Evaluation of different treatments in sexual reproduction of Populus caspica Bornm. for broadening its genetic basis in the nature

Populus caspica Bornm. is an endemic and fast growing tree distributed in northern Iran, considered as endangered species without proper sexual reproduction in natural conditions. In contrast to other poplar species, knowledge about regeneration of this species is little. The tree yearly disperse plentiful of short-lived tiny seeds that need the suitable conditions and substrates to germinate and grow. Usually, the required conditions are not available in its natural habitats. The study was carried out to consider the mentioned problem. Therefore, for mass production of seed-born seedlings and broadening genetic basis of the species, matured capsules were collected from 25 single trees, distributed at different sites in Golestan, Mazandaran, and Guilan provinces at early April 2010. Sixteen trees of the 25 trees produced suitable and enough seeds. After well sifting, 30 seeds of each tree were sown per pot at three different soil treatments including: i) only nursery soil, ii) combination of nursery soil and fine sand (wind shifting sands), and iii) only fine sand, as well as three light aspect treatments including: 1) Eastern aspect, 2) Southern aspect and 3) Western aspect for 16 provenances. The experiment design was factorial model based on Completely Randomized Block Design with three replications. Pots were kept in large basins and irrigation was done daily in basin and pots. Weed control was done at different dates during growing season. Height of all seedlings was recorded at the end of growing season. Results of analysis of variance showed significant differences among all of the sources of variance. Soil treatments caused 113, 57 and 0 centimeters in seedling height, respectively. Significant differences were observed among the mother trees based on their seedling height. The results indicated that the progenies of Zarringol 2, Zarringol 3, Kenesy and Golestan 4 trees revealed 111.4, 98.9, 98.9 and 94.3 centimeter in height, respectively as the longest one, so that 11 groups were specified among the 16 mother trees. Significant differences among the direction treatments were observed, so that the seedling height of 87.6, 87.3 and 81.4 centimeters were recorded for eastern, southern and western aspects, respectively. As a main result, the study shown significant differences for height in soil, mother trees and light aspect treatments. Therefore, mass seed-born seedling production for the species would be possible using the best treatments of the study.