فهرست مطالب khalil zenalinezhad dr

Water deficient stress is one of the major limiting factors of wheat production in arid and semiarid areas of the world such as Iran. Under water deficient stress photosynthesis is limited and remobilization of assimilates stored in stems is more important to grain filling. In order to molecular analysis of fructan remobilization in wheat stem (penultimate) under terminal water deficit stress, T-65-7-1 mutant line (M7, the results of gamma irradiation) along with its wild type (cv. Tabasi), in terms of relative gene expression involved in biosynthesis and hydrolysis of fructan and transport of sucrose were studied. Water deficit treatment (30-40% field capacity) initiated at full heading stage (Zadoks 60) and sampling was conducted at two stages (7 and 21 days post anthesis). In the T-65-7-1 mutant line, a significant increase was observed in expression levels of genes involved in fructan biosynthesis (1-SST and 6-SFT), fructan biosynthesis (6-FEH) as well as sucrose transport (SUT1 and SUT2) compared to the wild type (cv. Tabasi). This event is due to more remobilization in T-65-7-1 mutant compared to the wild type. In T-65-7-1 mutant, during early grain filling period, 1-SST and 6-SFT produces more storage of fructan in the stem. Also, during rapid grain filling stage, 6-FEH produces more sucrose and finally, SUT1 and SUT2 transports more sucrose from stem to grain. In wheat breeding programs, 1-SST, 6-SFT, 6-FEH, SUT1 and SUT2 can be used as indicators for selecting genotypes with high fructan content and more remobilization.

Mutant genetic materials are valuable tools for understanding the physiology of remobilization and could be useful in the breeding of drought tolerant varieties. Two advanced mutant lines of bread wheat (T-67-60 and T-65-7-1) along with their wild type (Tabasi Cv.) were planted at two moisture conditions (normal and 30-40% of field capacity) as a factorial experiment in format of completely randomized design with three replications. Drought treatment initiated at full heading stage (Zadoks 60) and soluble carbohydrates were measured 5 times (0, 7, 14, 21 and 28 days after anthesis) in the stem internodes, separately. Based on the results it could be said that changes in the receiving signals for senescence phenomena under drought stress, capability of the sink, the rate of the reserves assimilated before anthesis and the use of reserves capacity over stem are the factors affecting the differences of genotypes in remobilization of stem soluble carbohydrates under drought stress. It seems that under drought stress mutant line T-65-7-1 was significantly better than wild type cultivar in terms of remobilization and its efficiency and also for faster receiving signals of senescence (as a stimulating factor of remobilization), higher capability of the sink (more grain yield) and higher reserve capacity (higher maximum soluble carbohydrate concentration and specific content). Also, mutant line T-65-7-1 has utilized full ability of all parts of the stem for remobilizing soluble carbohydrates during grain filling.

Identification of the appropriate dose for mutagen material is the most important step in setting experiment and creating mutant genetic material. According to a definition the most appropriate dose of mutagen is a dose that causing a reduction of 50% survival or 30% growth, compared to control. The aim of this study was to evaluate the effect of different doses of gamma radiation (0 as a control, 100, 200, 300 and 400 Gary) on the early growth characteristics for determining the appropriate dose of gamma irradiation in wheat cultivar Sardari. Therefore, an experiment was conducted based on completely randomized design with three replications at the laboratory and greenhouse. Data analysis of seed germination experiment showed significant difference in all traits including rootlet length, stemlet length, fresh weight of rootlet, fresh weight of stemlet, dry weight of rootlet and dry weight of stemlet, the exception of germination rate. Analysis of data obtained from a greenhouse, also showed significant difference in plant height and survival percentage. Based on the best fitted regression model and probit analysis determined a dose causing reduction of 50% survival or 30% growth, compared to control. It was in the range between 200 to 300 Gary, for Sardari cultivar. It could help to create adequate genetic diversity by applying this range of gamma radiation, for using in the wheat mutation breeding programs.