Pharmacological properties of presynaptic muscarinic receptors in the sixth abdominal ganglion of the cockroach,Periplaneta americana L.

The effects of muscarinic agonists on acetylcholine (ACh) release in the cercal-afferent giant-interneuron synapses of the cockroach have been studied using the single-fibre oil-gap method. Decrease in amplitude of the cEPSP was induced by pressure ejection of arecoline (ARE), carbachol (CCh) and oxotremorine free base (OXO) within the sixth abdominal (A6) ganglion. This depressive effect was dose-dependent without any effect at the post-synaptic site in the range of concentrations used. The concentration for 50% of cEPSP inhibition of the most commonly used muscarinic agonists was determined. The rank order of potencies was: ARE > CCh > OXO > McN-A-343 > bethanechol (BET). Plateau levels of 56%, 54% and 68% were reached when increasing the concentration of ARE, CCh and OXO respectively. McN-A-343 and BET had an inhibitory effect on ACh release but higher doses also acted at the postsynaptic level. Furthermore, muscarinic agonists were able to evoke uIPSP and a smaller inhibitory effect of ARE and OXO was observed in presence of picrotoxin. It is concluded that the ACh release in the cockroach A6 ganglion is modulated by presynaptic muscarinic receptors which are possible target sites for insecticides. The presence of putative muscarinic receptors on inhibitory GABAergic interneurons, involved in pre- and postsynaptic inhibition is suspected.     

Effects of green manure and coral lime on corn growth and chemical properties of an acid Oxisol in Western Samoa

Effects of local green manure (GM) and lime on soil productivity in a low-input agricultural system were evaluated by growing three successive crops of sweet corn (Zea mays) on an acid Oxisol (Typic acrorthox, Togitogiga series) in Western Samoa. The soil was amended with coral lime at 0, 5, and 10Mgha^–1 and with cowpea GM at 0, 7.5, and 15Mgha^–1. Commercial NPK fertilizers at 50kgha^–1 each of N, P, and K were included for comparison. The amendments were applied only once prior to planting of the first crop. Response parameters measured included nutrient composition of leaves at tasseling and grain yield of each crop, and selected soil chemical properties at each planting. Yields of the first crop were nearly tripled with GM additions and doubled with lime additions. Such yield increases were caused mainly by better K nutrition and to a lesser extent by enhanced P nutrition. Yields of subsequent crops were much lower than those of the first, and the declines were much steeper for the GM treatments than for the lime treatments. Thus, the enhancement effect on K nutrition did not last beyond one crop. Poor growth of the second and third crops was caused by K deficiency; probably coupled with Mn toxicity. Significant yield reductions were found when Mn-to-K ratios in leaves exceeded 0.010. As for effects on soil, soil pH was increased significantly by lime but only slightly by GM. Given the variable charge property of this Oxisol, each unit pH increase corresponds to a cation exchange capacity (CEC) increase of 5cmol_ckg^–1. Having greater CEC, the amended soil retained K more effectively, thereby causing yield increases, especially of the first corn crop, which required at least 0.75cmol_ckg^–1 of exchangeable soil K or 7% of CEC for adequate growth. Received: 15 April 1996     

Extended summaries physicochemical and biophysical panel symposium neuropeptides

The following are summaries of papers presented at a meeting of the Physicochemical and Biophysical Panel of the Pesticides Group held on 8 December 1987 at the Society of Chemical Industry, 14 Belgrave Square, London SW1X 8PS. The papers published here are entirely the responsibility of the authors and do not reflect the views of the Editorial Board of Pesticide Science.     

Liming Potential of Composts Applied To an Acid Oxisol in Burundi

The adverse effect of soil acidity on plant growth and yield, and the scarcity of commercial agricultural lime (CaCO₃) in Burundi necessitated a search for alternative liming materials. Thus, the liming potential of locally made composts was evaluated in a greenhouse experiment, using an acid Oxisol with sorghum (Sorghum vulgaris) as a test plant. Application rates were 10 g/kg (approximately 20 ton/ha) for the composts and 0, 0.85 and 1.70 g/kg for Verrundi lime. Results showed that the application of lime increased plant growth by reducing exchangeable Al, and by increasing soil pH and available P. So did the composts, which were more effective in correcting soil acidity when they were fresh and enriched with some nutrients during the composting process. Apparently, organic molecules produced by the composts helped to chelate and/or precipitate Al, making the soil more suitable for plant growth. Specifically, an application of 20 ton/ha of composts was equivalent to 0.6 - 1.7 ton CaCO₃/ha, depending on the compost quality.     

Effect of adaptation strategies when feeding fresh cassava foliage on intake and physiological responses of lambs

The objective of the experiment was to study different adaptation strategies to avoid HCN intoxication when feeding fresh cassava foliage to sheep. Twenty-four Phan Rang lambs (initial weight = 19.6 kg at 5.5 months of age) were used in the study. The four experimental diets contained guinea grass (Panicum maximum) supplemented with concentrate at 1.5% of body weight (BW) as dry matter (DM) (control) or supplemented with fresh cassava foliage (FCF) that was introduced into the diet with an adaptation period of 0 (FCF-0), 7 (FCF-7) or 21 (FCF-21) days before reaching the target feeding level of 2% of BW. The average intake of FCF expressed as DM was not different amongst the supplemented treatments and ranged from 1.4 to 1.5% of BW but gradually increased during the first 7 days without any adaptation. The hydrogen cyanide consumed varied from 5.1 to 5.4 mg/kg BW and no difference between treatments with cassava foliage in the diet was found. The live weight gain was significantly higher in the treatments control and FCF-7 compared to FCF-21. No significant differences in heart rate, respiration rate and rumen movement were found between diets. The thiocyanate concentration in the urine of the lambs increased concomitantly with the increase in fresh cassava foliage offered during the first part of the experiment. In conclusion, an adaptation period of approximately 7 days seems to be favourable in combined diets where cassava foliage is offered in quantities up to 2% of BW. This level of intake could enhance the intake and LWG of the lambs without any documented effects on heart rate, respiration rate or rumen movements.     

Marker-Assisted Selection of Xa21 Conferring Resistance to Bacterial Leaf Blight in indica Rice Cultivar LT2

Bacterial leaf blight of rice (BLB), caused by Xanthomonas oryzae pv. oryzae, is one of the most destructive diseases in Asian rice fields. A high-quality rice variety, LT2, was used as the recipient parent. IRBB21, which carries the Xa21 gene, was used as the donor parent. The resistance gene Xa21 was introduced into LT2 by marker-assisted backcrossing. Three Xoo races were used to inoculate the improved lines following the clipping method. Eleven BC₃F₃ lines carrying Xa21 were obtained based on molecular markers and agronomic performance. The 11 lines were then inoculated with the three Xoo races. All the 11 improved lines showed better resistance to BLB than the recipient parent LT2. Based on the level of resistance to BLB and their agronomic performance, five lines (BC₃F₃ 5.1.5.1, BC₃F₃ 5.1.5.12, BC₃F₃ 8.5.6.44, BC₃F₃ 9.5.4.1 and BC₃F₃ 9.5.4.23) were selected as the most promising for commercial release. These improved lines could contribute to rice production in terms of food security.     

Identification of a target‐site mutation conferring resistance to triazine herbicides in oriental mustard (Sisymbrium orientale L.) from Australia

In southern Australia, oriental mustard (Sisymbrium orientale) has been controlled successfully by triazine herbicides for several decades. The screening of 40 populations that were collected from the southern grain belt of Australia during 2010 and 2013 for resistance to six different herbicides (glyphosate, diflufenican, imazamox, chlorsulfuron, atrazine and 2,4‐dichlorophenoxyacetic acid) identified two oriental mustard populations as highly resistant to atrazine. Compared to the known oriental mustard‐susceptible populations (S1 and S2), these two resistant populations (P17 and P18) from near Horsham, Victoria, Australia, were 311‐ and 315‐fold resistant to atrazine, as determined by a comparison of the LD₅₀ values. However, there was no resistance to diuron detected in these populations. Sequencing of the chloroplast psbA gene identified a missense mutation of serine 264 to glycine in both herbicide‐resistant oriental mustard populations, which is known to confer high‐level atrazine resistance in other species.     

麻疹病毒核衣壳蛋白分子生物学及其应用的研究进展

麻疹病毒属(Morbillivirus)的病毒是一类重要的人和动物致病性病原.其中包括牛瘟病毒(Rinderpest virus,RPV)、小反刍兽疫病毒(Peste des Petits Ruminants virus,PPRV)、犬瘟热病毒(Canine Distemper vires,CDV)和麻疹病毒(Measles virus,MV)[1].     

施肥技术对稻米产量与品质的影响

除品种本身外,栽培技术尤其是施肥技术正以一种不容忽视的力量影响着稻米品质。通过不同施肥量、不同施肥方法等试验研究表明:增施氮肥,能有效提高稻米蛋白质含量,在施肥水平相同情况下,分次施用氮肥,其稻米的蛋白质含量高于一次性施用,生育期间均匀施氮的蛋白质含量显著高于两促施氮法,特别是穗肥追施氮肥时提高稻米蛋白质含量和降低直链淀粉含量效果最佳,从而提高稻米品质。