Felix Briem

An invader supported by a parasite: Mistletoe berries as a host for food and reproduction of Spotted Wing Drosophila in early spring

The Spotted Wing Drosophila (SWD), Drosophila suzukii Matsumura, an invasive pest species in Europe and the Americas, is able to feed and reproduce on numerous fruit crops and a wide range of wild host plants. SWD is thought to overwinter outside of agricultural fields in forests and hedges. To identify overwintering sites and early spring oviposition hosts, traps were installed in forests. In spring 2015, traps in the canopy of pine trees parasitized by mistletoe, Viscum album subsp. laxum, captured significantly more SWD than traps in pine trees without mistletoe. We found SWD females with ripe eggs coinciding with ripening and ripe mistletoe berries. We investigated whether mistletoe may serve as a host for SWD. Under laboratory conditions, SWD developed from egg to adult in mistletoe berries. More adults emerged from wounded berries. Females were observed to feed on berries and survived up to eight days without other food. A few adults emerged from wild mistletoe berries. To understand the attraction of SWD to parasitized trees, we analyzed the volatile organic compounds (VOCs) collected from the headspace of mistletoe berries by GC–MS and identified the main components. Thirty-two VOCs were found. Wounded and unwounded berries differed significantly in the quantity of 11 VOCs emitted. The odor spectrum showed many similarities to other typical berry odors. The combination of field surveys and laboratory assays identified a new reproduction host for SWD in spring. This host plant may help SWD to withstand the bottleneck period for survival in winter and spring.

Response of Drosophila suzukii (Diptera: Drosophilidae) to extreme heat and dryness

Drosophila suzukii Matsumura (Diptera) is a polyphagous herbivore native to East Asia that develops in cultivated and wild fruits. In 2011, it appeared in Germany. In 2012, economic damage was recorded and, in 2014, the harvest of stone and soft fruits was lost in some regions. By contrast, during 2015, populations remained lower. Record temperatures and dryness might have impeded population growth during that year. To test this hypothesis, flies were exposed to a 4‐day simulation. We evaluated the effect of fluctuating temperature and humidity on mortality and reproduction of D. suzukii from three age classes (average age: class 1: 3 days; class 2: 11 days; class 3: 20 days). Maximum temperatures were 27, 33 and 39 °C. Relative humidity oscillated between 18% and 85%. Fly mortality through heat stress ranged from 50% to 80%. Higher rates died of oldest flies and females. Offspring per female did not differ between heat stressed and control groups. Flies of both sexes were not sterilized through heat and dryness. Prior acclimation reduced any negative effects. We concluded that heat waves and extreme dryness during 2015 were one cause of the low population densities of D. suzukii observed under field conditions.

Molekulare Nahrungsanalyse bei der invasiven Kirschessigfliege,Drosophila suzukii

Recent studies on endophytic Kosakonia radicincitans DSM 16656T demonstrated a wide plant growth-promoting activity. The application of this Gram-negative bacterium as a biofertilizer is limited due to the lack of adequate formulation that protects the cells during drying and storage and supports plant colonization. Here we set out to elucidate the compatible solutes accumulation influence of K. radicincitans triggered by osmotic stress on its capacity as an endophyte in radish plants. We found that physiological modifications by osmotic stress treatments and accumulation of compatible solutes during cultivation, improve the capability of K. radicincitans formulated in dry beads to colonize and to promote radish growth. Thus, pre-conditioning of cells with NaCl 4% and by adding compatible solutes such as hydroxyectoine during cultivation induced a positive effect on relative gene expression response, enhancing significantly the ability to colonize plant tissue up to 10 fold. Additionally, when this osmolyte was added, either dry matter of tuber or leaves increased by 3 % and 13.59 %, respectively in comparison to beads without the bacterium. These first results indicate that a systematic approach to cultivation and formulation may increase the endophytic capacity of this bacterium.

DrosoMon: Ein Web-basiertes Monitoring-, Analyse- undVisualisierungswerkzeug zum Auftreten und der Ausbreitung derKirschessigfliege

Recent studies on endophytic Kosakonia radicincitans DSM 16656T demonstrated a wide plant growth-promoting activity. The application of this Gram-negative bacterium as a biofertilizer is limited due to the lack of adequate formulation that protects the cells during drying and storage and supports plant colonization. Here we set out to elucidate the compatible solutes accumulation influence of K. radicincitans triggered by osmotic stress on its capacity as an endophyte in radish plants. We found that physiological modifications by osmotic stress treatments and accumulation of compatible solutes during cultivation, improve the capability of K. radicincitans formulated in dry beads to colonize and to promote radish growth. Thus, pre-conditioning of cells with NaCl 4% and by adding compatible solutes such as hydroxyectoine during cultivation induced a positive effect on relative gene expression response, enhancing significantly the ability to colonize plant tissue up to 10 fold. Additionally, when this osmolyte was added, either dry matter of tuber or leaves increased by 3 % and 13.59 %, respectively in comparison to beads without the bacterium. These first results indicate that a systematic approach to cultivation and formulation may increase the endophytic capacity of this bacterium.

Explorative Data Analysis of Drosophila suzukii Trap Catches from a Seven-Year Monitoring Program in Southwest Germany

Over the last decade, Drosophila suzukii Matsumura, an invasive pest of soft-skinned fruits, gradually established itself in Europe, often resulting in significant economic losses. In 2011, when D. suzukii was first described for Germany, the Julius Kühn Institut (JKI) started a monitoring program in southwest Germany to study the occurrence and activity of the fly. Capture data from late 2011–early 2018 from 100 traps were analyzed for the effect of weather and immediate habitat on trap captures at different times of the year. We identified five phases in the annual population development cycle of D. suzukii. We found that the mild winter of 2013/2014 helped the thorough establishment of D. suzukii in Germany. Habitat types in the immediate vicinity of the trap and local weather conditions had a strong influence on trap captures. Forest borders and hedges were found to provide adequate overwintering shelter for the flies. Trap captures in forests and hedges were generally higher than those of vineyards and orchards, even during the fruiting seasons. Summer capture rates were correlated with the number of heat days and precipitation. We also discuss briefly the limitations of using trap captures as representative of fly density in the field.

Variety-depending susceptibility of cherries to Drosophila suzukii according to fruit firmness and other ripening parameters

Ryegrass (Lolium spec.) is the most important cool-season forage crop in temperate regions. Though, the seed production is considerably affected by several fungal and bacterial obligate biotrophic pathogens. The overall purpose of this study is directed to developing ryegrass cultivars with multiple pathogen resistance and agronomic adaption to Germany’s agricultural conditions. This aim shall be achieved by combining genes for resistances to stem rust, crown rust and bacterial wilt. The pyramidisation shall be accomplished by the use of specific molecular markers which will be derived by bulked segregant analysis combined with next generation sequencing based massive analysis of cDNA ends (MACE) transcriptome profiling. RNA was isolated from bulks of infected and noninfected leaf segments from susceptible and resistant genotypes of various fullsibling mapping populations (n ≥ 200) and their respective parental lines for every investigated pathogen. After MACE was performed, bioinformatic analysis detects SNPs and transcripts that were exclusively expressed in the resistant bulk. Thus, 30 molecular markers were genetically mapped to a 50.8 cM spanning region surrounding the stem rust resistance locus LpPg1. The development of this high efficient molecular selection tool marks MACE as a fast and reliable method that detects polymorphisms for genetic mapping of candidate genes and obtains to be the method of choice for investigating the molecular and genetic base of resistances to stem rust, crown rust and bacterial wilt.The current production systems in arable farming have reached their limits. Sizes of machinery are continuously increasing. Compaction and limits on the road are the consequences. Productionrelated restrictions like nitrogen pressure and development of resistances against plant protection products are further problems. Last but not least, the sociopolitical acceptance of crop production is questioned in public opinion. Due to these circumstances the question arises if the system of crop farming which has been adapted to the machinery available on the market is the right strategy for the future. Why not going the other way round and decide what a plant production system has to look like to be at an optimum and then decide what kind of machinery is needed to cultivate? Following this idea the plants must be in the focus.