Iranian Journal of Rangelands and Forests Plant Breeding and Genetic Research
Year:2001 | Volume:- | Issue:4|Papers Count:7

To study the effective factors on seed germination of Haloxylon, the effects of four different temperatures on several randomly selected Haloxylon aphyllum and H persicum trees, seeds were investigated. Then seeds were collected from three different positions, top, middle and down part of the trees crown of eight Haloxylon aphyllum and two H persicum which were randomly selected from Yazd province Haloxylon habitats.These were studied for seed germination percentage in five consecutive times with ten hours intervals.The first experiment revealed that not only the genotypes are significantly different for seed germination percentage and the temperatures have different effects on the seed germination of the studied genotypes and species but also there are significant interactions between the two factors, genotype and temperatures.As well as different capacity of seed germination between the trees, the second experiment showed that the seeds from different positions of the trees are significantly different in germination capacity. The seed collected from the top part of the trees germinated better than the seeds collected from lower parts of the trees. This experiment also revealed that the germination speed, between the two species are different and H.persicum germinates faster than H.aphyllum.Fast germination in Haloxylon aphyllum is considered as a way of adaptation to saltyJl1lddrought areas, so that, if enough moisture is prepared for the seeds in a short period, the seeds can germinate and establish very fast.

Understanding the environmental conditions in vessels of tissue cultured plantlets could help us to prepare optimum conditions, and hence improve the production efficiency in micropropagation. Plantlets of wild cherry were studied in culture vessels, using two different types of caps, conventional non-vented cap (NYC) and filtered vented cap (YC). CO2 concentrations in vessels, in general, were lower, compared with atmospheric CO2, but more reduction in concentration was observed in NYC. When the light intensity was increased, more depletion of CO2 in the vessels was measured. However, no significant differences in photosynthetic performance (Pm) were observed in plantlets under two treatments. Transpiration rate and stomatal conductance of plantlets in VC were lower and this could be due to improvement in stomatal functioning. This improvement, in turn, has been attributed to lower relative humidity (RH). In this experiment RH in YC vessels was 17% lower than NYC.

Salintiy is an important environmental stress which restrict agricultural yield. The effect of salt (NaCl) was studied on germination and vegetative growth of two alfalfa (Australian line 2129 and Ghra-Youngeh, Iranian alfalfa) and one sainfoin from Golpaygan, Iran. The split-plots experimental design was used to carry out the main effect (genotypes) and salt levels as sub plots (0, 75, 125, 175 and 225 mM). There were two separate experiments, one for germination and the other at vegetative stage. Plants were establish in the pots at glass house. All pots were irrigated for 52 days with tap water. Then, they irrigated with 200 cm3 water containing the five levels of salt, for 49 days, and one time per week.The leaf water potential, shoot height, root length and shoot and root dry weight were recorded. At low levels of salinity (0, 75 and 125 mM), the Australian line 2129 had greater germination and vegetative growth than the Iranian alfalfa (Gharah-Youngeh) and sainfoin, whereas at high levels of salinity (175 and 225 mM) Gharah- Youngeh had greater germination and vegetative growth than the Australian alfalfa and sainfoin.Although the Golpayganian sainfoin had lower growth rate than the two alfalfa genotypes at all levels of salinity, but had lower leaf water potential. It means, sainfoin may have greater salt tolerance.

Since a high level of polyploidy may play an important role in increasing forage dry matter yield, a number of natural populations of Lolium species were investigated for their ploidy level and other kariotype characteristics. In each population of Lolium perenne and L. rigidwn, chromosome characteristics were studied and measured at metaphase stage in five cells. The short and long arms of the chromosomes were measured and analysed. Three polyploid populations were detected within the studied populations. Two populations of L. perenne and one population of L. ligidum were tetraploid with 28 chromosomes. Means of short and long arms of chromosomes, their relative standard errors and the populations karyotypic formula were determined. The three populations were in the same situations based on TF%. Regarding DRL values, since smaler value of this parameter indicates more chromosome asymmetry, one of the L. prenne populations was more symmetric than the other two populations. Based on this parameter L. ligidum population had the most asymmetric karyotype.

Twenty three alfalfa cultivars were assessed in term of forage production in 8 diverse climatic conditions of Iran. The experiments were conducted for 3 to 6 years and the experimental design was RCBD or split-plot. In the first year, due to weak vigor of the plants and good establishment no harvest was made, but from the second year each year one cutting and in some cases, two cuttings were done. Furthermore, the plant height and leaf percentage were measured and comparer for each cultivar and climatic conditions. Forage yield of the alfalfa cultivars in different climatic conditions was different. In North of Khorassan province, with annual rainfall of 279 mm and climatic condition of cold dry and cold semi-dry, all cultivars produced more than 3 tones of herbage. Alfalfa cv. Simercheskaya, Krisari and Kharvandeh were superior to the other cultivars in term of herbage production. In Agh-Gola (Golestan province) with annual rainfall of 315 mm and climatic conditions of semi-arid, forage yield of the plant ranged between 2.8 and 3.8 tons/ha. The cv. Kankrip produced the highest yield.In climatic condition of cold stepic and cold semi-steppic (Chadegan, Zagheh, ghaed rahmat, Taleghan herbage yield varied from 1 to 2.2 tons/ha). In these regions, cv. Cody, Simercheskaya and krisari produced the highest yield. In Caspian climatic condition with annual rainfall of 400mm cv. Hunteriver, Krisari and Cody were superior than the other cultivars. In climatic condition of cold semi-arid of Zanjan, all the cultivars produced the lowest herbage yield and the experiment should be done again. Leaf percentage like forage production was different among climatic conditions and alfalfa cultivars. The plants in Chadgan produced more leaf than the plants in North of Khorassan and caspain climatic conditions. The plants which harvested in cold climatic conditions like Taleghan, 43 to 48 percent of the herbage belonged to their leaves.The plant height was between 45 to 70 cm in diverse climatic conditions and the heighest herbage production and plant height were obtained in North of Khorassan and Lorestan.