Sexual compatibility types of Bremia lactucae isolates originating from Lactuca serriola

Results are given on the occurrence of sexual compatibility types of seven isolates ofBremia lactucae originating fromLactuca serriola (prickly lettuce). It is concluded that the isolates studied are heterothallic. Both compatibility types (B1 en B2) were determined, but type B2 was prevalent. Sexual recombination ofB. lactucae isolates originating from wild and cultivated lettuce may occur.Samenvatting Zeven isolaten vanBremia lactucae, afkomstig vanLactuca serriola in Tsjechoslowakije, zijn onderzocht op hun sexuele compatibiliteitstype door ze te combineren met Nederlandse fysio's vanB. lactucae, afkomstig van cultuursla (L. sativa), waarvan het compatibiliteitstype (B1 of B2) bekend is. Alle isolaten vanL. serriola bleken heterothallisch te zijn, waarbij type B2 meer werd aangetroffen dan type B1. Sexuele recombinatie vanBremia-isolaten van wildeLactuca-soorten en cultuursla blijkt goed mogelijk te zijn.     

Concepts and Direction of Induced Systemic Resistance in Plants and its Application

Resistance to plant disease is often specific and metabolites and receptors contributing to this specificity may have specific structures. However, simple, structurally-unrelated compounds induce systemic resistance in unrelated plants to diverse pathogens including fungi, bacteria and viruses. Both resistance and induced systemic resistance (ISR) are associated with the rapid accumulation of the same structurally unrelated putative defense compounds that have diverse functions. It has been suggested that cultivar (race)-specific resistance is initiated by the specific interaction of a pathogen product (or pathogen induced product) and a plant receptor. However, restricted infection by pathogens can result in ISR and many different compounds can cause ISR. It is thus evident that there are both specific and non-specific routes to the master switch for ISR and there may be more than one master switch. Are reactive oxygen species and free radicals regulating the master switch(es) via both routes? It is also evident there are many switches, other than the master switch. Adding to the complexity of resistance and ISR are the observations that different compounds and pathways may mediate different biochemical resistances. Activation of one of the pathways may antagonize or enhance the activation or effectiveness of another. The review will address these complexities and questions and propose directions of research which require high priority. Factors which encourage and suppress the application of ISR in agriculture will also be addressed.     

Fate of humic acids isolated from natural humic substances

Composition of humic acids (HA) is a function of plant-derived inputs, degradation processes regulated by microorganisms, organo-mineral interactions and age. Characterization of different origin humic substances is important for evaluation of their contribution to stabile and labile carbon pool in the environment. The relative abundance of chemical components in HA isolated from soils, compost, commercial lignohumates, alginite, acadiane and lignite was studied with aim to quantify content of important biomarkers such as amino acid, lipids and polyphenols. HA were considered as a heterogeneous complex and high concentration of peptides, polyphenols and lipids was determined in acadian-HA to compare with soil-HA. Compost-HA contained much more amino acids to compare with soil-HA samples. Alginite-HA and lignite-HA were similar in biomarkers content to soil-HA. Fourier transform infrared spectroscopy confirmed that chemical composition and functional groups content differs with the origin, humification degree and the age of studied samples. Soil-HA are typically composed of a variety of ?OH, COOH?, C–O, C–H₂, (aliphatic and aromatic) groups, quinines, lignin fragments, polysaccharide, monosaccharide and proteins fragments, which are linked together by ?O?, ?NH?, ?H=, >C=O, metal ions and –S? groups. ¹³C NMR spectroscopy showed that aromatic carbon content was the highest in lignite-HA and soil-HA.     

Residual plant nutrients in crop residues – an important resource

With increasing demand for sustainable production, the need to effectively utilise site-based resources increases. One such resource is the remaining crop residues, both above and below ground, after harvest. In order to assess the magnitude of this resource, this study determined the plant nutrient contribution of residues from 17 different crops in seven different regions of Slovakia over a nine-year period. The soil profile 0.0–0.3?m was taken into account at belowground residues sampling. The results showed that winter rape, mustard, corn maize, triticale, winter rye with straw and sunflower left the most residues, exceeding 8 tons of dry biomass per hectare. Root crops (sugar beet, potatoes) and peas left less than 3 tons of residual dry biomass per hectare. Using these data, the nutrient potential coefficient, i.e. the amount of nutrients left by production of one ton of the main product was calculated by polynomial regression. With these coefficients and the known yield of a given crop, it was possible to calculate how much nitrogen, phosphorus and potassium each crop leaves in the soil after harvest. It was found that the amount of nitrogen left ranged from 20 to 132?kg, phosphorus from 2 to 24?kg and potassium from 13 to 218?kg per hectare. This has to be taken into account when calculating the fertiliser requirement of the subsequent crop in order to achieve better resource utilisation, thereby reducing the risk of eutrophication and improving farm profits by reducing expenditure on fertiliser.     

芨芨草水土保持功能的初步研究

芨芨草是黄土高原地区广泛分布的禾本科植物.人们对其水土保持方面的定量研究基本上还处于空白.通过对芨芨草草地土壤抗冲性、渗透性、土壤抗剪强度等指标的研究,来探讨芨芨草的水土保持功能.结果表明:芨芨草能明显提高土壤的抗冲性、渗透性及土壤的抗剪强度,并能增加地表的覆盖度.芨芨草在黄土高原地区的水土保持工作中有着广阔的应用前景.     

Gill Reaction to Pollutants from the Tamiš River in Three Freshwater Fish Species,Esox lucius L. 1758, Sander lucioperca (L. 1758) and Silurus glanis L. 1758: A Comparative Study

The study evaluated the effects of waterborne pollutants from the Tami? River on gill histology and possible differences in gill reaction patterns between three freshwater fish species, pike Esox lucius L. 1758, pike‐perch Sander lucioperca (L. 1758) and wels catfish Silurus glanis L. 1758 from the Tami? River. Gills from analysed fish species showed moderate to intense histopathological alterations. The most frequent progressive alteration was hyperplasia of epithelium, whereas the most frequent regressive alteration was epithelial lifting. Circulatory disturbances were most often manifested in the form of hyperaemia. During comparative analysis, differences in gill indices, reaction and alteration indices, as well as in gill and filament prevalence between analysed species, were observed. Although all analysed fish species did show both progressive and regressive alterations, there was a significant difference in the level of expression of these reaction patterns. Gill index obtained for pike clearly stands out as the lowest. Wels catfish showed the highest progressive reaction index, significantly higher in comparison with the other two species (P < 0.05), while pike‐perch showed the highest regressive reaction index, also significantly higher in comparison with the other species (P < 0.001). These results may implicate species‐specific gill reactions and thus present a useful tool for better understanding toxic mechanisms of various pollutants.     

Flowering estimation in apple orchards by image analysis

Tree-specific management practice related to individual tree physiological condition is necessary for higher quality and quantity in apple fruit production. Detection of apple flowering abundance based on analysis of HSL (hue, saturation, luminance) images was used to estimate the number of flower clusters (FC) of individual trees in a high density apple orchard. The image acquisition was performed with a still camera and an industrial color camera during the day and night. The FC estimation algorithm included HSL thresholding with parameter optimization. Three hypothetical, tree-specific management practices (sprayings) were assumed, using >25, >50 and >100 FC thresholds to carry out the practice. When an industrial camera was used for image acquisition during the daytime and hypothetical spraying was done by on/off criterion >100 FC per tree, 10 % incorrect executions were identified. Comparable FC counting performance was achieved by using a still camera or an industrial camera.     

RT13型指盘搂草机的设计与研究

针对天然草场产草量低、收集成本高及国外机具价格高这一现状,设计了RT13型指盘搂草机。在介绍搂草机整机结构及工作原理的基础上,对其指盘的运动及指盘平面距离等主要参数进行了设计计算。草场作业试验表明:该搂草机操作简单,形成的草条连续、外形整齐,可有效减少牧草收集时间,从而降低机具燃油消耗及人工成本。该机具各项技术性能指标符合设计要求,满足天然草场的收获要求。     

Soil chemical properties,plant species composition,herbage quality,production and nutrient uptake of an alluvial meadow after 45 years of N,P and K application

Little is known about the long-term effects of mineral N, P and K application on the nutritional status of mown alluvial grasslands. We asked how long-term fertilizer application affected soil chemical properties, plant species composition, herbage production, nutrient concentrations in soils and plants and balance of nutrients. Six treatments (control, PK, N50PK, N100PK, N150PK and N200PK) were investigated at the Černíkovice Experiment (Czech Republic) established in 1966 on an Alopecurus pratensis meadow, using annual application rates of 50, 100, 150 and 200 kg N, 40 kg P and 100 kg K ha⁻¹. Data were collected and analysed for 2007, 2008 and 2009. Although fertilizers had been applied over 45 years, differences in soil chemical properties between fertilization treatments were small. The legumes Lathyrus pratensis and Trifolium repens responded highly positively to PK application, and tall grasses, A. pratensis in particular, to NPK application. Herbage quality was high in terms of content of major nutrients, and its chemical properties varied considerably between treatments, cuts and years. Mean annual herbage yield ranged from 6·1 in the control to 9·7 t ha⁻¹ in the N200PK treatment. Herbage production was N-limited in 2007 and 2009, but not in 2008. Seasonal N agronomical efficiency ranged from 4·2 to 22·9 kg of DM herbage per kg of applied N. The herbage N:P and N:K ratios did not reflect the actual response of herbage production to N application. A negative balance between N applied and N removed in harvested herbage was recorded in all treatments. We concluded that in highly productive alluvial grasslands, mineral-rich soils can respond weakly to N, P and K application, fertilizer application modifies plant species composition and herbage production is not N-limited in all years. Nutrient ratios must be interpreted with caution for the estimation of nutrient limitation.