Inheritance of red leaf colour from pear red sports of 'Doyenné du Comice', 'Bartlett' and 'Beurré Hardy'

International audienceThe pear breeding programme at INRA Angers-Beaucouze is partly devoted to screen for red skin colour from mutants derived from European pear cultivars. These mutants were selected around 1950 in the USA from 'Doyenne du Comice', 'Williams' and 'Beurre Hardy'. Several combinations involving these red mutants and also cultivars including 'Lombacad' and 'Red Satin' were studied for the inheritance of red colour in the leaves after scoring in the greenhouse. In the field, vigour and tree habit of the seedlings were appreciated and compared to the green seedlings. The hypothesis of a genotype C/c for red leaves is confirmed for 'Red Comice' and 'Royal Red Hardy' as in 'Max Red Bartlett'. Three classes of architecture: standard-spread, erect, and compact, were clearly distinguished according to the genotype at the locus C. The red flesh character of the fruit is also under investigation and the red colour of the hypocotyl is proposed as an early putative marker for this trait

Stratégies for fire blight resistance breeding in pear (Pyrus communis); 30 years of experience

International audienceA pear breeding programme was developed at INRA Angers-Beaucouze from the 1960s and is still in progress. In the 1960s, the programme put emphasis on late maturing fruit with a long storage ability; from the 1980s, the programme was mostly devoted to fire blight resistance. A large amount of crosses and seedlings were scored along the years, giving rise to pear selections which were trialled for a future release. The seedlings from the first set (1960s) were grown without any greenhouse selection and only screened in the field for traditional quality traits. The seedlings from the other set (1980s) were grown after selection in the greenhouse for fire blight low susceptibility, and then transferred in the field for screening on the same traditional quality traits. The resultant selections from the 2 sets of crosses were grafted and scored in the greenhouse for fire blight resistance along a period of 30 years. It appears that the process of selection in the greenhouse is not leading to promising pear selections with a very good score for fire blight resistance. These results are discussed for proposing a strategy which will be efficient for screening new cultivars with a better score for fire blight resistance

Available water capacity from a multidisciplinary and multiscale viewpoint. A review

International audienceSoil–plant–atmosphere models and certain land surface models usually require information about the ability of soils to store and release water. Thus, a critical soil parameter for such reservoir-like models is the available water capacity (AWC), which is usually recognized as the most influential parameter when modeling water transfer. AWC does not have a single definition despite its wide use by scientists in research models, by regional managers as land-management tools and by farmers as decision-aid tools. Methods used to estimate AWC are also diverse, including laboratory measurements of soil samples, field monitoring, use of pedotransfer functions, and inverse modeling of soil-vegetation models. However, the resulting estimates differ and, depending on the method and scale, may have high uncertainty. Here, we review the many definitions of AWC, as well as soil and soil–plant approaches used to estimate it from local to larger spatial scales. We focus especially on the limits and uncertainties of each method. We demonstrate that in soil science, AWC represents a capacity—the size of the water reservoir that plants can use—whereas in agronomy, it represents an ability—the quantity of water that a plant can withdraw from the soil. We claim that the two approaches should be hybridized to improve the definitions and estimates of AWC. We also recommend future directions: (i) adapt pedotransfer functions to provide information about plants, (ii) integrate newly available information from soil mapping in spatial inverse-modeling applications, and (iii) integrate model-inversion results into methods for digital soil mapping

Pear breeding for Scab and Psylla resistance

2 vol.Pear breeding for Scab and Psylla resistance. Xth International Symposium on Pear Growin

Genome mapping of postzygotic hybrid necrosis in an interspecific pear population

International audienceDeleterious epistatic interactions in plant inter- and intraspecific hybrids can cause a phenomenon known as hybrid necrosis, characterized by a typical seedling phenotype whose main distinguishing features are dwarfism, tissue necrosis and in some cases lethality. Identification of the chromosome regions associated with this type of incompatibility is important not only to increase our understanding of the evolutionary diversification that led to speciation but also for breeding purposes. Development of molecular markers linked to the lethal genes will allow breeders to avoid incompatible inbred combinations that could affect the expression of important agronomic tratis co-segregating with these genes. Although hybrid necrosis has been reported in several plant taxa, including Rosaceae species, this phenomenon has not been described previously in pear. In the interspecific pear population resulting from a cross between PEAR3 (Pyrus bretschneideri × Pyrus communis) and ‘Moonglow’ (P. communis), we observed two types of hybrid necrosis, expressed at different stages of plant development. Using a combination of previously mapped and newly developed genetic markers, we identified three chromosome regions associated with these two types of lethality, which were genetically independent. One type resulted from a negative epistatic interaction between a locus on linkage group 5 (LG5) of PEAR3 and a locus on LG1 of ‘Moonglow’, while the second type was due to a gene that maps to LG2 of PEAR3 and which either acts alone or more probably interacts with another gene of unknown location inherited from ‘Moonglow’

Potentiating tangle formation reduces acute toxicity of soluble tau species in the rat

International audienceTauopathies are neurodegenerative diseases characterized by the aggregation of tau protein. These pathologies exhibit a wide variety of clinical and anatomo-pathological presentations, which may result from different pathological mechanisms. Although tau inclusions are a common feature in all these diseases, recent evidence instead implicates small oligomeric aggregates as drivers of tau-induced toxicity. Hence $in\ vivo$ model systems displaying either soluble or fibrillary forms of wild-type or mutant tau are needed to better identify their respective pathological pathways. Here we used adeno-associated viruses to mediate gene transfer of human tau to the rat brain to develop models of pure tauopathies. Two different constructs were used, each giving rise to a specific phenotype developing in less than 3 months. First, hTAU$^{WT}$ overexpression led to a strong hyperphosphorylation of the protein, which was associated with neurotoxicity in the absence of any significant aggregation. In sharp contrast, its co-expression with the pro-aggregation peptide TauRD-$\Delta$K280 in the hTAU$^{ProAggr}$group strongly promoted its aggregation into Gallyas-positive neurofibrillary tangles, while preserving neuronal survival. Our results support the hypothesis that soluble tau species are key players of tau-induced neurodegeneration

Neuronal tau species transfer to astrocytes and induce their loss according to tau aggregation state

International audienceDeposits of different abnormal forms of tau in neurons and astrocytes represent key anatomo-pathological features of tauopathies. Although tau protein is highly enriched in neurons and poorly expressed by astrocytes, the origin of astrocytic tau is still elusive. Here, we used innovative gene transfer tools to model tauopathies in adult mouse brains and to investigate the origin of astrocytic tau. We showed in our adeno-associated virus (AAV)-based models and in Thy-Tau22 transgenic mice that astrocytic tau pathology can emerge secondarily to neuronal pathology. By designing an in vivo reporter system, we further demonstrated bidirectional exchanges of tau species between neurons and astrocytes. We then determined the consequences of tau accumulation in astrocytes on their survival in models displaying various status of tau aggregation. Using stereological counting of astrocytes, we report that, as for neurons, soluble tau species are highly toxic to some subpopulations of astrocytes in the hippocampus, whereas the accumulation of tau aggregates does not affect their survival. Thus, astrocytes are not mere bystanders of neuronal pathology. Our results strongly suggest that tau pathology in astrocytes may significantly contribute to clinical symptoms

Pseudo-chromosome–length genome assembly of a double haploid “Bartlett” pear (Pyrus communis L.)

Background: We report an improved assembly and scaffolding of the European pear (Pyrus communis L.) genome (referred to as BartlettDHv2.0), obtained using a combination of Pacific Biosciences RSII long-read sequencing, Bionano optical mapping, chromatin interaction capture (Hi-C), and genetic mapping. The sample selected for sequencing is a double haploid derived from the same "Bartlett" reference pear that was previously sequenced. Sequencing of di-haploid plants makes assembly more tractable in highly heterozygous species such as P. communis. Findings: A total of 496.9 Mb corresponding to 97% of the estimated genome size were assembled into 494 scaffolds. Hi-C data and a high-density genetic map allowed us to anchor and orient 87% of the sequence on the 17 pear chromosomes. Approximately 50% (247 Mb) of the genome consists of repetitive sequences. Gene annotation confirmed the presence of 37,445 protein-coding genes, which is 13% fewer than previously predicted. Conclusions: We showed that the use of a doubled-haploid plant is an effective solution to the problems presented by high levels of heterozygosity and duplication for the generation of high-quality genome assemblies. We present a high-quality chromosome-scale assembly of the European pear Pyrus communis and demostrate its high degree of synteny with the genomes of Malus x Domestica and Pyrus x bretschneideri