M. Griesser

Variation for resistance to head blight caused by Fusarium graminearum in wild emmer (Triticum dicoccoides) originating from Israel

AbstractHead blight of wheat (FHB, scab) caused by Fusarium spp. has been associated with yield and quality losses in many wheat-growing regions. In tetraploid wheat sources of resistance are scarce. In the search for novel sources of resistance, 151 Triticum dicoccoides genotypes, originating from 16 habitats in Israel and one habitat in Turkey together with several control genotypes, were evaluated for reaction to fungal spread (Type II resistance) in replicated greenhouse experiments. Significant genetic diversity was found among the tested genotypes, the broad sense heritability for Type II FHB resistance was 0.71. Most of the tetraploid accessions were highly susceptible, only a few showed moderate resistance. Among the eight T. dicoccoides lines with the lowest relative infection rates, five originated from the Mt. Gerizim population, and three from the Mt. Hermon population. None of the T. dicoccoides lines reached the level of resistance present in the common wheat cultivar Sumai3.

Severe drought stress is affecting selected primary metabolites, polyphenols, and volatile metabolites in grapevine leaves (Vitis vinifera cv. Pinot noir)

Extreme weather conditions with prolonged dry periods and high temperatures as well as heavy rain events can severely influence grapevine physiology and grape quality. The present study evaluates the effects of severe drought stress on selected primary metabolites, polyphenols and volatile metabolites in grapevine leaves. Among the 11 primary metabolites, 13 polyphenols and 95 volatiles which were analyzed, a significant discrimination between control and stressed plants of 7 primary metabolites, 11 polyphenols and 46 volatile metabolites was observed. As single parameters are usually not specific enough for the discrimination of control and stressed plants, an unsupervised (PCA) and a supervised (PLS-DA) multivariate approach were applied to combine results from different metabolic groups. In a first step a selection of five metabolites, namely citric acid, glyceric acid, ribose, phenylacetaldehyde and 2-methylbutanal were used to establish a calibration model using PLS regression to predict the leaf water potential. The model was strong enough to assign a high number of plants correctly with a correlation of 0.83. The PLS-DA provides an interesting approach to combine data sets and to provide tools for the specific evaluation of physiological plant stresses.

Phylloxera (Daktulosphaira vitifoliae Fitch) alters the carbohydrate metabolism in root galls to allowing the compatible interaction with grapevine (Vitis ssp.) roots

Highlights • Sucrose is transported symplastically towards developing and growing nodosities.• Starch is accumulated and metabolized during nodosities growth and development.• Nodosity formation has systemic effects on non-infected root tips of phylloxerated plants.• Gall formation reprograms processes of the secondary metabolism as demonstrated transciptionally.

Expression of putative expansin genes in phylloxera (Daktulosphaira vitifoliae Fitch) induced root galls of Vitis spp.

Grape phylloxera (Daktulosphaira vitifoliae Fitch) is a serious global pest in viticulture. The insects are sedentary feeders and require a gall to feed and reproduce. The insects induce their feeding site within the meristematic zone of the root tip, where they stay attached, feeding both intra- and intercellularly, and causing damage by reducing plant vigour. Several changes in cell structure and composition, including increased cell division and tissue swelling close to the feeding site, cause an organoid gall called a nodosity to develop. Because alpha expansin genes are involved in cell enlargement and cell wall loosening in many plant tissues it may be anticipated that they are also involved in nodosity formation. To identify expansin genes in Vitis vinifera cv. Pinot noir, we mined for orthologues genes in a comparative analysis. Eleven putative expansin genes were identified and shown to be present in the rootstock Teleki 5C (V. berlandieri Planch. x V. riparia Michx.) using specific PCR followed by DNA sequencing. Expression analysis of young and mature nodosities and uninfested root tips were conducted via quantitative real time PCR (qRT-PCR). Up-regulation was measured for three putative expansin genes (VvEXPA15, -A17 and partly -A20) or down-regulation for three other putative genes (VvEXPA7, -A12, -A20) in nodosities. The present study clearly shows the involvement of putative expansin genes in the phylloxera–root interaction.

Expansins are among plant cell wall modifying agents specifically expressed during development of nematode-induced syncytia

Cyst nematodes are economically important pests. As obligatory biotrophic endoparasites they invade host roots and induce formation of syncytia, structures that serve them as the only source of nutrients. During syncytium development, extensive cell wall modifications take place. Cell wall dissolution occurs during cell wall opening formation, cell walls expand during hypertrophy of syncytial elements and local cell wall synthesis leads to the thickening of syncytial cell wall and the formation of cell wall ingrowths. Numerous studies revealed that nematodes change expression of plant genes encoding cell wall modifying proteins including expansins. Expansins poses unique abilities to induce cell wall extension in acidic pH. Recently, we demonstrated that two α-expansin genes LeEXPA4 and LeEXPA5 are up-regulated in tomato roots infected with potato cyst nematode (Globodera rostochiensis). In this addendum, we present the most recent results concerning involvement of plant cell wall modifying genes in syncytium development and discuss possible practical applications of this knowledge for developing plants with resistance against nematodes. Addendum to: Fudali S, Janakowski S, Sobczak M, Griesser M, Golinowski W, Grundler FMW. Two tomato α-expansins show distinct spatial and temporal expression patterns during development of nematode induced syncytia. Physiologia Plantarum 2008; 132:370-83.

No evidence of superclones in leaf-feeding forms of austrian grape phylloxera (Daktulosphaira vitifoliae)

The genetic structure of ten grape phylloxera populations, sampled in summer of 2006 and 2007 from four distinct viticultural areas in Austria, Daktulosphaira vitifoliae (Fitch) (Homoptera: Phylloxeridae) was analyzed using six SSR markers (Dvit1-Dvit6). Leaf-feeding populations were chosen from similar ecological habitats, where susceptible rootstock hosts have overtaken scions in abandoned vineyards and produce grape phylloxera populations. To study population structures and test for dominating genotypes, population genetic measures were performed. The genetic diversity detected within the entire set of 315 genotypes was high, with 223 distinct multilocus genotypes (MLGs). Excess of heterozygotes and significant deviations from Hardy-Weinberg equilibrium in some populations indicated that the major reproduction mode in these populations is asexual but, sexual reproduction also confirmed by the sign. Psex values. The genetic diversity within populations was higher than between populations, although only three overlapping genotypes could be found. MLGs were rare, indicating that no candidate for superclones were detected in the leaf-feeding populations studied.

Quantification of tomato expansins in nematode feeding sites of cyst and root-knot nematodes

Sedentary endoparasitic nematodes induce specific feeding structures in roots of their host plants. The cyst nematode Globodera rostochiensis induces syncytia that are formed by local cell wall degradation, subsequent fusion of the protoplasts and hypertrophy. Root-knot nematodes such as Meloid-ogyne incognita induce galls containing giant cells which differentiate by rapid expansion and nuclear divisions in absence of cytokinesis. Specific cell wall modifications such as expansion, bending and thickening are prominent in both systems. Therefore we investigated gene expression patterns and localization of expansins in a comparative analysis. Expansins are cell wall loosening proteins involved in growth and cell wall disassembly. The expression of expansins in syncytia of G. rostochiensis in tomato and in syncytia and galls induced in Arabidopsis thaliana has already been described. We provide additional information on the expression of 10 tomato expansin isoforms, namely LeEXPA1, -2, -3, -4, -5, -8, -9, -10, -11 and -A18 in 5- and 10-day-old galls of M. incognita with sqRt-Pcr. Further, we determined the quantitative expression of seven differentially regulated tomato expansins in syn-cytia and galls at different developmental stages. We observed a very high induction of LeEXPA2, -5 and -11 with maxima in 10-day-old syncytia and 5-day-old galls. Other members of the gene family were slightly induced in syncytia, whereas in galls only LeEXPA2, -5 and -11 were found to be upregulated. Previous results on the expression of LeEXPA5 in galls are confirmed and detail new information on expansin expression in nematode feeding site is provided. LeEXPA4 and LeEXPA5 have been localized in syncytia recently and we could confirm these results with in situ Rt-Pcr. LeEXPA1, -2, -9, -11 and -18 were also detected in 5- and 10-day-old syncytia and neighboring cells. Especially the expression pattern of LeEXPA2 and LeEXPA5 is of interest, because of their low expression in uninfected roots but their high induction in nematode feeding sites. Our results confirm that expansins are differentially regulated during formation of both syncytia and galls and indicate that these genes are involved in cell wall modifying processes during plant nematode interactions.ZusammenfassungSedentäre Nematoden induzieren spezifische Nährzellen in den Wurzeln ihrer Wirtspflanzen. Der Zystennematode Globodera rostochiensis bildet Syncytien, die durch lokalen Zellwandabbau und anschließende Fusion und Hypertrophie der Protoplasten entstehen. Wurzelgallennematoden wie z.B. Meloidogyne incognita verursachen die Bildung von Gallen, die so genannte Riesenzellen enthalten, die durch eine rasch fortschreitende Expansion und eine unvollständige Zellteilung ohne Zytokinese entstehen. In beiden Systemen treten deutliche Zellwandveränderungen wie Expansion, Verdickungen und Verkrümmungen auf. Daher wurden Expressionsmuster und die Lokalisation von Expansinen in einer vergleichenden Analyse untersucht. Expansine sind Zellwand modifizierende Proteine, die generell in Wachstumsprozessen von Pflanzenzellen involviert sind. Die Expression von Expansinen in Syncytien in Tomaten und Syncytien und Wurzel-gallen in Arabidopsis thaliana wurde bereits nachgewiesen. Hier werden detaillierte Informationen zur Expression von 10 Tomaten-Expansin Isoformen, den Genen LeEXPA1, -2, -3, -4, -5, -8, -9, -10, -11 und -A18 in 5 und 10 Tage alten Wurzelgal-len anhand von sqRt-Pcr Analysen gegeben. Darüber hinaus erfolgte eine quantitative Analyse der Expression von sieben differentiell regulierten Expansinen in Syncytien und Gallen zu verschiedenen Entwicklungszeitpunkten. Dabei konnten eine starke Induktion von LeEXPA2, -5 and -11 mit Maximal-werten in 10 Tage alten Syncytien und 5 Tage alten Gallen beobachtet werden. Mehrere weitere Expansine waren in Syncytien noch induziert, während in Gallen nur LeEXPA2, -5 and -11 aufreguliert waren. Damit könnten frühere Resultate zur Expression von LeEXPA5 in Gallen bestätigt werden. Auch die Lokalisation von LeEXPA4 and LeEXPA5 in Syncytia konnte mit Hilfe der in situ Rt-Pcr bestätigt werden. Daneben wur-den aber auch LeEXPA1, -2, -9, -11 and -18 5 und 10 Tage alten Syncytien und benachbarten Zellen detektiert. Als besonders interessant erwies sich das Expressionsmuster von LeEXPA2 und LeEXPA5, da diese Gene in der nicht infizierten Wurzel praktisch nicht induziert werden, in den Nährzellen jedoch sehr stark. Gesamt betrachtet bestätigen die Resultate frühere Untersuchungen zur Expansinsexpression in nematodenindu-zierten Nährzellen und weisen darauf hin, dass Mitglieder dieser Genfamilie für die Nährzellenbildung von ausschlag-gebender Bedeutung sind.

The ripening disorder berry shrivel affects anthocyanin biosynthesis and sugar metabolism in Zweigelt grape berries

AbstractMain conclusionTimescale analyses suggest the berry shrivel (BS) disorder is induced before veraison with strong effects on anthocyanin biosynthesis, and minor effects on sugar transport and metabolism. Berry shrivel (BS)-affected grapes have low sugar contents, high acidity, less anthocyanins and flaccid berries. To date no pathogenic causes are known, and studies to elucidate the molecular basis leading to symptom induction and development are limited. Here we present a study on pre-symptomatic as well as symptomatic BS berries to characterize early metabolic changes, with focus on anthocyanin biosynthesis and sugars metabolism. Healthy and BS berries from six sampling time points were used (BBCH79–BBCH89). Our objectives are (1) to search for the beginning of BS-related physiological processes; (2) to search for key enzymes and sugar transporters involved in BS induction and development and (3) to understand the consequences on polyphenol biosynthesis. We employed high performance anion exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD) and liquid chromatography–tandem mass spectrometry (LC–MS/MS) technology for sugar and polyphenol analyses, respectively. Additionally we conducted expression analyses (qPCR) of key genes and enzymatic activity assays. Our results show that BS-related processes start before veraison, as determined by slightly reduced hexose contents and reduced expression levels of a vacuolar invertase (VviGIN1), two monosaccharide transporters (VviTMT2, VviTMT3) and the anthocyanin biosynthesis (VviUFGT, VviMYBA1/2) genes. Lower amounts of delphinidin and cyanidin glycosidic forms were determined, while caftaric acid, quercetin-3-O-glucuronide and (+)-catechin were increased in BS berries. Although not all results were conclusive, especially for the sugar metabolism, our data provide important knowledge to improve the understanding of the highly complex berry shrivel ripening disorder.

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.