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First Report of Pseudomonas syringae pv. aptata Causing Bacterial Leaf Spot on Sugar Beet in Serbia
No full textWheat seedlings growth response to water deficiency and how it correlates with adult plant tolerance to drought
No full textImproving resistance to water and osmotic stresses at the seedling stage is becoming a much more important target for wheat breeders due to an increase in the frequency and severity of drought occurrences at the crop establishment and tillering phases in many wheat growing areas of the world. Ninety-six diverse wheat genotypes were laboratory tested for germination and growth response under osmotic stress induced by polyethylene glycol (PEG). Germination percentage, mean germination time, coleoptile length, shoot length and shoot growth rate were compared under stress (-0.4 MPa) and control (0.0 MPa) conditions. The same genotypes were previously grown in field trials exposed to drought stress during the anthesis and/or grain filling growth stage along with control (optimum) conditions. Grain yield (GY) and 19 other traits of agronomic importance (earliness, stem-related traits, number of kernels, mass of 1000 grains, etc.) were recorded. All seedling traits under PEG-induced water stress showed the highest relationship with the stem and stem-related traits of adult plants. To study the correlation between stress tolerance in the seedling and reproductive stages, three stress indices (tolerance index (TOL), stress susceptibility index (SSI) and stress tolerance index (STI)) for the seedling traits and GY under pre- and post-anthesis drought stress were calculated, based on a mean trait value obtained under stress and the corresponding trait value under control conditions. The ranking of the genotypes based on TOL and STI from seedling traits was found in most cases to be significantly correlated with the ranking of genotypes based on TOL and STI from GY, respectively
Draft Genome Sequences of Agrobacterium nepotum Strain 39/7(T) and Agrobacterium sp. Strain KFB 330
No full textTumorigenic strains of Agrobacterium spp. are responsible for crown gall disease of numerous plant species. We present here draft genome sequences of nonpathogenic Agrobacterium nepotum strain 39/7(T) (CFBP 7436(T), LMG 26435(T)), isolated from crown gall tumor on Prunus cerasifera, and tumorigenic Agrobacterium sp. strain KFB 330 (CFBP 8308, LMG 28674), isolated from galls on raspberry
Occurrence of Cercospora beticola populations resistant to benzimidazoles and demethylation-inhibiting fungicides in Serbia and their impact on disease management
No full textThe emergence of Cercospora beticola populations that are resistant to benzimidazoles (MBC) and demethylation-inhibiting fungicides (DMI) has been recently reported in Serbia and has resulted in a reduced efficacy of fungicides in controlling Cercospora leaf spot (CLS). Between 2008 and 2011, using a discriminatory concentration method in sugar beet fields in two separate regions of Serbia, we determined that 93.3%-98.6% of collected C. bed cola isolates were resistant to MBCs, whereas 6.2%-42.4% were resistant to DMI fungicides. At the same localities, field trials were conducted to investigate the impact of resistant C. beticola populations on disease management From the MBC group of fungicides, both thiophanate methyl and carbendazim failed to suppress the spread of CLS at both of the tested localities. Between 2008 and 2010, DMI fungicides expressed moderate efficacy at a South Banat locality (79.8%-84.6%) whether they were applied individually (flutriafol, epoxiconazole) or in combination with MBCs (epoxiconazole/carbendazim, thiophanate-methyl/epoxiconazole). The frequency of resistant isolates in these test trials ranged from 6.2% to 10.9%. In 2011, at the same locality, conditions were observed to change in favor of the occurrence of resistant populations, which comprised up to 18.7% of the population, at the expense of DMI efficacy in CLS management At a Srem locality, the frequency of C. beticola isolates that were resistant to DMIs was high during all four years of field testing (30.5%-42.4%), and the efficacy of these fungicides ranged from 48.4% to 68.0%. A combination of DMI and a protective chlorothalonil had a stable, moderate impact on disease management regardless of the frequency of DMI resistance, whereas a combination of the cyproconazole DMI with trifloxystrobin from the strobilurin group of fungicides expressed the highest efficacy. High correlation coefficient values (r = 0.87) indicated how strongly the frequencies of resistant populations affected disease severity in the trial plots that were treated with carbendazim and thiophanate methyl, as well as in the plots that were treated with flutriafol and epoxiconazole (r = 0.98). In shift sensitivity trials, MBC-resistant C. beticola isolates were found at equally high frequencies both before and after the treatments, indicating a complete loss of efficacy in CLS control. This test revealed the significant impact of multiple DMI applications in terms of increasing the frequency of resistant C. beticola populations following treatments with flutriafol, epoxiconazole, epoxiconazole/carbendazim, thiophanate-methyl/epoxiconazole and flutriafol/chlorothalonil, except when used in combination with trifloxystrobin, in which case CLS suppression was substantially high. (C) 2015 Elsevier Ltd. All rights reserved
Parasitism of Trombidium brevimanum larvae on agrobiont linyphiid spiders from Germany
No full textAn experiment on three differently-managed agricultural fields in Ahlum, Germany, which aimed at establishing the impact of different management systems on the biodiversity of predators and decomposers, yielded a significant number of spiders parasitized by larvae of Trombidium brevimanum (Actinotrichida, Parasitengona, Trombidiidae). Spider data from the whole sampling period (September 2010-July 2012), indicated that ectoparasitic larvae were recorded only on spiders in pitfall traps in the period of June-July 2011. In this period, only eight species of Linyphiidae-out of 42 species assigned to nine spider families recorded from the study area-were parasitized by mites; considerable levels of parasitism were recorded on Erigone atra, E. dentipalpis, and Oedothorax apicatus. The highest prevalence of parasitism was recorded on the organic field for E. atra (29 %), while on the integrated and conventional fields significantly fewer parasitized spiders were observed. The preferred attachment sites on the spider host were regions with softer cuticle, especially regions on the carapace and on the abdomen, adjacent to the pedicel
The First Report of Macrophomina phaseolina of Immortelle (Helichrysum italicum) in Serbia.
No full textNano-morfologija Laimaphelenchus belgradiensis (Nematoda: Aphelenchoididae) i ključ za vrste roda Laimaphelenchus
No full textLaimaphelenchus are very small nematodes, some parts of their body are measured in nanometers. In the past, the only way of identification and classification of these organisms were morphology based on anatomy and measurements. Nowadays, this approach is appended with nano-morphology with the help of scanning electron microscopy which reveal unknown morphological details facilitating the taxonomy work. A new species of the genus Laimaphelenchus is recently described. Laimaphelenchus belgradiensis is discovered on a black pine showing symptoms similar to those caused by Bursaphelenchus xylophilus. Although both species belong to the same family and are similar in morphological sense, females of both species have the vulval flap and males have similar spicules, they possess significant differences. The main morphological difference is the presence of supplementary tail organs-tubercles with finger-like protrusions, visible only with scanning electron microscope. The role of the protrusions is explained and a key to species of the genus Laimaphelenchus is given in this paper.Laimaphelenchus vrste su veoma sitne nematode, tako da se neki delovi njihovog tela mere nanometrima. Morfologija bazirana na anatomskim karakteristikama i merenjima pomoću optičkog mikroskopa je u prošlosti bila jedini način identifikacije i klasifikacije ovih organizama. U današnje vreme ovaj pristup je dopunjen nano-morfologijom uz pomoć scanning elektronske mikroskopije, kada se otkrivaju nepoznati morfološki detalji koji olakšavaju rad taksonomima. Nova vrsta roda Laimaphelenchus je skoro opisana. Laimaphelenchus belgradiensis je otkriven na crnom boru sa simptomima sličnim onima koje izaziva Bursaphelenchus xylophilus. Iako obe vrste pripadaju istoj familiji i slične su u morfološkom pogledu, ženke obe vrste poseduju vulvalni poklopac, i spikuli mužjaka su slični, one poseduju i značajne razlike. Osnovna morfološka karakteristika koja ih razlikuje je prisustvo pomoćnih organa na repu - tuberkula sa prstolikim proširenjima vidljivih samo uz pomoć scanning elektronskog mikroskopa. Uloga ovih tvorevina je u radu objašnjena i ključ za vrste je dat u ovom radu
Genetic and morphological variation in sexual and asexual parasitoids of the genus Lysiphlebus - an apparent link between wing shape and reproductive mode
No full textBackground: Morphological divergence often increases with phylogenetic distance, thus making morphology taxonomically informative. However, transitions to asexual reproduction may complicate this relationship because asexual lineages capture and freeze parts of the phenotypic variation of the sexual populations from which they derive. Parasitoid wasps belonging to the genus Lysiphlebus Foerster (Hymenoptera: Braconidae: Aphidiinae) are composed of over 20 species that exploit over a hundred species of aphid hosts, including many important agricultural pests. Within Lysiphlebus, two genetically and morphologically well- defined species groups are recognised: the "fabarum" and the "testaceipes" groups. Yet within each group, sexual as well as asexual lineages occur, and in L. fabarum different morphs of unknown origin and status have been recognised. In this study, we selected a broad sample of specimens from the genus Lysiphlebus to explore the relationship between genetic divergence, reproductive mode and morphological variation in wing size and shape (quantified by geometric morphometrics). Results: The analyses of mitochondrial and nuclear gene sequences revealed a clear separation between the "testaceipes" and "fabarum" groups of Lysiphlebus, as well as three well-defined phylogenetic lineages within the "fabarum" species group and two lineages within the "testaceipes" group. Divergence in wing shape was concordant with the deep split between the "testaceipes" and "fabarum" species groups, but within groups no clear association between genetic divergence and wing shape variation was observed. On the other hand, we found significant and consistent differences in the shape of the wing between sexual and asexual lineages, even when they were closely related. Conclusions: Mapping wing shape data onto an independently derived molecular phylogeny of Lysiphlebus revealed an association between genetic and morphological divergence only for the deepest phylogenetic split. In more recently diverged taxa, much of the variation in wing shape was explained by differences between sexual and asexual lineages, suggesting a mechanistic link between wing shape and reproductive mode in these parasitoid wasps