L'organogènese inflorescentielle dans les bourgeons anticipés de vigne (Vitis vinifera L. cépage Pinot)

Organogenesis of inflorescences in the lateral buds of grapevine (Vitis vinifera L. cv. Pinot)The formation of inflorescences in lateral buds has been investigated by studies of longitudinal sections of paraffin-embedded lateral buds. The lateral buds at position 6 (from the base) were collected from non-decapitated shoots, from the middle of May to the end of June. The different developmental stages of inflorescence and also a chronological analysis have been described. The observations inform about the organogenetic ch aracteristics which occur in the absence of decapitation of the main shoot

Recovery of mutants impaired in pathogenicity after transposition of Impala in Fusarium oxysporum f. sp. melonis

The ability of transposon impala to inactivate genes involved in pathogenicity was tested in Fusarium oxysporum f. sp. melonis. Somatic excision of an impala copy inserted in the nitrate reductase-encoding niaD gene was positively selected through a phenotypic assay based on the restoration of nitrate reductase activity. Independent excision events were analyzed molecularly and shown to carry reinsertedimpala in more than 70% of the cases. Mapping of reinserted impala elements on large NotI-restriction fragments showed that impala transposes randomly. By screening 746 revertants on plants, a high proportion (3.5%) of mutants impaired in their pathogenic potential was recovered. According to the kinetics of wilt symptom development, the strains that were impaired in pathogenicity were clustered in three classes: class 1 grouped two strains that never induced Fusarium wilt symptoms on the host plant; class 2 and class 3 grouped 15 and 9 revertants which caused symptoms more than 50 and 30 days after inoculation, respectively. The first results demonstrate the efficiency of transposition in generating mutants affected in pathogenicity, which are usually difficult to obtain by classical mutagenesis, and open the possibility to clone the altered genes with impala as a tag

The Nuclear Protein Sge1 of Fusarium oxysporum Is Required for Parasitic Growth

Dimorphism or morphogenic conversion is exploited by several pathogenic fungi and is required for tissue invasion and/or survival in the host. We have identified a homolog of a master regulator of this morphological switch in the plant pathogenic fungus Fusarium oxysporum f. sp. lycopersici. This non-dimorphic fungus causes vascular wilt disease in tomato by penetrating the plant roots and colonizing the vascular tissue. Gene knock-out and complementation studies established that the gene for this putative regulator, SGE1 (SIX Gene Expression 1), is essential for pathogenicity. In addition, microscopic analysis using fluorescent proteins revealed that Sge1 is localized in the nucleus, is not required for root colonization and penetration, but is required for parasitic growth. Furthermore, Sge1 is required for expression of genes encoding effectors that are secreted during infection. We propose that Sge1 is required in F. oxysporum and other non-dimorphic (plant) pathogenic fungi for parasitic growth

Modes of action of non-pathogenic strains of Fusarium oxysporum in controlling fusarium wilts

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Process of tomato root colonization by a pathogenic strain of Fusarium oxysporum f. sp. lycopersici in comparison with a non-pathogenic strain

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Colonization of tomato root by a non-pathogenic strain of Fusarium oxysporum

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Potentialités de croissance et de fertilité du bourgeon latent chez la vigne (<em>Vitis vinifera</em> L.), étude réalisée de l'initiation à l'entrée en dormance

Les potentialites de croissance et de fertilité du bourgeon latent de rang 6 (Vitis vinifera L, cépage Pinot noir) sont étudiées grâce à des techniques de forçage pratiquées au vignoble. Ces techniques sont appliquées au bourgeon latent depuis l'état méristématique jusqu'à son entrée en dormance. Les potentialités de croissance importantes diminuent en même temps que la dormance s'installe. Nous avons montré qu'il est possible d'obtenir une certaine fertilité à partir de bourgeons qui n'ont pas encore formé d'inflorescences au moment des forçages. Lorsque les inflorescences sont préformées dans les bourgeons, la fertilité augmente avec le nombre et l'état de différenciation de celles-ci. +++ The potentialities of the dormant buds at position 6 (Vitis vinifera L. cv Pinot noir) concerning growth and fertility have been investigated with forcing techniques executed in the vineyard. These techniques have been performed on the dormant buds since the meristematic state to the beginning of dormancy. The important growth potentialities decrease when the dormancy begins. We demonstrated that it is possible to obtain some fertility from buds which have not formed inflorescences at the time of forcing. When the inflorescences are formed in the buds the fertility increases with the number and the differenciation of these

Modes of action of non-pathogenic strains of Fusarium oxysporum in controlling fusarium wilts

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Fertilité des rameaux anticipés de vigne (Vitis vinifera L.) : II. — Influence de la fertilité potentielle et de la vitesse de croissance

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