Contribution à l'étude de la variabilité biologique du virus de la sharka. Amélioration de sa détection par le test Elisa (enzyme-linked immunosorbent assay)

* INRA, Station de Pathologie végétale, Domaine St Maurice, 84140 Montfavet (FRA) Diffusion du document : INRA, Station de Pathologie végétale, Domaine St Maurice, 84140 Montfavet (FRA) Diplôme : Dr. d'UniversitéNDN

Etude comparée de différentes méthodes de détection du virus de la sharka (plum pox virus)

* INRA, Station de Pathologie végétale, Domaine St Maurice, 84140 Montfavet cedex Diffusion du document : INRA, Station de Pathologie végétale, Domaine St Maurice, 84140 Montfavet cedex Diplôme : DE

Development of resistance to pyrrolnitrin and associated fitness costs in the plant pathogen Botrytis cinerea

International audienc

Comparison of the development in planta of a pyrrolnitrin-resistant mutant of Botrytis cinerea and its sensitive wild-type parent isolate

International audienceBotrytis cinerea is able to build-up resistance to pyrrolnitrin, an antibiotic produced by diverse biocontrol agents, possibly compromising the durability of this method of disease control. The development of two near-isogenic lines of B. cinerea differing in their level of resistance to pyrrolnitrin was compared in tomato plants and on PDA medium. In tomato plants, significant differences in the percentage of infected petioles 1 day after inoculation and in symptom progression on petioles and stems were observed between the resistant mutant and the sensitive wild-type parent, suggesting a difference in their level of aggressiveness. Cytohistological investigations revealed that conidia of both near-isogenic lines germinated 6 h after inoculation and mycelium developed within petiole tissues 12 h after inoculation. However, while the wild-type parent isolate spread throughout the petiole and rapidly invaded the stem tissues via the leaf-abscission zone 72 h after inoculation, the pyrrolnitrin-resistant mutant failed to extend beyond petiole tissues to invade the stem. Moreover, 72 h after inoculation, the mycelial development of the pyrrolnitrin-resistant mutant was accompanied by abnormal glycogen accumulation and chlamydospore-like cell formation. In contrast, wild-type parent mycelium was normally structured with intensive colonization of stem tissues. Additionally, on PDA medium the mycelium of the pyrrolnitrin-resistant mutant was less vigorous than the wild-type isolate. These results suggest that the acquisition of pyrrolnitrin-resistance in B. cinerea is accompanied by changes in mycelial structure and reduction in mycelial growth, leading to a noticeable loss of aggressiveness on tomato plants

Unraveling the infection process of garlic by Fusarium proliferatum, the causal agent of root rot

International audienceSince the mid-2000s, and despite demanding production rules, Fusarium proliferatum (Matsushima) Niremberg has been found on garlic heads during storage inducing root and bulbs rots. Brown spots on the surface of garlic cloves and water-soaking of heads were noted. Histological observations of the fungus during early stages of infection were made from clove to the cellular levels. Fusarium proliferatum germinates, colonizes roots and degrades the outer root and parechchyma cell layers 72 h post inoculation. Conidium germination and host colonization are facilitated by the emergence of garlic roots, creating cellular debris and natural wounds. Hyphae of the pathogen did not penetrate healthy host cells and appeared to degrade them before penetration. These results provide understanding of when and how quickly F. prolife-ratum penetrates garlic bulbs. This is a primary step towards elucidating the life cycle of this pathogen during the garlic drying process, and development of an efficient and sustainable bulb rot management strategy

Impact of soaking process on the microstructure of cowpea seeds in relation to solid losses and water absorption

International audienc

Characterization of the developmental stages of cypress zygotic embryos by two-dimensional electrophoresis and by cytochemistry

International audienc

Host-parasite interactions from the inside: Plant reproductive ontogeny drives specialization in parasitic insects

Host plant interactions are likely key drivers of evolutionary processes involved in the diversification of phytophagous insects. Granivory has received substantial attention for its crucial role in shaping the interaction between plants and their seed parasites, but fine-scale mechanisms explaining the role of host plant reproductive biology on specialization of seed parasites remain poorly described. In a comparative approach using plant histological techniques, we tested the hypotheses that different seed parasite species synchronize their life cycles to specific stages in seed development, and that the stage they target depends on major differences in seed development programs. In a pinaceous system, seed storage products are initiated before ovule fertilization and the wasps target the ovule’s nucellus during megagametogenesis, a stage at which larvae may benefit from the by-products derived from both secreting cells and dying nucellar cells. In a cupressaceous system, oviposition activity peaks later, during embryogenesis, and the wasps target the ovule’s megagametophyte where larvae may benefit from cell disintegration during embryogenesis. Our cytohistological approach shows for the first time how, despite divergent oviposition targets, different parasite species share a common strategy that consists of first competing for nutrients with developing plant structures, and then consuming these developed structures to complete their development. Our results support the prediction that seed developmental program is an axis for specialization in seed parasites, and that it could be an important parameter in models of their ecological and taxonomic divergence. This study provides the basis for further investigating the possibility of the link between plant ontogeny and pre-dispersal seed parasitis

Comparison of the ontogeny of <i>Cupressus sempervirens</i> female reproductive structures with seasonal timing of the oviposition activity of the seed wasp <i>Megastigmus wachtli</i> (MW) in southeastern France.

<p><b>a</b>, Longitudinal section of an ovule collected on June 22, 2011 showing a megagametophyte at prefertilization stage with archegonial complex (star). Note the presence of pollen tubes within the nucellus. <b>b</b>, Post-fertilisation megagametophyte from an ovule collected on July 10, 2011. The early proembryo (arrow) is just emerging from the fertilized archegonium. <b>c</b>, and <b>d</b>, Sections from ovules collected on July 27 and August 24, 2011, respectively showing proembryos (arrows) within the megagametophyte tissues. CC, corrosion cavity; M, megagametophyte; N, nucellus; PT, pollen tubes. All scale bars 200 = μm. <b>e</b>, Frequencies of oviposition activity in MW; oviposition begins at female emergence. Grey bars: periods of maximal oviposition activity. <b>f</b>, Section of a parasitized <i>C</i>. <i>sempervirens</i> young seed collected on July 22, 2011 and showing a larva (arrow) within the megagametophyte tissue. M, megagametophyte; N, nucellus. Bar 200 = μm.</p