Spatial Genetic Structure and Pathogenic Race Composition at the Field Scale in the Sunflower Downy Mildew Pathogen, Plasmopara halstedii

Yield losses in sunflower crops caused by Plasmopara halstedii can be up to 100%, depending on the cultivar susceptibility, environmental conditions, and virulence of the pathogen population. The aim of this study was to investigate the genetic and phenotypic structure of a sunflower downy mildew agent at the field scale. The genetic diversity of 250 P. halstedii isolates collected from one field in southern France was assessed using single-nucleotide polymorphisms (SNPs) and single sequence repeats (SSR). A total of 109 multilocus genotypes (MLG) were identified among the 250 isolates collected in the field. Four genotypes were repeated more than 20 times and spatially spread over the field. Estimates of genetic relationships among P. halstedii isolates using principal component analysis and a Bayesian clustering approach demonstrated that the isolates are grouped into two main genetic clusters. A high level of genetic differentiation among clusters was detected (FST = 0.35), indicating overall limited exchange between them, but our results also suggest that recombination between individuals of these groups is not rare. Genetic clusters were highly related to pathotypes, as previously described for this pathogen species. Eight different races were identified (100, 300, 304, 307, 703, 704, 707, and 714), with race 304 being predominant and present at most of the sites. The co-existence of multiple races at the field level is a new finding that could have important implications for the management of sunflower downy mildew. These data provide the first population-wide picture of the genetic structure of P. halstedii at a fine spatial scale.publishedVersio

Comparative genetic analysis of quantitative traits in sunflower (Helianthus annuus L.)

One hundred and fifty F2–F3 families from a cross between two inbred sunflower lines FU and PAZ2 were used to map quantitative trait loci (QTL) for resistance to white rot (Sclerotinia sclerotiorum) attacks of terminal buds and capitula, and black stem (Phoma macdonaldii). A genetic linkage map of 18 linkage groups with 216 molecular markers spanning 1,937 cM was constructed. Disease resistances were measured in field experiments for S. sclerotiorum and under controlled conditions for P. macdonaldii. For resistance to S. sclerotiorum terminal bud attack, seven QTL were identified, each explaining less than 10% of phenotypic variance. For capitulum attack by this parasite, there were four QTL (each explaining up to 20% of variation) and for P. macdonaldii resistance, four QTL were identified, each having effects of up to 16%. The S. sclerotiorum capitulum resistance QTL were compared with those reported previously and it was concluded that resistance to this disease is governed by a considerable number of QTL, located on almost all the sunflower linkage groups

Mildiou du tournesol : des races de plus en plus nombreuses

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Pénétration de Rosellinia necatrix (Hart.) Berl. dans les racines du pommier en conditions de contamination artificielle

National audienceRosellinia necatrix (Hart.) Berl. is an ascomycete causing white root rot of certain ornamental species and fruit crops. This article describes the penetration of apple roots by R. necatrix. Inoculation of young plants grown under axenic conditions in pots in a mist chamber showed that infection occurs in four phases, each involving differents forms of aggregate organs of the pathogen : 1) external proliferation in the form of a mycelial thallus or strings made up of undifferentiated cells ; 2) formation of a « penetration sclerotium », consisting of a melanized cortex of pseudoparenchyma and a white medulla of prosenchyma ; 3) penetration of host tissues by mycelium developing from the medulla ; 4) internal proliferation in the form of subcortical strings of prosenchyma. The morphogenetic plasticity of the fungus and its pathogenicity factors are discussed.Rosellinia necatrix (Hart.) Berl. est un champignon ascomycète, agent du « pourridié laineux » de certaines plantes ornementales et cultures fruitières. Cet article est consacré à une description de la pénétration de R. necatrix dans les racines du pommier. Les inoculations de jeunes plants cultivés en axénie, en pots et en caissons à brouillard, ont montré que l’infection se déroule en quatre phases faisant intervenir de la part du champignon pathogène des organes agrégés bien différents : - prolifération externe sous la forme de toiles mycéliennes ou de cordons formés d’articles indifférenciés ; - formation d’un « sclérote de pénétration » constitué d’un cortex mélanisé à structure pseudoparenchymateuse et d’une medulla blanche à structure prosenchymateuse ; - pénétration dans les tissus de l’hôte effectuée par le mycélium de la medulla ; - prolifération interne sous la forme de cordons subcorticalis à structure prosenchymateuse. La discussion porte sur la plasticité morphogénétique du champignon et sur les déterminants du pouvoir pathogène

Alteração da dimensão vertical da oclusão e sua relação com a disfunção temporomandibular

A etiologia das disfunções temporomandibulares é controversa e resulta de uma combinação de factores de risco, incluindo factores ambientais, traumáticos, comportamentais, psicológicos e oclusais. Vários autores alegaram que uma alteração na dimensão vertical da oclusão pode afetar a função, o conforto e a estética do paciente (Goiato et al., 2013). A etiologia de uma alteração da dimensão vertical da oclusão é múltipla, e muitas investigações científicas nesta área propõem várias técnicas para determinar a dimensão vertical da oclusão, mas nenhuma parece destacar-se quanto à fiabilidade e precisão. O objetivo deste trabalho é discutir a correlação entre a alteração da dimensão vertical da oclusão e as disfunções temporomandibulares. De um total de 313 artigos relacionados com este tópico e encontrados através do PubMed e Google Scholar, foram selecionados 62 artigos para uma leitura completa, incluindo 18 estudos sobre a relação entre dimensão vertical da oclusão e as disfunções temporomandibulares. Destes, 11 estudos mostraram uma correlação positiva entre elas e nos restantes 7 estudos nenhuma associação é relatada.The etiology of temporomandibular disorders is controversial and results from a combination of risk factors, including environmental, traumatic, behavioural, psychological and occlusive factors. Several authors have argued that an alteration in the vertical dimension of occlusion can affect the patient's function, comfort and aesthetics (Goiato et al., 2013). The etiology of a change in the vertical dimension of the occlusion is multiple, and many scientific investigations in this area propose various techniques for measuring vertical dimension of occlusion, but none seems more accurate or reliable than another. The aim of this work is to discuss the correlation between vertical dimension of occlusion change and temporomandibular disorders. From a total of 313 articles related to this topic and found through PubMed and Google Scholar, 62 articles were selected for a complete reading, including 18 studies on the relationship between vertical dimension of occlusion and temporomandibular disorders. 11 studies found a positive correlation between them , while in the remaining 7 studies no association is reported

Pénétration de Rosellinia necatrix (Hart.) Berl. dans les racines du pommier en conditions de contamination artificielle

Rosellinia necatrix (Hart.) Berl. est un champignon ascomycète, agent du « pourridié laineux » de certaines plantes ornementales et cultures fruitières. Cet article est consacré à une description de la pénétration de R. necatrix dans les racines du pommier. Les inoculations de jeunes plants cultivés en axénie, en pots et en caissons à brouillard, ont montré que l'infection se déroule en quatre phases faisant intervenir de la part du champignon pathogène des organes agrégés bien différents : - prolifération externe sous la forme de toiles mycéliennes ou de cordons formés d'articles indifférenciés ; - formation d'un « sclérote de pénétration » constitué d'un cortex mélanisé à structure pseudoparenchymateuse et d'une medulla blanche à structure prosenchymateuse ; - pénétration dans les tissus de l'hôte effectuée par le mycélium de la medulla ; - prolifération interne sous la forme de cordons subcorticalis à structure prosenchymateuse. La discussion porte sur la plasticité morphogénétique du champignon et sur les déterminants du pouvoir pathogène

Etude sur les toxines produites par Rosellinia necatrix (Hart.) Berl.

L'étude du comportement d'organes excisés des hôtes cultivés en France vis-à-vis des toxines produites par le champignon in vitro et in vivo montre que la spécificité d'action de ces dernières ne correspond pas à celle du champignon. Cependant, sur les pommiers, on observe une correspondance entre la sensibilité des génotypes de l'hôte au pathogène et aux toxines ; il apparaît également une certaine relation entre le pouvoir pathogène des différents isolats et leur aptitude à produire des toxines in vitro. La discussion porte sur les déterminants du pouvoir pathogène de R. necatrix

Etude sur les toxines produites par Rosellinia necatrix (Hart.) Berl.

L'étude du comportement d'organes excisés des hôtes cultivés en France vis-à-vis des toxines produites par le champignon in vitro et in vivo montre que la spécificité d'action de ces dernières ne correspond pas à celle du champignon. Cependant, sur les pommiers, on observe une correspondance entre la sensibilité des génotypes de l'hôte au pathogène et aux toxines ; il apparaît également une certaine relation entre le pouvoir pathogène des différents isolats et leur aptitude à produire des toxines in vitro. La discussion porte sur les déterminants du pouvoir pathogène de R. necatrix