Seven ectomycorrhizae on oak (Quercus robur L.) from a Slovenian forest stand are described, five of them for the first time in detail. Four of these species could be identified (Lactarius chrysorrheus (Fr.) Fr., L. serifluus DC. ex Fr., Xerocomus subtomentosus (L. ex Fr.) Quel., X. armeniacus (Quel.) Quel., one unidentified species was given a preliminary name ("Quercirhiza squamosa"). Two identified species, already comprehensively characterized on other tree species, are presented shortly (Laccaria amethystina (Bolt ex Hooper) Murr., Cenococcum geophilum Fr.). Whereas some of the encountered species show considerable host specifity with oak (Lactarius chrysorrheus, L. serifluus and, in a lesser degree Xerocomus armeniacus), other species have a broader host range and can even grow with conifers (Xerocomus subtomentosus, Laccaria amethystina, Cenococcum geophilum). A key for all species was established. A possible use of ectomycorrhizal species as bioindicators is discussed.

Because of thinning of the ozone layer, there is a continual increase of ultraviolet B (UV-B) irradiation reaching the Earth. We have followed for two and a half years the influence of an artificial source of UV-B irradiation of 17685 J/m** 2 and 28010 J/m** 2 on spruce Picea abies (L.) Karst seedlings. The controls were irradiated with only normal, 6025 J/m** 2. Results show that 3 years seedlings are sensitive to irradiation, as may be first seen from their decreased mitotic activity and in lesser needle and seedling growth in their third year.

A plant test system by the classification of chromosome aberration in the root tip meristems of young spruce plants (Picea abies (L.) Karst.) has been used to study the environmental influence on the genetic material of trees at natural sites and under defined conditions of greenhouses and open-top chambers. All our results suggest that this plant test system is a valuable tool in environmental monitoring.

Needles of 20 years old spruces from Prednji vrh, in the area affected by the Sostanj power station, and from Pokljuka (Alps region, with a relatively unpolluted environment), were analysed for total sulphur content (St). Measurements were taken in a period between April and August twice monthly and in the period from August to April every four weeks (May 1993 - June 1994). Sulphur content in one and two years old spruce needles from Prednji vrh were much higher (one year old needles 2.06-2.50 mg/g needle dry weight, 1993) than in needle samples from Pokljuka (one year old needles 1.05-1.25 mg/g needle dry weight, 1993).

Endophytic fungi species composition in healthy needles of Austrian pine (Pinus nigra Arn.) was investigated at eight locations in Slovenia. Results from October 1994 and January 1995 isolations were compared with analyses of macronutrients, sulphur and lead content of the needles. About 80 species of microfungi were revealed. From the observations and measurements described it was not possible to discriminate between the effect of environmental factors and effect of air pollutants. The pollutants load of all measured elements is low and the environmental factors are very diverse. From the dendogram of isolation frequencies it seems that the age of the tree affects the species composition and frequencies of endophytes to the greatest extent.

Three principal approaches are used in our laboratory to analyze plant genomes: (i) The construction of high density molecular maps: We have established a refined microdissection procedure to construct chromosomal and subchromosomal libraries. Synchronized meristematic root tip tissue from which metaphase spreads can be prepared with a novel dropspread technique in combination with nl-scale PCR allowed the cloning of DNA of 10 or less chromosomes or chromosome segments. The construction of high-resolution maps from discrete genome regions can greatly facilitate genetic fingerprinting, gene isolation and QTL studies. (ii) Synteny analysis: The Aegilops-based deletion mapping system in wheat with an array of deleted chromosome parts and chromosome-specific RFLP markers has lead to the construction of a high density physical consensus map of wheat. The integration of wheat, barley and oat RFLP markers proves the colinearity between the wheat A-, B- and D-genomes, the H- genome of barley and the E-genome of Agropyron. (iii) Gene mapping in situ and chromosomes at high resolution: For the sensitivity enhancement of fluorescence in situ hybridization (FISH), the efficient preparation of plant chromosomes for high resolution scanning electron microscopy, mapping of low-copy sequences, and for comparative in situ hybridization a modified drop technique for plant protoplasts was developed. A tandemly amplified repetitive sequence element from microdissected barley chromosomes has enabled the karyotyping of single Gramineae genomes in a single step. These sequences are also useful for simultaneous double or triple hybridization experiments in an attempt to localize new sequence on specific chromosomes or chromosome segments. The physical mapping of the Sec-1 locus has been refined on the satellite of chromosome 1R of rye, and the syntenic locus on barley chromosome 1H identified. A method was developed for in situ hybrization and signal detection at high resolution using a field emission scanning electron microscope and a backscattered electron detector. Colloidal gold particles were localized on chromosome structures resembling the 30 mm fibre. Comparatively, an rDNA probe was located in the secondary constriction and highly compact adjacent regions of barley chromosomes.

Annual research has proven that the level of the so called natural cytogenetic damage to Norway spruce in Slovenia has been correctly estimated at 8. The results of cytogenetic bioindication calculated in accordance with this level show that average cytogenetic damage in the period from 1985 to 1992 enable us to determine environmental influences on the expression of cytogenetic damage.

Preliminary results and methodology related to the use of the fluorescence in situ hybridization technique for detection of plants hybrids are presented. Total genomic DNA probe preparation and the non-isotopic biotin probe labelling technique is presented. The use of an excess of unlabelled competitor DNA from a related plant species gives more constant results in determining whole plant genomes with in situ experiments on plant hybrids. Preliminary results of flourescence in situ hybridization for detecting alien rye chromatin and localisation on metaphase chromosomes and interphase nuclei in the bread wheat cultivar Yugoslavia are described. The methodology for detection of interspecies hybrids of common and sessile oak with flourescence in situ hybridization is given. The advantege of the use of total genomic biotin labelled probes for in situ hybridization is that it requires less effort than preparing species specific probes and the ease of interpretation of the results. The technique of fluorescence in situ hybridization is less species than other cytological techniques for higher plants and almost the same methodology can be used for detection of oak hybrids. The extraction of a high quantity of species specific DNA of high quality and probe preparation and labelling are the most important step.

Forest soil was sampled on two different observation plots by following well described methodology. Sampling sites had been chosen in place with typical soil conditions for the observed forest site. To make sampling easier some natural forest site characteristics were considered. Mg, Zn and Cd were determined by atomic absorption spectroscopy in all samples. Results were statistically evaluated and different sources of variance were estimated. It was also estimated whether the number of samples was sufficient for our requirement for accuracy of analytical results.