The integrated concept of disease resistance; a new view including horizontal and vertical resistance in plants

Horizontal, uniform, race-non-specific or stable resistance can be discerned according to Van der Plank, from vertical, differential, race-specific or unstable resistance by a test in which a number of host genotypes (cultivars or clones) are tested against a number of pathogen genetypes traces of isolatest. If the total non-environmental variance in levels of resistance is due to main effects only differences between cultivars and differences between isolates) the resistance and the pathogen many (in the broad sense) are horizontal in nature. Vertical resistance and pathogenicity are characterized by the interaction between host and pathogen showing up as a variance compenent in this test due to interaction between cultivars and isolates. A host and pathogen model was made in which resistance and pathogenicity are governed by live polygenic loci. Within the host the resistance genes show additivity. Two models were investigated in model I resistance and pathogenicity genes operate in an additive way as envisaged by Van der Plank in his horizontal resistance. Model II is characterized by a gene-for-gene action between the polygenes of the host and those of the pathogen. The cultivar isolate test in model I showed only main effect variance. Surprisingly, the variance in model II was also largely due to main effects. The contribution of the interaction to the variance uppeared so small, that it would be difficult to discern it from a normal error variance. So-called horizontal resistance can therefore be explained by a polygenic resistance, where the individual genes are vertical and operating on a gene-for-gene basis with virulence genes in the pathogen. The data reported so far support the idea that model II rather than model I is the realistic one. The two models also revealed that populations with a polygenic resistance based on the gene-for-gene action have an increased level of resistance compared with the addition model, while its stability as far as mutability of the pathogen is concerned, is higher compared to those with an additive gene action. Mathematical studies of Mode too support the gene-for-gene concept. The operation of all resistance and virulence genes in a natural population is therefore seen as one integrated system. All genes for true resistance in the host population, whether they are major or minor genes are considered to interact in a gene-for-gene way with virulence genes either major or minor, in the pathogen population. The models revealed other important aspects. Populations with a polygenic resistance based on a gene-for-gene action have an increased level of resistance compared to populations following the addition model. The stability, as far as mutability of the pathogen is concerned, is higher in the interaction model than in the addition model. The effect of a resistance gene on the level of resistance of the population consists of its effect on a single plant times its gene frequency in the population. Due to the adaptive forces in both the host and the pathogen population and the gene-for-gene nature of the gene action an equilibrium develops that allows all resistance genes to remain effective although their corresponding virulence genes are present. The frequencies of the resistance and virulence genes are such that the effective frequencies of resistance genes tend to be negatively related to the magnitude of the gene effect. This explains why major genes often occur at low frequencies, while minor genes appear to be frequent. It is in this way that the host and the pathogen, both as extremely variable and vigorous populations, can co-exist. Horizontal and vertical resistance as meant by Van der Plank therefore do not represent different kinds of resistances, they represent merely polygenic and oligogenic resistances resp. In both situations the individual host genes interact specifically with virulence genes in the pathogen. Van der Plank's test for horizontal resistance appears to be a simple and sound way to test for polygenic inheritance of resistance. The practical considerations have been discussed. The agro-ecosystems should be made as diverse as possible. Multilines, polygenic resistance, tolerance, gene deployment and other measures should be employed, if possible in combination

Pulsed PECVD growth of silicon nanowires on various substrates

Silicon nanowires with high aspect ratio were grown using PPECVD and a gold catalyst on a variety of different substrates. The morphology of the nanowires was investigated for a range of crystalline silicon, glass, metal, ITO coated and amorphous silicon coated glass substrates. Deposition of the nanowires was carried out in a parallel plate PECVD chamber modified for PPECVD using a 1kHz square wave to modulate the 13.56MHz RF signal. Samples were analyzed using either a Phillips XL20 SEM of a ZEISS 1555 VP FESEM. The average diameter of the nanowires was found to be independent of the substrate used. The silicon nanowires would grow on all of the substrates tested, however the density varied greatly. It was found that nanowires grew with higher density on the ITO coated glass substrates rather than the uncoated glass substrates. Aligned nanowire growth was observed on polished copper substrates. Of all the substrates trialed, ITO coated aluminosilicate glass proved to be the most effective substrate for the growth of silicon nanowires

Improving profit in the flower growing business

Flower growing is a business. It can be a very profitable business. Just as in any enterprise the success depends very much on the knowledge, skill, tools and business acumen the owner brings to the operation. All small businesses face similar hurdles to achieving success. A small proportion grow and become highly profitable, the bulk allow the owner operator to make a living but unfortunately a percentage of enterprises fold up after a relatively short time or are maintained in a sub profitable form. This bulletin will provide some experiences, tools, suggestions for new flower businesses and for those that exist in the industry but at a level not appropriate to their expectations

Fiction for Peace?:Domestic Identity, National Othering and Peace Education in Dutch Historical Novels for Children, 1914-1935

Historical fiction for children has long functioned as a continuation of history education. World War I brought about critique on history education in several Western European countries. The nationalistic and chauvinistic representation of historical events was claimed to have contributed to the outbreak of war. In the educational discourse a discussion arose about changing history education into peace education. In this article the impact of this discussion on historical novels for children is investigated. Dutch historical novels for children serve as a case study. The novels are contextualised within the educational debate from the perspective of imagology. Representations of the own identity and national others are analysed, supplemented with an analysis of references to war and peace. The article shows how historical fiction for children held on to the glorification of nationality for a long time, but joined the educational discourse by occasionally framing the represented battles in the spirit of peace education

Oude verhalen voor jonge lezers:Over bewerkingen van literaire klassiekers

Het hertalen en bewerken van literaire meesterwerken is een oude traditie. Zo wordt het literaire erfgoed doorgegeven aan volgende generaties. De redenen die hedendaagse hertalers geven voor het bewerken van klassieke teksten komen overeen met de redenen die daar meer dan een eeuw geleden voor werden gegeven. Veel gebruikte bewerkingsstrategieën zijn moderniseren en inkorten. Op deze manier wordt in bewerkingen die zijn bedoeld voor jonge lezers rekening gehouden met hun lees- en levenservaring en hun leef- en belevingswereld, maar ook met de opvattingen van volwassenen over wat goed en geschikt is voor jonge lezers. Om te laten zien dat zij aan die opvattingen tegemoet kwamen, plachten bewerkers in bewerkingen van internationale klassiekers, zoals Reynaert de Vos, Tijl Uilenspiegel, Robinson Crusoe en Gulliver’s travels, tussen 1850 en 1950 via intertekstuele ‘onderonsjes’ over de hoofden van de kinderen heen te knipogen naar volwassen meelezers

1976 Sunflower-safflower irrigated variety trial 1976-1977

In 1975/76 two varieties of sunflower, Hysun 10 and Hysun 20, as well as Safflower (Gila) were grown in a large alternative crop demonstration. Results were sufficiently good to warrant more and closer examination. This led to the present variety trial using varieties suggested by Mr. M. Poole. The aim was to evaluate six sunflower varieties and one safflower. The work was carried out in the light of reduced profitability of peas, beans and some fruit crops. This results in a number of growers having irrigation water and equipment under-employed. Other farmers are after a crop which will give them a decent profit. If high yields can be obtained consistently, sunflowers may provide an opportunity for farmers to make additional income. Results Sunflower & Safflower Variety trial. 1976/77. Mr. K. Rutter economist at the Bunbury office assisted with the economic assessment. He in turn was assisted by Mr. J. Middlemas in calculating the irrigation costs. Mr. M. Poole provided seed supplies and general suggestions on the trial he also arranged oil content analysis. R. Ramm, R. Trigwell for harvesting the plots and the Manjimup Research Station staff for looking after the crop. Reference:- F.P.C. Blarney. Boron Nutrition of Sunflower(Helianthus annuus L.) on an Avalon medium sandy loam. Agrochemophysica 8, 5-10 1976