Iranian Journal of Rangelands and Forests Plant Breeding and Genetic Research
Year:2001 | Volume:- | Issue:6|Papers Count:9

Karyotypic studies were carried out on eleven populations in seven species of annual medics. The length of chromosome arms was measured in at least five well prepared cells at metaphase stage of cell division. The difference between the populations and chromosomes were tested using factorial experiment, based on a completely randomized design. Revealing significant differences between the populations and their chromosome dimensions, the populations relationships were investigated using several multivariate methods of analysis of variance such as cluster analysis and principal components analysis.Two groups of genotypes having 14 and 16 chromosomes were observed. Cluster analysis based on the short arms length of the chromosomes in the 14 chromosome group assigned three populations of M. polymorpha to one cluster, implying the usefulness of this character and the analysis method in identifying the relationship among the species. In the 16 chromosomes group, M. truncatula and M. radiata showed the most genetic distance based on the total length of the chromosomes.In principal components analysis, the characteristic of total length of the chromosomes, long arm length and long arm to short arm ratio showed the most influence in the first component formation. The first component also contained more than 98% of the data variation. Long arm to short arm ratio and short arm length characteristics had the most influence on the second principal component formation.

Seed and seedlings of several populations of Lolium rigidum were treated by 0.2% colchicine solution for 4 hours. The treated seeds and seedlings were washed by distilled water and transplanted in Jiffy pots. Some seeds were sown and studied cytogeneticaly and morphologicaly during second year. Seed was collected from the individual plants after completing the growing period. A number of seeds from the individual plants were cytogenetically investigated for the number of chromosomes and karyotypic characteristics. Seed was collected from the definitely proved polyploid genotypes. A number of seeds from each of the mentioned plants were sown in a randomized complete block design along with several other diploid and polyploid populations of Lolium species for studding morphological characteristics. The treated plants showed various effects for morphological characters, in which, multi-branchless of inflorescences was the main one. Progenies of several plants were proved to be autotetraploid. Several forms of anioploidies were also observed. The tetraploids were morphologically different from their parental diploid population.

Differential expression of low - temperature - induced genes was investigated in Agropyron desertorum and A.elongatum. Total RNA was extracted from the plants grown under 20/15°C (day/night) and at 6/2°C (day/night) temperatures. The RNA was then fractionated through electrophoresis, and accumulation of mRNAs corresponding to stress - inducible nsLTP and dehybrin gene families was analyzed, using northern hybridization.The mRNA level of the test genes increased in plants under 6/2°C, indicating gene expression enhancement in responses to low temperature stress. Also, cold hardiness was examined through a frost test, by assessment of survival in both control (20/15°C) and low - temperature (6/2°C) -treated plants after freezing. Freezing tolerance was improved in plants grown at low-non-freezing temperatures. Also, the levels of freezing survival and gene expression were higher in A. desertorum than in A. elongatum. A positive correlation was also observed between the degree of freezing tolerance and the exprossion of the cold-inducible genes, and this could be a useful result in clarification of the role of the genes in plant freezing tolerance.

In order to investigate ploidy levels in a Thyme species (Thymus kotschyanus), three populations of the species growing in north and north-west of Iran were studied for cytogenetical aspects. Long arm length, short arm length and total length of the chromosomes, number of chromosomes and ploidy levels were studied at least in five mitotic cells of each population.A population (accession) from Sirachal station, (in central part of south slope of Alborz mountain chain) was tetraploid (2n=4x=60). The other two populations, collected from Tabriz and Mianeh were diploid (2n=2x=30). Regarding kariotypic symetric assessment parameters results such as TF%, DRL% and S%, tetraploid population was more symetric than the other diploid populations, particularly comparing to the Tabriz one. This implies that the Tabriz accession is in a more degree of evolution than the others. Based on the kariotypic symmetric parameters and range of the chromosomes total length, the two accessions of Tabriz and Mianeh are suitable for breeding purposes such as in traspecific hybridization and genetic variation induction.

In order to study the genetic variation among local and foreign accessions/ varieties of perennial ryegrass (Loliumperenne) in Gene Bank of Natural Resources, an experiment was conducted in Alborz Research Center, Karaj, Iran. Seedlings of 29 genotypes were transplanted in the field using a complete block design with three replications. Each row plot was consisted of five spaced plants. Forage dry matter yield, basal cover, ear emergence date, pollination date, stem number, stem height and persistency at four harvesting dates were recorded. Data was analyzed using analysis of variance, principal components and cluster analysis. Analysis of variance showed significant differences among accessions/ varieties for all of the characters in each cutting, indicating the existence of genetic variation in (Loliumperenne) germplasm available in the Gene Bank of Natural Resources. Using principal component analysis, the first three components determined 72% of the total variation. Ear emergence date, pollination date, stem number and stem height in cut1 and annual dry matter were the most important traits in first components. Basal cover, stem number and stem height of cut 2 and persistency were the important traits in second components. The 29 genotypes were grouped into 5 clusters based on multivariate analysis of 16 classification variables. Accessions in cluster 1 averaged well above the overall mean for productivity and persistency. Only one accession was in cluster 2 that was late maturity and had lower dry matter yield, tiller number and tiller height. The accessions in cluster 3 were tetraploid and late maturity. They had more dry matter yield in cuts 2 and 3. Cluster 5 characterized by early maturity, higher dry matter yield, higher stem number and higher stem height in cut1. But, it was less persistent than other clusters. Distribution of genotypes based on the first two component scores was in agreement with cluster analysis. Considerable heterosis would be obtained in crosses between populations from more widely genetically separate groups.

Anatomic characteristics of elite adult trees of P. caspica and in vitro derived plants were compared. Results showed that plants from natural environment (Genotype 1,2) are different from Genotype 3 , because of less cuticole and tricomes on epidermis cells in the former(s).All of the plants showed oxalate calcium crystals in both collenchymatic cells of leaves and parenchymatic cells of petioles. Adult plants showed vascular bundles with a scleranshima ring around the phloem, but tissue cultured explants showed less cuticoles and tricomes on epidermis, small and restricted vessels without scleranshima ring. Also stomata were anemositic and bulgy in all of the test samples method of search is the microtome sectioned from leaves and petioles stained them, fixationed and microscopic studied between adult trees and tissue cultured species.

Wild servis tree (Sorbus tormhnalis) is an important forest species for wood production in Iran. This experiment was conducted for shoot proliferation in this species. Apical and lateral buds from elite trees were collected in northern forest (Loveh, Farim and Pardcola) in different seasons (spring, autumn and winter). Sterilized explants were then cultured on basal MS medium.The results showed that the best treatments for explants sterilizing were:-1% (w/v) Benomyl for 30 minutes- 70% Ethanol for 5 seconds-0.1% Mercuric chloride with 1-2 drops of liquid soap for 1 minute. The results indicated that the best season for taking explants from mother plants was late autumn. The suitable media for explants establishment and shoot proliferation were basal MS supplemented with 0.5 ppm BAP and 1/2N basal medium with 1 ppm BAP, respectively. Using GA3 was not effective for stopping rosette growth and increasing internodes length.

The Onobrychis genus in the family of Papilionaceae contains about 60 species in Iran. These species are adapted to various climates of Iran. This study has been done to find their habitats and to collect the existing species as plant samples. To identify the species, Flora Iranica was used. Results showed that there are 16 habitats containing 7 species in Fars province which can be divided into 3 groups according to climatic conditions of the province. These are: Onobrychis cornuta, O. crista-galli, O. Gaubae, O. melanotricha, O.Aucheri, O.ptolemaica and O. sojakii.