Genetic relationships of avocado (Persea americana Mill.) using RAPD markers

RAPD (randomly amplified polymorphic DNA) analysis was carried out on 16 accessions representing the three ecological races of avocado (Persea americana Mill.), and one accession of P. schiedeana Nees. Twenty two preselected primers produced 133 polymorphic DNA fragments in the RAPD assay of the avocado accessions. One primer was identified which could differentiate each of the avocado accessions. Potentially race-specific markers for each of the Mexican, Guatemalan, and West Indian races, have been detected. A Jaccard's similarity coefficient matrix was generated and a dendrogram constructed using UPGMA (unweighted pair-group method of arithmetic averages) cluster analysis. Percentage similarity between avocado accessions ranged from 46% to 85%. The lowest similarity (between 22% and 29%) was revealed between P. schiedeana and any P. americana accession. Average similarity within races of avocado was 75% for the Mexican race, 71% for the West Indian race and 73% for the Guatemalan race. Average similarity between races ranged from 53% to 58%. The dendrogram identified three groups, representing the races of avocado. These results are in concordance with the present classification of avocado into three subspecies (varieties) of P. americana, namely drymifolia, americana, and guatemalensis, corresponding to the Mexican, West Indian and Guatemalan races, respectively, and confirm the separate species status of P. schiedeana. We conclude that RAPD markers may be useful for the classification of avocado and for the assessment of genetic diversity of avocado germplasm. This revised version was published online in July 2006 with corrections to the Cover Date.     

Wirkung von Neem-Produkten auf höhere Pflanzen und ihre mögliche Nutzung zur Reduzierung der Seitentriebe von Kulturpflanzen sowie zur Unkrautbekämpfung – eine Bestandsaufnahme

The neem tree (Azadirachta indica A. Juss) offers many possibilities of usage. In plant protection mostly the insecticidal activity of neem products is important. In different parts of the plant several biologically active substances occur. One is the active ingredient azadirachtin, which already is commercially used as an insecticide against insect pests. Some active ingredients of neem may be systemically taken up by the treated plants. Often a rapid decomposition occurred which was enhanced by UV radiation. Therefore formulated neem products often need a UV blocker to elongate their activity. After the application of neem products within plant protection sometimes phytotoxic effects could be observed on different plant species. This phytotoxicity can be used to reduce suckers on tobacco plants and recently also on eucalyptus plants. The existing trials to use neem products for weed control mostly concentrated on the direct treatment of some parasitic weeds like Cuscuta, Orobanche and Striga as well as on a few other weeds (e.g. Echinochloa crus-galli). Mostly the growth of the weeds which were often repeatedly treated with high dosages was reduced, but many plants remained still alive. At present the potential of neem products for an effective weed control is not sufficiently investigated. As a consequence of some already known insecticidal and microbiocidal activities of many neem products also side effects on parts of the epigeic and soil fauna and on the nitrification should be considered after usage for weed control.     

Fire place preferences of forest visitors in northwestern Switzerland: Implications for the management of picnic sites

Some recreational activities in urban forests can cause extensive damage to soil and vegetation. In Switzerland, forest visitors frequently build fires outside picnic sites for barbecuing. This indicates that the existing picnic sites are either not attractive enough for these visitors, or that there are not enough sites for all the visitors during peak days. We used an on-site survey to assess the requirements of picnickers in two forest areas in the vicinity of Basle. Results showed that the existing picnic sites do not meet the requirements of some visitor groups, causing the respective visitors to make their own fires in locations that suit them better. There was a preference for sites near streams, away from forest roads and close to open spaces. Furthermore, while some visitors highly appreciated the well-equipped official sites, others preferred more natural infrastructure with pieces of stones forming a fire ring rather than concrete rims, and logs to sit on instead of benches. Picnic sites that are closer to the requirements of visitors who normally steer away from official sites might reduce the number of self-made fire rings. The study shows that understanding visitor behaviour is a prerequisite for the implementation of measures to reduce ecological impacts.     

Interactions between flavonoids and proteins: effect on the total antioxidant capacity

Flavonoids are potent antioxidants. It is also known that flavonoids bind to proteins. The effect of the interaction between tea flavonoids and proteins on the antioxidant capacity was examined. Their separate and combined antioxidant capacities were measured with the Trolox equivalent antioxidant capacity (TEAC) assay. It was observed that the antioxidant capacity of several components of green and black tea with alpha-, beta-, and kappa-casein or albumin is not additive; that is, a part of the total antioxidant capacity is masked by the interaction. This masking depends on both the protein and the flavonoid used. Components in green and black tea, which show the highest masking in combination with beta-casein, are epigallocatechin gallate and gallic acid. The results demonstrate that the matrix influences the efficacy of an antioxidant.     

Ecology,classification and soil pattern of colluvial soils of the bornhoeved lake district (North-Germany)

Water erosion causes the accumulation of soil material, especially at the bottom slope and in landscape depressions. According to FAO-UNESCO (1990) colluvial soils can be classified as Cumuli-Aric Anthrosols if the minimum thickness of the altered topsoil is 5 dm or more. These soils are characterized by addition of small amounts of soil material that has been incorporated into the underlying material by tillage and/or turbation. As a result of geological factors and land-use intensities, Cumuli-Aric Anthrosols differ markedly in their ecological properties. In the study area ‘Bornhoeved Lake District (Schleswig-Holstein, North-Germany)’ soil patterns have been investigated showing the interdependence of soil landscapes and their soil units by water erosion and accumulation. Examples of various colluvial soils in catenary sequences in the study area are presented. Colluvial soils in the study area are characterized by a layer thickness between 5 and 14 dm and show significantly higher quantities of organic matter, nitrogen and plant-available water in comparison with eroded soils.     

Investigation on Soil Lipid Extraction with Different Organic Solvents

Soil lipid content is an important characteristic of the soil organic matter. One of the commonly used extractants for the determination of soil lipid is benzene/ethanol 1:1(v/v). In this study the toxic solvent mixture benzene/ethanol was substituted with the less harmful one toluene/ethanol 1:2.3 (v/v). Both solvent mixtures give a comparably high recovery of soil lipid and the composition of both lipid fractions are very similar according to their thin layer chromatography (TLC). Further investigations with NMR-spectroscopy confirmed that the extracted lipid fraction consists mainly (7gt;90%) of structure elements of aliphatic hydrocarbons.     

Extending Finlay–Wilkinson regression with environmental covariates

Finlay–Wilkinson regression is a popular method for analysing genotype–environment interaction in series of plant breeding and variety trials. It involves a regression on the environmental mean, indexing the productivity of an environment, which is driven by a wide array of environmental factors. Increasingly, it is becoming feasible to characterize environments explicitly using observable environmental covariates. Hence, there is mounting interest to replace the environmental index with an explicit regression on such observable environmental covariates. This paper reviews the development of such methods. The focus is on parsimonious models that allow replacing the environmental index by regression on synthetic environmental covariates formed as linear combinations of a larger number of observable environmental covariates. Two new methods are proposed for obtaining such synthetic covariates, which may be integrated into genotype-specific regression models, that is, criss-cross regression and a factor-analytic approach. The main advantage of such explicit modelling is that predictions can be made also for new environments where trials have not been conducted. A published dataset is employed to illustrate the proposed methods.