Downy mildew: is resistance linked to inoculum concentration?

Leaves of different Vitis vinifera cultivars, susceptible (‘Chasselas’ and ‘2185’), less susceptible (‘2142’) or resistant to downy mildew ('Solaris’ and ‘2091’), were inoculated with four different concentrations of an aqueous sporangia suspension of Plasmopara viticola (5 × 105, 2 × 105, 6 × 104 and 2 × 104 sporangia·ml-1). The infection rate of these samples was then examined by light microscopy and synthesis of stilbenes was analysed at infection sites. Infection rate increased parallel with inoculum concentration, but there was no correlation between the infection rate and resistance to P. viticola. Moreover, at the lowest inoculum concentration, the infection rate is similar for susceptible and resistant grapevine varieties. Quantification of stilbenes at 72 hpi showed that at the lowest inoculum concentration, the most susceptible grape variety synthesized the largest amount of stilbenes, whose level remained however below the ED50 values defined for each of them. Conversely, at the highest inoculum concentration, the most resistant varieties produced the highest amounts of the most toxic stilbenes against P. viticola. The critical role of the inoculum concentration used for artificial inoculation to evaluate grapevine resistance to downy mildew is discussed.

Leaf morphological characteristics and stilbene production differently affect downy mildew resistance of Vitis vinifera varieties grown in Italy

The degree of resistance to downy mildew of grape varieties belonging to the oenological tradition of Central Italy was evaluated by the analysis of plant responses to pathogen infections carried out in natural and controlled environments. Leaf morphological traits, such as hair and stomatal density, were determined for each variety, and the percentage of infected stomata and pathogen colonization of host mesophyll at 24, 48, and 72 hours post inoculation were assessed by epifluorescence microscopy. Furthermore, stilbene production at the site of Plasmopara viticola infection was analyzed at 72 hours post inoculation. Results indicate differences in resistance to downy mildew among selected varieties. Different significant values were detected among grapevines in the percentage of infected stomata and average number of successfully penetrated zoospores per stomata and per leaf surface unit. Differences also emerged in the rate of pathogen growth and stilbene production, signifying that defence mechanisms involved or induced during pathogen infection could be differentially effective among grapevine cultivars in limiting disease progression.

La caracterización molecular y ampelográfica de clones de "Albariño", "Savagnin Blanc" y "Caíño Blanco" (Vitis vinifera L.) demuestra que son cultivares diferentes

The grapevine cultivar "Albariño" is one of the oldest grown in the vine-growing areas of North-Western Spain and Northern Portugal. Since recognition of Origin Denomination status for the Rías Baixas region (the coast of Western Galicia, Spain) in 1987, the economic importance of this cultivar has increased, and its grapes are now among the most expensive in Spain. The area occupied by "Albariño" vines in this region is increasing every year, and the wines made from its grapes are gaining international recognition. These events, plus the fact that "Albariño" was little known outside its traditional growing area, have led to speculation about its origin and the existence of synonyms. Misnames of "Albariño" have included "Savagnin Blanc" and "Caíño Blanco". The present work compares "Albariño", "Savagnin Blanc" and "Caíño Blanco" ampelographically (i.e., it compares shoot, leaf, grape cluster, berry and seed characteristics) and molecularly using microsatellite markers. The results show that they are in fact three different cultivars providing a complete description. For "Caíño Blanco", there is little previously reported information.El "Albariño" es uno de los cultivares más antiguos de la zona vitícola del Noroeste de España y norte de Portugal. Desde la aprobación en el año 1987 de la Denominación de Origen Rías Baixas, este cultivar es el de mayor valor económico de esta zona vitícola, y su uva alcanza uno de los precios más elevados de España. Su superficie de cultivo, dentro de esta Denominación de Origen, se multiplica año tras año, y sus vinos adquieren fama internacional. Todo ello, unido a que era un cultivar poco conocido fuera de esta pequeña zona vitícola española, ha llevado a la aparición en los últimos años de diversas especulaciones sobre su origen, y a la atribución de diferentes sinonimias. Entre los nombres erróneamente atribuidos al "Albariño" se encuentran "Savagnin Blanc" y "Caíño Blanco". En el presente trabajo se hace un estudio comparativo de los tres cultivares a nivel ampelográfico (brote, hoja, racimo, baya, semilla) y a nivel molecular por medio de marcadores microsatélite. Los resultados demuestran que "Albariño", "Savagnin Blanc" y "Caíño Blanco" son cultivares distintos, proporcionando una completa descripción de cada uno. De uno de ellos, "Caíño Blanco", existe muy poca información previa

Variability of the stomata among 'Albariño' (Vitis vinifera L.) clones and its relationship with susceptibility to downy mildew

Research Note

Macro- and microscopic leaf characteristics of six grapevine genotypes (Vitis spp.) with different susceptibilities to grapevine downy mildew

This work reports the leaf morphology of six grapevine genotypes, five belonging to Vitis vinifera and one to Vitis riparia. Earlier studies on these genotypes showed different levels of susceptibility to grapevine downy mildew (Plasmopara viticola). The aim of this work was to detect differences between the leaf morphology of these cultivars at the macro- and microscopic levels, and to characterize morphological traits which could be associated with susceptibility and resistance to downy mildew. An ampelographic description of each genotype was used to develop a scheme illustrating the characteristic leaf morphology. The density and morphology of the trichomes and the stomatal index was assessed by means of microscopical techniques. Distinct macro and microscope differences among the genotypes were seen. No clear relation between ampelographic characteristics and susceptibility to downy mildew was observed. The two cultivars that in earlier studies were found to be the least susceptible to downy mildew were the most similar in terms of their spongy mesophyll. Both showed very little or no wax on the abaxial surface of their leaves.

Modeling the ionizing spectra of H ii regions: individual stars versus stellar ensembles

Aims. We study how IMF sampling affects the ionizing flux and emission line spectra of low mass stellar clusters. Methods. We performed 2 x 10^6 Monte Carlo simulations of zero-age solar-metallicity stellar clusters covering the 20 - 10^6 Mo mass range. We study the distribution of cluster stellar masses, Mclus, ionizing fluxes, Q(H0), and effective temperatures, Tclus. We compute photoionization models that broadly describe the results of the simulations and compare them with photoionization grids. Results. Our main results are: (a) A large number of low mass clusters (80% for Mclus = 100 Mo) are unable to form an H ii region. (b) There are a few overluminous stellar clusters that form H ii regions. These overluminous clusters preserve statistically the mean value of obtained by synthesis models, but the mean value cannot be used as a description of particular clusters. (c) The ionizing continuum of clusters with Mclus < 10^4 Mo is more accurately described by an individual star with self-consistent effective temperature(T*) and Q(H0) than by the ensemble of stars (or a cluster Tclus) produced by synthesis models. (d)Photoionization grids of stellar clusters can not be used to derive the global properties of low mass clusters. Conclusions. Although variations in the upper mass limit, mup, of the IMF would reproduce the effects of IMF sampling, we find that an ad hoc law that relates mup to Mclus in the modelling of stellar clusters is useless, since: (a) it does not cover the whole range of possible cases, and (b) the modelling of stellar clusters with an IMF is motivated by the need to derive the global properties of the cluster: however, in clusters affected by sampling effects we have no access to global information of the cluster but only particular information about a few individual stars.Comment: A&A in pres

Broadband Faraday Isolator

Driving on an analogy with the technique of composite pulses in quantum physics, we propose a broadband Faraday rotator and thus a broadband optical isolator, which is composed of sequences of ordinary Faraday rotators and achromatic quarter-wave plates rotated at the predetermined angles.Comment: submitted to JOSA A, comments are welcom

Potential of MMP-9 based nanoparticles at optimizing the cow dry period: pulling apart the effects of MMP-9 and nanoparticles

The cow dry period is a non-milking interval where the mammary gland involutes and regenerates to guarantee an optimal milk production in the subsequent lactation. Important bottlenecks such as the high risk of intramammary infections complicate the process. Antibiotics have been routinely used as a preventive treatment but the concerns about potential antibiotic resistance open a new scenario in which alternative strategies have to be developed. Matrix metalloproteinase-9 (MMP-9) is an enzyme able to degrade the extracellular matrix, triggering the involution and immune function of cow mammary gland. We have studied the infusion into the mammary gland of MMP-9 inclusion bodies as protein-based nanoparticles, demonstrating that 1.2 mg of MMP-9 enhanced the involution and immune function of the cow mammary gland. However, the comparison of the efects triggered by the administration of an active and an inactive form of MMP-9 led to conclude that the response observed in the bovine mammary gland was mainly due to the protein format but not to the biological activity of the MMP-9 embedded in the inclusion body. This study provides relevant information on the future use of protein inclusion bodies in cow mammary gland and the role of MMP-9 at dry-of.info:eu-repo/semantics/publishedVersio