A new pear scab resistance gene Rvp1 from the European pear cultivar ‘Navara’ maps in a genomic region syntenic to an apple scab resistance gene cluster on linkage group 2

Scab, caused by the ascomycete fungus Venturia pirina, leads to severe damage on European pear varieties resulting in a loss of commercial value and requiring frequent use of fungicides. Identifying scab resistance genes, developing molecular markers linked to these genes and establishing marker-assisted selection would be an effective way to improve European pear breeding for scab resistance. Most of the European pear cultivars (Pyrus communis) are currently reported to be sensitive. The pear cultivar ‘Navara’ was shown to carry a major scab resistance gene whose phenotypic expression in seedling progenies was a typical stellate necrosis symptom. The resistance gene was called Rvp1, for resistance to V. pirina, and was mapped on linkage group 2 of the pear genome close to microsatellite marker CH02b10. This genomic region is known to carry a cluster of scab resistance genes in apple indicating a first functional synteny for scab resistance between apple and pear

Differential selection pressures exerted by host resistance quantitative trait loci on a pathogen population: a case study in an apple × Venturia inaequalis pathosystem

Understanding how pathogens evolve according to pressures exerted by their plant hosts is essential for the derivation of strategies aimed at the durable management of resistant cultivars. The spectrum of action of the resistance factors in the partially resistant cultivars is thought to be an important determinant of resistance durability. However, it has not yet been demonstrated whether the pressures exerted by quantitative resistance are different according to their spectrum of action.To investigate selection pressures exerted by apple genotypes harbouring various resistance quantitative trait loci (QTLs) on a mixed inoculum of the scab disease agent, Venturia inaequalis, we monitored V. inaequalis isolate proportions on diseased apple leaves of an F1 progeny using quantitative pyrosequencing technology and QTL mapping. Broad-spectrum resistances did not exert any differential selection pressures on the mixed inoculum, whereas narrow-spectrum resistances decreased the frequencies of some isolates in the mixture relative to the susceptible host genotypes. Our results suggest that the management of resistant cultivars should be different according to the spectrum of action of their resistance factors. The pyramiding of broad-spectrum factors or the use of a mixture of apple genotypes that carry narrow-spectrum resistance factors are two possible strategies for the minimization of resistance erosion

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’

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

Efficacy of Continuous Interleukin 1 Blockade in Mevalonate Kinase Deficiency: A Multicenter Retrospective Study in 13 Adult Patients and Literature Review

OBJECTIVE: To report efficacy and tolerance of interleukin 1 blockade in adult patients with mevalonate kinase deficiency (MKD). METHODS: We retrospectively collected data on 13 patients with MKD who had received anakinra (n = 10) and canakinumab (n = 7). RESULTS: Anakinra resulted in complete or partial remission in 3/10 and 5/10 patients, respectively, and no efficacy in 2/10, but a switch to canakinumab led to partial remission. Canakinumab resulted in complete or partial remission in 3/7 and 4/7 patients, respectively. CONCLUSION: These data support frequent partial responses, showing a better response with canakinumab. The genotype and therapeutic outcomes correlation should help in the personalization of treatment

Virulence characterization of Venturia inaequalis reference isolates on the differential set of Malus hosts

A set of differential hosts has recently been identified for 17 apple scab resistance genes in an updated system for defining gene-for-gene (GfG) relationships in the Venturia inaequalis-Malus pathosystem. However, a set of reference isolates characterized for their complementary avirulence alleles is not yet available. In this paper, we report on improving the set of differential hosts for h(7) and propose the apple genotype LPG3-29 as carrying the single major resistance gene Rvi7. We characterized a reference set of 23 V. inaequalis isolates on 14 differential apple hosts carrying major resistance genes under controlled conditions. We identified isolates that were virulent on at least one of the following defined resistance gene hosts: h(1), h(2), h(3), h(4), h(5), h(6), h(7), h(8), h(9), h(10) and h(13). Sixteen different virulence patterns were observed. In general, the isolates carried one to three virulences, but some of them were more complex, with up to six virulences. This set of well-characterized isolates will be helpful for the identification of additional apple scab resistance genes in apple germplasm and the characterization of new GfG relationships to help improve our understanding of the host-pathogen interactions in the V. inaequalis-Malus pathosystem