In this investigation 15 superior poplar clones with wide crown were selected from the first stage of the Selection Nurseries Trial. One year old seedlings of the clones were planted under the statistical design of Randomized Complete Blocks at Karaj Natural Resources Centre in 1999 (75 seedlings at each plot). At the end of each growing season diameter at breast height (dbh) and height were measured. After calculating mean height and diameter of the clones, their mean, current and total growth volumes were determined. The mean growth volume data was analyzed using the MSTATC computer software. The results of 10 year old trial shows that among the investigated poplar clones, Populus euramericana vernirubensis with diameter of 24.6 cm and Populus euramericana 154 with height of 18.57 m achieved the greatest diameter and height growth rate, respectively. There was significant difference between P. euramericana vernirubensis and P. alba nivea in average volume growth rate (27.45 and 9.02 m3/ha/y, respectively). During the 10 year growth period, the highest current volume growth of the poplar clones belonged to years 1996-1998, because 52.18 to 64.2 percent of the total growth developed during these three years. P. deltoids Particularly P. deltoides 73/51 was the most tolerant species whereas P. alba (P. alba nivea) and P. nigra (P. nigra 42/51) were the low tolerant species to pest infection.

World increasing demand for wood production, caused the increasing impact to natural forest. Short term exploitation and improvement of wood production have been reduced these impacts. Considering the special characteristics of poplars, plantation of these fast growing species could be a proper solution to solve the problems. This research was carried out with the aims of increasing wood production by collection of better and more adaptable poplar clones to climatic and edaphic condition in Markazi province. In this research, 21 poplar clones were compared using the complete experimental block design in 3 replications. ِDiameter at breast height and height of trees were recorded and total volume and volume increment were calculated. Based on results, we concluded the following results: higher diameter, height and volume increment were found in Populus nigra 56.72 with 20.7 cm, 17.57m and 36.55 m3/ha/years, respectively. Other promising clones are P.nigra 72.19, P.nigra 72.5 and P.nigra betulifolia. The poorest results were observed on different clones of populus alba.

In this trial 10 poplar clones (Populus deltoids with 8 clones, P. euramericana 561/41 and P.alba as control) were studied on marsher land of Geshlagh river at Sanandaj during 2001-2005. Planting of cuttings were accomplished in early March of 2000 and transplanting of saplings were conducted in late March of 2000 in spacement of 4x4 m based on randomized complete block design (RCBD) with 3 replications. Each plot contained 25 saplings that were planted as 5x5 (9 saplings as main and 16 as buffer). Some of morphological, phenological and qualitative characteristics were measured every year. Results showed that diameter at breast height (dbh), height (h) and cumulative volume (cv) at end of trial was 14.7cm, 9/88 m and 0.0931 m3, respectively. Analysis of variance showed significant differences at p £0.01 among Poplar clones for all studied factors. This provides a very suitable background for selection of superior varieties. Duncan test for Poplar clones showed that clones of P.d. 63/2. P.e. 561/41and P.d. 63/1 with diameter of 18.1, 16.99 and 16.6cm, height of 12.11, 10.77 and 10.95 m, cv 0.1612, 0.1214 and 0.1220 m3 per tree, average of annual volume increment with 0.04029, 0.03101 and 0.03050 m3/y for each tree and mean annual volume increment per hectare of 25.18, 19.38 and 19.06 m3/y/ha, respectively, were superior clones among studied clones until this stage. Superior clones had crown diameter (CD) about 3.68 -3.9 m, good vitality, mainly safe from a contamination by pests and clear trunks. The wood production of superior clones was 1.5-2 times more than total average and 5-7 more than the standard clone (P.alba saghez).

Plant viruses are important because of their threat to produce of crops products and also their application as research tools in molecular plant pathology and other fields in biotechnology is important. The most research and achivments in plant pathology depends on ability of plantchr('39')s viral genomes to preserve, replicate and modify as infectious clones. The infectious clone is a full-length DNA clone in which infectious transcripts can be obtained in vitro or in vivo conditions with a suitable promoter. Infectious clones can be used to study the life cycle of viruses, replicate and express of viral genomes, understanding of virus-host interaction, functional genomics and germplasm screening as a part of pre-replication programs for virus resistance. However, the infectious clone of plant viruses may pose a risk to the environment due to its ability to return to the wild-type mode through recombination. This scientific review introduces the infectious clone in plant viruses and surveys the advantages and disadvantages of working with genetically modified plant viruses.

Required number of female flowering branches from two species of Papulus nigra and P. delta ides were placed in water and soil in a greenhouse on late February and early March 2000. Female flowering branches were also grafted on one year old seedling stocks of the species, before catkins elongation and exposition, planted in the plastic pots. Pollen was collected in suitable times from appropriate male plant branches, being kept in different cool temperature. Pollination was done by a fine brush on the female flowers several times per day for two to three consecutive days to make sure all parts of the catkin flowers receive enough pollen. Mature hybrid seeds were directly sowed well moisture soil. Embryo rescue technique was also used to develop the immature hybrid seeds and embryos. Free growth regulator half MS, MS and B5 agar medium were used to perform the technique. Six leaved seedlings were transplanted in well incubated soil.

Identification of Poplar clones is necessary, Particularly at early stage of growth, to demonstrate their similarity and diversity in selection process. Identification and selection of poplar clones was carried out using morphological attributes after a process period of 10-15years. Although this approach, renders some information about the clones growth characteristics, but requires relatively high costs for time and site. In this study 12 clones belonged to four species were planted under randomized complete blocks statistical design with three replicates and their data were recorded during the years 1999-2001. Twenty distinctive morphological attributes of the poplar clones leaves, branches and roots which according to the new methods can be applied to identify clones and species at early growth stages, were measured at different times. The data were analyzed using various univariate and multivariate statistical methods including analysis of variance, cluster analysis and principal component analysis. The results shows that the morphological markers in conjunction with appropriate statistical methods are able to differentiate poplar clones. There were significant differences between the species and clones, regarding their morphological characteristics. Although univariate analysis was not suitable for systematical classification, but multivariate analyses such as cluster and component analyses were the best for the clones and species classification. Overall, the clones of the species P. alba, P. nigra, P. euphratica and P.deltoides were classified at separate groups.