Risikofolgeabschätzung für den Einsatz mikrobieller Antagonisten: Gibt es Effekte auf Nichtzielorganismen?

Biological control of phytopathogenic fungi using antagonistic microorganisms is an environmentally friendly alternative in plant protection. However, possible non-target effects of the applied antagonists on ecologically important soil-microbes need to be considered. Therefore, the aim of this study was to analyse the effect of biological control agents (BCAs) on non-target microbes in the field. Whereas the bacterial BCAs Serratia plymuthica HRO-C48 and Streptomyces sp. HRO-71 were applied to control the pathogen Verticillium dahliae on strawberry and potato, the bacterial strains Pseudomonas trivialis 3Re2-7, P. fluorescens L13-6-12, S. plymuthica 3Re4-18 and the fungal antagonists Trichoderma reesei G1/8 and T. viride G3/2 were introduced to control Rhizoctonia solani on lettuce and potato. As the analysed BCAs belong to different microbial groups like grampositive (HRO-71) and gramnegative (HRO-C48, L13-6-12, 3Re2-7, 3Re4-18) bacteria or the ascomycota (G1/8, G3/2) and originated from different micro-habitats like the rhizosphere or the endorhiza, general conclusion could be drawn from our results. After BCA treatment we did not observe any long-term effect on the plant-associated microbes in any tested pathosystem. Therefore, no sustainable risks could be seen for the indigenous micro-organisms. Our new findings may help to improve the development as well as the registration procedures of future microbial plant protection products.     

Tracing a 14C-labeled carbamate molluscicide through the digestive system of deroceras reticulatum (müller)

The passage of a ¹⁴C-labeled carbamate, 2-(2-chloro-1-methoxy-' ethoxy)phenyl N-methylcarbamate, or its labeled metabolites through the alimentary system of the grey garden slug Deroceras reticulatum was examined by autoradiographic studies and scintillation counting. It was demonstrated that, in a first step, the molluscicide penetrated the cells of the oesophagus and the crop. It was quickly transported by the hemolymph to the periphery of the body and re-entered the cells of the digestive tract and the mid-gut gland in a second step from the hemolymph side. The crypt cells of the mid-gut gland are discussed as cells involved in detoxification, and connective tissue cells as the major storage sites of the labeled material. Excretion in feces and secretion in mucus are thought to be the routes of ¹⁴C elimination.     

New sources of resistance to Meloidogyne incognita race 3 in wild cotton accessions and histological characterization of the defence mechanisms

Accessions of Gossypium spp., some of them never previously tested, were evaluated for resistance to a local isolate of Meloidogyne incognita race 3 in greenhouse experiments. Nematode infection was characterized based on the galling and egg mass indexes and the reproduction factors (RF). Root‐knot nematode reproduction among the newly tested accessions varied from highly susceptible (AS0188, AS0189) to moderately resistant (MT123 no. 3), and some accessions showed highly reduced nematode reproduction (CIR1343, CIR1348, Fai Mui). Histological observations of two resistant accessions (G. barbadense CIR1348 and G. hirsutum TX‐25, respectively) showed that resistance occurs through a two‐stage mechanism in the first accession and through a single‐stage mechanism in the second. Parasitism is blocked early after second‐stage juvenile (J2) penetration or during its initial tissue migration (CIR1348) and the development of later‐stage juveniles into female adults is suppressed at a later stage (TX‐25 and CIR1348). Fluorescence and bright light microscopy showed that root cells surrounding nematodes exhibit a hypersensitivity‐like reaction, with the accumulation of presumably phenolic compounds and the presence of necrotic cells that limit the development of nematodes and the formation of giant cells. Underdeveloped giant cells with degenerated cytoplasmic content were found in small numbers in CIR1348 and in large numbers in TX‐25, along with deformed nematodes. The full characterization of the defence mechanisms of novel sources of resistance to the root‐knot nematode in cotton constitutes a first step towards their use in crop improvement.     

Improved vitellogenesis,gonad development and egg diameter in catfish (Pangasianodon hypophthalmus) supplemented with turmeric (Curcuma longa) powder

An experiment was conducted to study the effect of supplementing catfish (Pangasianodon hypophthalmus) with turmeric (Curcuma longa) on the vitellogenic capacity of the liver as a new method to improve reproductive performance in oviparous animals. The experimental catfish were assigned to a completely randomized design consisting of four doses of supplemental turmeric (0, 1.2, 2.4 and 4.8 g/kg feed) with 10 catfish with body weights ranging from 2 to 4 kg in each group. Blood samples were collected on days 0, 14, 28, 42 and 56 of turmeric supplementation to measure the concentrations of plasma oestradiol‐17ß and vitellogenin. The weights of the body, gonads and liver were measured on days 0, 28 and 56. The fecundities of the catfish were measured on days 28 and 56 of turmeric supplementation, and egg diameters were measured on days 28 and 42. The results showed that catfish supplemented with turmeric at a dose of 2.4 or 4.8 g/kg feed had higher growth rates, higher plasma oestradiol‐17β and vitellogenin concentrations, and higher gonad somatic index values and egg diameters. This is the first report demonstrating that the hepatoprotective activity of the curcumin in turmeric could be used to improve both vitellogenin synthesis, which improves nutrient deposition in the ovulating eggs, and the reproductive performance of teleost fish and oviparous animals.