Variability of aliphatic glucosinolates in Arabidopsis thaliana (L.) – Impact on glucosinolate profile and insect resistance

The glucosinolate(GS)-myrosinase system of Brassicaceae, including the model plant Arabidopsis thaliana (L.), comprises a defence which is effective especially against generalist herbivores. Based on their side chain structure GS are grouped into aliphatic, aromatic, and indolyl GS. Indolyl GS are widely distributed among A. thaliana ecotypes and the Brassicaceae family, but the presence of aliphatic GS is variable and under strong genetic control. We investigated the effect of AOP gene expression on the side chain modifications of GS and the impact on insect resistance. AOP2 and AOP3 genes from Mr-0 and Sap-0 ecotypes, respectively, were crossbred into the methylsulfinyl GS producing Gie-0. Successful crosses were heterozygote plants which produced allyl (AOP2) or 3-hydroxypropyl GS (AOP3). After self-pollination, the chemical profile of the F3 generation of plants was screened to identify homozygote lines. Homozygote lines producing 3-hydroxypropyl GS were compared to methylsulfinyl GS, which were used to study the impact of GS structure on insect performance in first experiments. Our experiments revealed that methylsulfinyl GS containing ecotype lines were more resistant to the generalist caterpillar Spodoptera exigua (Hübner) and to the specialist caterpillar Pieris brassicae (L.) than the lines containing hydroxypropyl GS as main compounds

The cosmic ray spectrum above 10(17) eV

The final analysis of the data obtained by the Sydney University Giant Airshower Recorder (SUGAR) is presented. The data has been reanalysed to take into account the effects of afterpulsing in the photomultiplier tubes. Event data was used to produce a spectrum of equivalent vertical muon number and from this a model dependent primary energy spectrum was obtained. These spectra show good evidence for the Ankle: a flattening at 10(19) eV. There is no sign of the cut-off which would be expected from the effects of the universal black body radiation

Neural changes when actions change: Adaptation of strong and weak expectations

Repeated experiences with an event create the expectation that subsequent events will expose an analog structure. These spontaneous expectations rely on an internal model of the event that results from learning. But what happens when events change? Do experience-based internal models get adapted instantaneously, or is model adaptation a function of the solidity of, i.e., familiarity with, the corresponding internal model? The present fMRI study investigated the effects of model solidity on model adaptation in an action observation paradigm. Subjects were made acquainted with a set of action movies that displayed an altered script when encountered again in the scanning session. We found model adaptation to result in an attenuation of the premotor-parietal network for action observation. Model solidity was found to modulate activation in the parahippocampal gyrus and the anterior cerebellar lobules, where increased solidity correlated with activity increase. Finally, the comparison between early and late stages of learning indicated an effect of model solidity on adaptation rate. This contrast revealed the involvement of a fronto-mesial network of Brodmann area 10 and the ACC in those states of learning that were signified by high model solidity, no matter if the memorized original or the altered action model was the more solid component. Findings suggest that the revision of an internal model is dependent on its familiarity. Unwarranted adaptations, but also perseverations may thus be prevented

Influence of the season on the salicylate and phenolic glycoside contents in the bark of Salix daphnoides, Salix pentandra, and Salix purpurea

Due to the benefits of herbal medicine and their wide range of application for human health, the usage of natural drug products, such as willow bark extract, has increased in the last few years. The principle active compounds of the drugs comprised primarily of willow bark are phenolic glycosides like salicylates. Phenolic glycoside profiles of bark vary among species and between the seasons. To identify and preserve willow clones with high salicylate content for possible commercial usage at a later stage, we have screened three Salix sp. in respect to their chemical profiles. The willow species analysed were: Salix daphnoides, Salix pentandra, and Salix purpurea. These species had distinct phenolic glycoside profiles. The major salicylate of S. daphnoides and S. purpurea clones was salicortin, whereas the main compound of S. pentandra was 2’- O-acetylsalicortin. According to the chemical profiles of 140 clones, seven independent clones of S. daphnoides and S. purpurea as well as four clones of S. pentandra with high phenolic glycoside contents were picked to study seasonal changes in bark chemistry. Overall, the clones of S. daphnoides showed the highest mean salicylate and phenolic glycoside contents, followed by S. pupurea and S. pentandra. The secondary metabolite content of willow bark clones decreased during the vegetative season from March to June 2007 and further from June to July 2007. Our study revealed that for optimum yield of phenolic glycosides the species, the clone, and the time of harvest during the season have to be taken in consideration

Impact of glucosinolate structure on the performance of the crucifer pest Phaedon cochleariae (F.)

Glucosinolates (GS) are sulfur-rich secondary metabolites found in the Brassicaceae and other related families of the order Brassicales. GS consist of structurally-related compounds with different side chains. To explore the possibility that various side chain confer divergent biological activities to individual GS, we have investigated the performance of the specialist pest beetle, Phaedon cochleariae (F.) on Arabidopsis thaliana L. mutants and Columbia wild-type (WT) which differ in the main group of GS. Plant lines of A. thaliana altered for the expression of MAM3, because of the introduction of an overexpression construct of MAM3 (mam3+) or containing double knockouts of CYP79B2 and CYP79B3 (cyp79B2-/cyp79B3-) were used for the study in comparison to the WT.A. thaliana genotypes differed in their GS profiles. The highest GS content was present in the WT followed by mam3+ and cyp79B2-/ cyp79B3-. A modified aliphatic GS content was detected for the mam3+ as compared to the WT lines. Furthermore, indolyl GS were completely absent in cyp79B2-/cyp79B3-. The percentage weight increase of larvae raised on each of the three plant genotypes was significant different. Larval performance was poorest on plants of cyp79B2-/cyp79B3- and best on WT, but there was no significant difference found in percentage weight increase on mam3+ and WT. There was no correlation between the weight increase of the larvae on genotypes and induced levels of aliphatic, indolyl, and total GS. However, the poor performance of beetle larvae on cyp79B2-/ cyp79B3-compared to WT and mam3+ might be explained by comparable high aliphatic GS levels of this mutant, a different induction of secondary metabolites, and the absence of indolyl GS. Basic knowledge about the relationship of GS structures and their insect pests may help in further resistance breeding of crucifer crops

Parthenium Weed (Parthenium hysterophorus L.) Research in Ethiopia: Impacts on Food Production, Plant Biodiversity and Human Health

The highly competitive, adaptable and allergenic weed Parthenium hysterophorus (Compositae) is an invasive annual weed believed to be introduced to Ethiopia in 1970s. Field surveys, plant biodiversity impacts, and analysis of secondary plant compounds in P. hysterophorus and its possible impact on human health have been studied in Ethiopia since 1998. The weed has invaded a variety of habitats ranging from roadsides to grasslands and crop fields. Infestations were found to be greater than 20 plants per m2 and yield losses in sorghum reached 46-97% depending on the location and year. In grasslands dominated by parthenium, native plant species composition and abundance was found to be low. Manual control of parthenium by farmers resulted in the development of skin allergies, itching, fever, and asthma. These reactions could be attributed to the presence of secondary plant compounds (parthenin, chlorogenic acid, isocholorogenic acid, vanilic acid and caffeic acid) which were found in parthenium with significant variation in their concentrations among the different plant parts, dependent on plant locality, moisture content and plant size. The social cost of parthenium in Ethiopia was measured by Disability Adjusted Life Years and its equivalence in terms of monetary value was estimated at US$ 2,535,887 - 4,365,057. More resources have to be invested to tackle the parthenium problem as the estimated loss is disproportionate to the cost of investment in parthenium research and development activities

Exceeding the threshold value for Trioza apicalis Förster 1848 in carrot fields did not cause damage as revealed during monitoring in Germany from 2017–2020

The carrot psyllid Trioza apicalis Förster 1848 is a carrot pest in Europe that can cause serious damages in case of massive occurrence. Damages up to a total loss of yield have been reported from Scandinavian countries but also from Switzerland. The action threshold to control the pest with chemical pesticides is 0.2 T. apicalis per day and trap caught by sticky traps. We investigated the number of T. apicalis with sticky traps on carrot fields of the study regions Lüneburg/Uelzen and Hameln/Bad Pyrmont in Germany, during the period 2017–2020. The number of T. apicalis caught was generally very low in both study regions. On several fields in successive weeks almost no individuals were found in the study region Hameln/Bad Pyrmont. In Lüneburg/Uelzen was at least one field each year where the number of carrot psyllid was clearly higher than in all other fields and exceeded the threshold level. Surprisingly on carrot fields in close proximity to carrot fields from the previous year, the T. apicalis numbers were only slightly increased. Nonetheless, no loss of yield was reported for any of the fields in the four years of the study, although the generally defined threshold has been exceeded on many of the investigated carrot fields

Parthenium weed (Parthenium hysterophorus L.) research in Ethiopia: Investigation of pathogens as biocontrol agents

Parthenium is an exotic invasive weed that now occurs widely in Ethiopia. Surveys to determine the presence and distribution of pathogens associated with parthenium and further evaluation of the pathogens found as potential biocontrol agents were carried out in Ethiopia since 1998. Several fungal isolates of the genus Helminthosporium, Phoma, Curvularia, Chaetomium, Alternaria, and Eurotium were obtained from the seeds and other plant parts. However, all of the isolates tested were non-pathogenic except Helminthosporium isolates. The two most important diseases were the rust, Puccinia abrupta var. partheniicola and the phyllody, caused by a phytoplasma belonging to the species “Candidatus Phytoplasma aurantifolia”. Host specificity tests revealed that the rust, P. abrupta, only sporulates on parthenium while the phyllody infected parthenium, groundnut, sesame, grass pea, lentil, and chickpea. Suspected insect vectors were examined for phytoplasma infection by means of Polymerase Chain Reaction (PCR). The successful acquisition of phytoplasma’s by the leafhopper, Orosius cellulosus Lindberg (Cicadellidae), was determined by molecular detection of phytoplasma. Phytoplasma was also detected from a single bait plant after feeding by the leafhopper. Sequencing data from phytoplasma obtained from parthenium and the above mentioned crops was identical with sequence identities > 98%. The rust was commonly found at 1400 – 2500 m.a.s.l. with disease incidence up to 100% in some locations while phyllody was observed at 900 – 2300 m.a.s.l. with incidence up to 75%. Individual effects of the rust and phyllody diseases on Parthenium in different locations under field condition showed significant reduction on seed and morphological parameters. Seed production was reduced by 42 and 85% due to rust and phyllody, respectively