milwa (strain CFBP 1430 at 3 9 10 8 cfu/mL) and a single scoring date of the percent lesion length 21 days after inoculation (PLL 21 DAI). Significant pairwise differences of PLL 21 DAI within the genotype groups and between the genotype groups and the controls were investigated by the Mann-Whitney U test (significance level 0.05) using the software SPSS Statistics 19 (IBM, Germany).…”

“…The genetic basis of its resistance to E. amylovora was recently deciphered through the identification of a major quantitative trait locus (QTL) located on linkage group (LG) 12, named Fb_E, explaining from 50 to 70% of the phenotypic variation in a MM106 9 Evereste F1 progeny (Durel et al 2009). At the onset of our study, the QTL region was being encompassed with molecular markers (Parravicini Rusca 2010) and SSR markers co-segregating with the resistance locus Fb_E were being developed (Parravicini et al 2011). For these reasons, as well as the high level of fire blight resistance that can be obtained with the locus Fb_E, this resistance appeared to us as a prime candidate for markerassisted introgression into a domestic apple genetic background.…”

“…For these reasons, as well as the high level of fire blight resistance that can be obtained with the locus Fb_E, this resistance appeared to us as a prime candidate for markerassisted introgression into a domestic apple genetic background. In this study, we describe the use of the transgenic line T1190 to accelerate the markerassisted introgression of the fire blight resistance locus Fb_E from the ornamental apple Evereste (Durel et al 2009;Parravicini et al 2011) over two breeding generations (F1 and BC 0 1). We also report on the selection of BC 0 1 seedlings for the lowest possible genomic contribution from Evereste using a set of simple sequence repeat (SSR) markers spanning the apple genome.…”

Molecular response of resistant and susceptible apple genotypes to Erwinia amylovora infection

“…Recently, nucleotide-binding site -leucine-rich repeat (NBS-LRR) gene has been mapped to fire blight-resistance linkage groups in wild species Malus × robusta (Fahrentrapp et al 2013) and in ornamental apple Malus × domestica cv. Evereste (Parravicini et al 2011). The product of this gene is known to interact with AvrRpt2EA effector of E. amylovora and potentially play a role in plant defence reaction.…”