High pressure liquid chromatographic determination of vitamin D3 in livestock feed supplements.

Vitamin D3 is determined in livestock feed supplements by high pressure liquid chromatography (HPLC). Extracts of the samples are quantitated using normal phase chromatography. If interfering co-extractives are present, an aliquot of the extract is injected on the normal phase column, and the fraction corresponding to vitamin D3 is collected. The vitamin fraction is then further cleaned up and separated from interferences by reverse phase chromatography, and quantitated by measuring the ultraviolet absorption at 254 and 280 nm. The method measures actual vitamin D3 content in the presence of pre-vitamin D, tachysterol, isotachysterol, and vitamin A.     

Marine Microbial-Derived Resource Exploration: Uncovering the Hidden Potential of Marine Carotenoids

Microbes in marine ecosystems are known to produce secondary metabolites. One of which are carotenoids, which have numerous industrial applications, hence their demand will continue to grow. This review highlights the recent research on natural carotenoids produced by marine microorganisms. We discuss the most recent screening approaches for discovering carotenoids, using in vitro methods such as culture-dependent and culture-independent screening, as well as in silico methods, using secondary metabolite Biosynthetic Gene Clusters (smBGCs), which involves the use of various rule-based and machine-learning-based bioinformatics tools. Following that, various carotenoids are addressed, along with their biological activities and metabolic processes involved in carotenoids biosynthesis. Finally, we cover the application of carotenoids in health and pharmaceutical industries, current carotenoids production system, and potential use of synthetic biology in carotenoids production.     

Scheduling irrigations by merging water-use and radar backscatter models

Penman-Monteith methods were merged with the water cloud radar model to simulate soil moisture, canopy moisture and radar backscatter for a field of potatoes (Solanum tuberosum) in the United Kingdom. The objective of this paper is to present the irrigation scheduling potential of the merged model. This study simulates water-use: radar backscatter simulation results are presented elsewhere and yield is not calculated by the merged model. Soil moisture deficit switches control the model, which in turn uses predetermined application rates defined by the user. The simulation results show that the most effective irrigation application during the 1999 simulation period would utilise 25 mm of water when a soil moisture deficit of 30 mm is reached. Significantly, this would have required less water application than that actually applied to the field.     

Genetics of stem elongation ability in rice (Oryza sativa L.)

Summary The genetics of stem elongation ability in rice was studied in parents, F₁, F₂ and backcross generations of six crosses. Segregation analysis indicated dominance for stem elongation ability. Estimation of genetic parameters under epistatic model indicated more than one locus control stem elongation ability and both additive and nonadditive gene effects were important. Epistatic effects were predominant over additive and dominance effects with an important role of duplicate type of epistasis. The occurrence of significant additive and additive x additive types of genetic variation and the moderately high broad sense heritability indicated the possibility of selection for an increased manifestation of stem elongation ability.     

The importance of economic injury levels in the development of integrated pest control programs

Summary Although economic injury levels have long been considered of importance in determining the needs for pest control measures, they take on added significance in integrated pest control programs. The designation of damage tolerance levels defines the goals of the integrated control effort. These management goals should be defined in terms of damage not numbers of pests. Although insect numbers and damage incidence are related they are not perfectly correlated and the relationship varies with changes in the ecological and economic environment. Many plants have the ability to tolerate or compensate for large amounts of injury without affecting yield or quality. Other plants have a limited capacity to produce a marketable crop; pest injury which does not reduce the capacity of the plant is not damage. These characteristics of plants, among others, and the limitations of artificial control measures permit the maintenance of subeconomic levels of pests in agricultural crop areas. These subeconomic pest populations foster an entomophagous fauna. It is very difficult to calculate precise cost/potential benefit ratios because of subtile long-term effects of artificial controls and the vagaries of estimates of potential economic value of the harvested crop.

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Zusammenfassung Obwohl man die wirtschaftlichen Schadensgrenzen für die Feststellung der erforderlichen Schädlingsbekämpfungsmaßnahmen seit langem für wichtig hält, gewinnen sie in integrierten Programmen zusätzliche Bedeutung. Die Bestimmung der Schadenstoleranzgrenzen setzt die Ziele für den integrierten Bekämpfungseinsatz. Die Art der Behandlung sollte auf Grund des Schadens und nicht auf Grund der Zahl der Schädlinge festgelegt werden. Die Insektenzahl und die Häufigkeit des auftretenden Schadens stehen zwar miteinander im Zusammenhang, sind aber nicht vollständig korreliert. Ihr Verhältnis variiert mit Veränderungen der ökologischen und wirtschaftlichen Situation. Viele Pflanzen haben die Fähigkeit, großen Schaden zu ertragen oder zu kompensieren, ohne daß dadurch der Ertrag oder die Qualität beeinflußt werden. Andere Pflanzen besitzen eine begrenzte Fähigkeit, eine marktgerechte Ernte hervorzubringen. Ein Schädlingsbefall, der die Ertragsfähigkeit der Pflanze nicht beeinträchtigt, ist keine Schädigung. Diese und andere Merkmale der Pflanzen und die Einschränkung der künstlichen Bekämpfungsmaßnahmen gestatten die Erstellung subökonomischer Schadensgrenzen in landwirtschaftlichen Anbaugebieten. Diese subökonomischen Schädlingspopulationen sind in der Lage, eine entomophage Fauna zu fördern. Es ist sehr schwierig, ein genaues Verhältnis zwischen den exakten Kosten und dem potentiellen Nutzen zu berechnen, weil die subtile langfristige Wirkung der künstlichen Bekämpfung und die Zufälligkeiten bei Berechnungen des potentiellen wirtschaftlichen Wertes der Ernte berücksichtigt werden müssen.

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Résumé Bien que le niveau de dégâts économiques ait depuis longtemps été d'une grande importance pour déterminer quelles étaient les mesures de lutte antiparasitaires à prendre, il joue un rôle encore plus significatif dans l'élaboration de programmes de lutte intégrée. C'est la fixation du niveau de dégâts admissible qui établit les buts des efforts à fournir en matière de lutte intégrée. Ces buts devraient être définis en termes de dommages et non de nombres de parasites. Bien qu'il y ait une relation entre le nombre d'insectes et les dommages causés, la corrélation n'est pas parfaite et les rapports varient avec les changements du milieu écologique et économique. Beaucoup de plantes sont capables de tolérer ou de compenser une grande partie des dommages subis sans que le rendement ni la qualité ne s'en trouvent affectés. D'autres plantes au contraire ont une capacité limitée de produire une récolte susceptible d'être commercialisée; du moment que les insectes ne réduisent pas la capacité de production de la plante, on ne peut pas parler de dégâts. Ces caractéristiques que possèdent, entre autres, les plantes et la restriction des mesures de lutte phytosanitaire ont pour résultat le maintien des parasites infestant les récoltes agricoles à des niveaux qui ne menacent pas le rendement, et qui nourrissent la faune insectivore. Il est très difficile de calculer les rapports précis qui existent entre le prix de revient et le bénéfice possible étant donné les effets à long terme non tangibles d'une lutte artificielle et les difficultés à évaluer exactement la valeur virtuelle des récoltes.

     

Susceptibility of potato varieties and advanced breeding lines (Solanum tuberosum L.) toPhytophthora infestans (Mont.) de Bary in greenhouse screenings

Late blight (Phytophthora infestons (Mont.) de Bary) has re-emerged as an important pathogen of the cultivated potato (Solanum tuberosum subsp.tubero-sum L.) in North America. The purpose of this study was to evaluate the relative susceptibility of potato germplasm in the greenhouse in order to initiate a breeding program for resistance to the US-8/A2 mating type which is the more aggressive and prevalent strain of late blight. Whole plants of 147 cultivars and breeding lines were evaluated. Percent plant area infection was visually assessed. Seven days after inoculation, infection ranged from 0 to 100% and the overall mean was greater than 50%. Two-thirds of the cultivars and breeding lines tested were very susceptible to the US-8 genotype. The highest resistance was identified in the somatic hybrids betweenS. tuberosum andS. bulbocastanum and their backcross derivatives. Pike and Snowden were less susceptible than the other North American cultivars. Zarevo was most resistant among the European cultivars. Seven of the advanced breeding lines were equivalent to Zarevo in infection levels. The host plant resistance identified among the material tested in this study can be used by breeding programs to develop improved cultivars with resistance to US-8 genotypes of late blight.