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Despite of a number of studies on the genetic nature of plant adaptation to drought stress there is still no conclusion on the core mechanism of defense. Extraction of knowledge gained from experiments on different plant species under different conditions and subsequent interpolation thus appears to be a challenge. Here we applied a sequence similarity-based approach to identify computationally the components of defense against water deprivation. The prediction in silico was based on the available scientific data. We identified a subset of defense gene candidates, of which 2 % were experimentally proven to be drought-responsive. The transcriptomic analysis of drought-stressed poplar roots generated data that confirm and/or complement previous reports on plant responses to drought. On the other hand, we observed suppression of genes involved in antioxidative defense that seems to contradict many foregoing observations. The results, advantages and possible drawbacks of our prediction approach are discussed in light of experimental data.

a b s t r a c t Long-term drought during one and two growing seasons, respectively strongly affected the timing and number of flushes of oak plants (Quercus robur L.), and negatively influenced subsequent growth. In con- trast, strong compensation growth was observed upon rewatering. The defence response of experimental plants was assessed by analyzing stress metabolites and transcriptome changes. Our data revealed that while during mild and/or short drought stress only readily metabolizable carbohydrates e.g. glucose, fructose, and galactose are accumulated, prolonged drought stress results in accumulation of more sta- ble and protective osmolytes such as quercitol and mannitol. At transcriptome level more than 3% of the expressed sequences tags (ESTs) represented on the microarray were differentially expressed reflecting the activation of defence responses in oak which appear to be stronger in the second year of persist- ing stress. The transcriptome changes are in good agreement with both the metabolic data as well as morphological observations. We conclude that mild long-term drought stress over two years triggers adaptation processes in oak plants that ensure survival, while irreversible damage is kept low facilitating full recovery upon rewatering. © 2011 Elsevier B.V. All rights reserved.

The origin of the putatively autotriploid plant with 2n=3X=24 chromosomes growing in Mediterranean and Near East countries is unclear. As saffron is male sterile and thus vegetatively propagated, it is assumed that there is just one saffron cultivar grown worldwide. Still there are differences in quality and phenotype reported, this being attributed to clonal differences. So far molecular analyses only concentrated on the identification of the putative ancestors of C. sativus L. using RAPD, AFLP, IRAP or ISSR markers, but no extensive study has been conducted to prove the genetic identity and the putative clonality of cultured saffron. In the limited phylogenetic studies conducted so far, C. sativus L. exhibited little to no genetic variation. In our study we concentrated on C. sativus L. exclusively, using maternally inherited choloropalst (cp) markers as well as microsatellite regions contained in expressed genes (EST-SSRs) to investigate genetic diversity. Out of the 6803 available saffron ESTs (D'Agostino et al., http://www.saffrongenes.org) 200 sequences proved to contain SSR regions. Out of these, for 38 sequences primers could be developed and tested on 29 different saffron accessions. In addition to the nuclear SSRs, 8 cp regions were investigated. Due to the fact that none of the regions revealed any genetic difference among the investigated probes, sequencing of 5 genes was conducted in order to identify single base pair mutations in the respective genomic areas.

Head 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.

A containment experiment was carried out in order to evaluate possible shifts in eubacterial and Pseudomonas rhizosphere community structures due to the release of genetically modified Basta-tolerant oilseed rape and the associated herbicide application. Treatments included cultivation of the transgenic plant as well as of the wild-type cultivar in combination with mechanical removal of weeds and the application of the herbicides Basta (active ingredient: glufosinate) and Butisan S (active ingredient: metazachlor). Rhizosphere soil was sampled from early and late flowering plants as well as from senescent plants. A culture-independent approach was chosen to characterize microbial communities based on denaturing gradient gel electrophoresis of 16S rRNA gene fragments amplified from rhizosphere DNA using eubacterial and Pseudomonas-specific PCR primers. Dominant pseudomonads in the rhizosphere were analyzed by sequence analysis. Whole community and Pseudomonas electrophoresis fingerprints revealed slightly altered microbial communities in the rhizosphere of transgenic plants; however, effects were minor as compared to the plant developmental stage-dependent shifts. Both herbicides caused transient changes in the eubacterial and Pseudomonas population structure, whereas differences due to the genetic modification were still detected at the senescent growth stage. The observed differences between transgenic and wild-type lines were most likely due to unintentionally modified plant characteristics such as altered root exudation.

Responses of plant tissue to environmental challenges can vary among different plant parts and among plants of different ages. Investment into defense has been proposed to be influenced by fitness value and/or allocation of available resources. Here we show at first time at transcriptome level that plant defense is non-linear. On very young, expanding, adult and old leaves of Populus nigra plants exposed to air perturbation, we studied the ontogenic trajectory of gene expression changes to such a low-dose factor similar to wind. Although plant responses to mechanical sensation (wind, touch) are described and summarized as thigmomorphogenesis, the knowledge on the molecular background of plant responses to wind is largely incomplete. Our data describe which genes are activated during a ubiquitous and continuous environmental factor such as wind, and based on existing knowledge complement the picture on ongoing processes.

Fusarium head blight (FHB, scab) is a fungal disease of wheat and other small cereals that is found in both temperate and semi-tropical regions. FHB causes severe yield and quality losses, but the most-serious concern is the possible mycotoxin contamination of cereal food and feed. Breeding for FHB resistance by conventional selection is feasible, but tedious and expensive. This study was conducted to identify and map DNA markers associated with FHB resistance genes in wheat. A population of 364 F(1)-derived doubled-haploid (DH) lines from the cross 'CM-82036' (resistant)/'Remus' (susceptible) was evaluated for Type II resistance (spread within the spike) during 2 years under field conditions. Marker analysis was performed on 239 randomly chosen DH lines. Different marker types were applied, with an emphasis on AFLP and SSR markers. Analysis of variance, as well as simple and composite interval mapping, were applied. Three genomic regions were found significantly associated with FHB resistance. The most-prominent effect was detected on the short arm of chromosome 3B, explaining up to 60% of the phenotypic variance for Type II FHB resistance. A further QTL was located on chromosome 5A and a third one on 1B. The QTL regions on 3B and 5A were tagged with flanking SSR markers, the 1B QTL was found associated with the high-molecular-weight glutenin locus. These results indicate that FHB resistance is under control of a few major QTLs operating together with unknown numbers of minor genes. Marker-assisted selection for these major QTLs involved in FHB resistance appears feasible and should accelerate the development of resistant and agronomically improved wheat cultivars.