Génétique des populations et lutte contre le phylloxéra

Dans le passé, le phylloxéra était le ravageur le plus important de nos vignobles. Cependant, le greffage de variétés européennes sur des porte-greffes américains tolérants au puceron a permis d’enrayer ses dégâts à la fin du XIXe siècle. Malgré ce succès, le phylloxéra est encore présent dans toutes les régions de Suisse et provoque ponctuellement la formation massive de galles foliaires, en particulier sur les cépages interspécifiques. Nous donnons ici un aperçu de la structure génétique des populations locales de phylloxéra et présentons les résultats de deux essais de lutte

Populationsgenetik und Bekämpfung der Reblaus

Die Reblaus war gegen Ende des 19. Jahrhunderts wohl der gefährlichste Rebschädling. Durch Pfropfung anfälliger europäischer Sorten auf reblaustolerante amerikanische Unterlagen konnte die Gefahr gebannt werden. Aber auch heute noch kommt die Reblaus fast überall in der Schweiz vor und bildet auf interspezifischen Rebsorten oft massiv Blattgallen. Der Beitrag gibt Einblick in die genetische Struktur dieser Reblauspopulationen und in die Ergebnisse von zwei Wirkungsversuchen

A tripartite aseptic culture system for grape (Vitis spp), phylloxera (Daktulosphaera vitifoliae) and mites (Tarsanemus sp.)

Research Not

Aseptic dual culture of grape (Vitis spp.) and grape phylloxera (Daktulosphaira vitifoliae FITCH)

An aseptic dual culture of grape phylloxera (Daktulosphaira vitifoliae FITCH) and grape vine (Vitis spp.) was developed. This method permits continuous observation of phylloxera feeding and the whole plant response on a dynamic basis. The plant/parasite interaction of three testplants (V. vinifera L., var. Riesling, SO 4 (V. berlandieri PLANCH. X V. riparia L.) and V. riparia, var. Gloire de Montpellier) are demonstrated by observing post-infectious reactions of the host- and population dynamics of the parasite. Different stages of phylloxera could be observed including nymphs, winged phylloxera (alatae) and sexual male phylloxera. Several potential applications for this aseptic dual culture are demonstrated

A double-sigmoid model for grapevine bunch compactness development

Aim Bunch compactness is the result of a complex dynamic process in which many bunch, berry and rachis features interact during the whole grapevine reproductive cycle. The aim of this work is to identify the different developmental stages involved in bunch compactness determination during the second growing season, from full-flowering to harvest time. Methods and Results In this work, bunch features from ten wine grapevine cultivars with diverse bunch compactness (including very loose and very compact bunches) have been periodically described. Experimental data allowed us to quantify changes in bunch compactness from berry set until harvest time in an objective manner. Our results indicate that bunch compactness development follows a double-sigmoid model, characterized by two consecutive cycles, each one with a growing stage followed by a latent one. Differences in the slope factor of the growing stages and in the duration of each developmental phase can explain part of the bunch compactness variation observed in our set of cultivars. Conclusions Two consecutive sigmoid cycles with four different stages can be observed in the determination of grapevine bunch compactness. Bunch architecture before véraison plays an important role in the final compactness of the bunch at harvest time. Significance and impact of the study The double-sigmoid model for bunch compactness development, and the four different stages identified will aid in future analyses aimed to unravel the underlying mechanisms affecting this complex trait

Karyotype studies on grape phylloxera (Daktulosphaira vitifoliae FITCH)

A cytogenetic technique was developed to produce suitable chromosome spreads for phylloxera karyotype analysis. The karyotype for pathogenetic phylloxera was 2 n = 10. Karyotypes from haploid sex cells were found to vary between n = 5 and n = 6, the latter possibly indicating an aneuploidic aberration. Tetra- and polyploid cells were detected in somatic trophocytes. Preparation of phylloxera sex and somatic cells for chromosomal analysis reported here enables the study of genetic variation on a chromosomal scale

The role of the secondary phloem during the development of the grapevine Berry Shrivel ripening disorder

Berry Shrivel (BS) is a post-veraison physiological ripening disorder of grapevine berries. Its symptoms encompass low pH, reduced content of sugars and anthocyanins, and loss of turgor leading to berries shriveling. Evidence for the primary causes of BS is still speculative and anatomical studies are scarce. So far, anatomical studies have determined necrotic cells, degraded primary phloem cells and hardening of secondary phloem cells in the rachis of BS affected grapes. The picture is far from being complete. Herein we report in-depth analyses of the ultrastructure, anatomy and spatial elementary analysis of rachis and pedicel tissues of BS symptomatic grape clusters with different symptom severity. We hypothesize that structural changes in the vascular system of BS affected grape clusters could alter transport functions of the phloem tissue and contribute to the appearance of BS symptoms. By applying different microscopic techniques (LM, SEM, TEM and EDS) we found a number of anatomical differences in both, rachis and pedicels, between H and BS symptomatic grapes, which include: (i) extended areas of collapsed cells and cell wall thickenings in the secondary phloem in BS samples; (ii) reduced number of cell layers in the cambium in BS samples; (iii) higher rate of callose deposition on sieve plates that are additionally covered with a carbohydrate-like material in BS samples; and (iv) reduced (up to 60%) estimated sieve tube conductivity in BS samples.The project was supported by the bilateral exchange and cooperation program between Austria and Poland (WTZ) project no. PL 08/2015 (9196) and by the Austrian Science Fund (FWF) project no. P 28966-B29