Application of gamma irradiation on morphological, biochemical, and molecular aspects of wheat (Triticum aestivum L.) under different seed moisture contents.

Nuclear technology is currently used as a tool in mutation breeding to improve crops by increasing genetic variation. The ionization of gamma rays produces large amounts of free radicals, simulating stressors in the natural environment. To avoid gamma-ray-induced oxidative stress, plants use antioxidant defense systems. Exposure of plants to irradiation can affect the germination, growth, and production of metabolites. Plants' sensitivity to irradiation depends on genetic and environmental factors such as moisture content. For this purpose, the effects of different gamma irradiation doses [0, 100, 200, 300, and 400 Gray (Gy)] and different seed moisture contents (7, 13, and 19%) on traits such as seed germination, seedling growth, molecular and biochemical alterations in antioxidant enzymes were examined in the current study. Based on the results, the highest seed germination percentage was observed in the interaction effect of seed moisture at 13% with an irradiation dose of 400 Gy (98.89%). Seedling survival percent and seedling length decreased with increasing doses of gamma irradiation at different seed moisture contents. Increasing gamma irradiation doses were reduced root and stem fresh and dry weight, and root and stem length. The highest level of catalase enzyme activity and expression was observed at 200 and 300 Gy irradiation doses at different moisture contents. The peroxidase and polyphenol oxidase gene expression were reduced at all contents of gamma irradiation doses and seed moisture compared to the control. It can be concluded that the dose of 200-300 Gy of gamma irradiation reduced plant growth by 30% in terms of fresh and dry weight and length of plants, as well as enhanced the expression of antioxidant enzymes. The results of this study could help plant breeders select an appropriate dose rate in wheat for further research.

Alteration of physiological and biochemical properties in leaves and fruits of pomegranate in response to gamma irradiation.

Pomegranate breeding to improve the marketability requires the production of large and high quality fruits. Gamma radiation on pomegranate can be used to generate genetic diversity that allows the breeder to screen the mutants for superior quality and quantity. For this purpose, dormant buds on 1-year-old shoots of pomegranate cultivar "Malase Saveh" were subjected to 36 Gy (Gy) of gamma irradiation from a cobalt (60CO) source. Shoot cuttings were taken from the mutated shoots and generate M1V2. The number of 11 mutants were selected from M1V2 plants based on their winter survival and disease resistance. After a period of 3-4 years, leaf and fruit samples were harvested from the M1V5. Results showed that physiological and biochemical parameters of leaves were altered unevenly, some clones showed no alterations from the control, while others revealed considerable differences. Irradiation altered various aspects related to fruit, such as the number and weight of ripe and unripe fruits, number of cracked, sunburn, worm-eaten fruits, and fruit size. In general, mutant clones 5, 8, and 10 had higher fruit sizes and weight of ripe fruits and less number and weight of unripe fruits. The stability of the detected mutants will be evaluated and new commercial field trials using selected materials will be established.

Reducing nitrous oxide emissions from irrigated maize by using urea fertilizer in combination with nitrapyrin under different tillage methods.

The aim of this study was to evaluate the effectiveness of nitrification inhibitor (nitrapyrin; NI) as a mitigation option for yield-scaled emissions of nitrous oxide (N2O) under tillage management and urea fertilization in the irrigated maize fields in northern Iran. A split-plot experiment was performed based on a randomized completed blocks design with three replicates. The main plots were the levels of tillage practices (conventional tillage (CT) and minimum tillage (MT), and the subplots were the fertilizer treatments (control, urea, and urea + NI). The gas samples for measuring N2O emissions were collected during the maize growing season from June to September, using opaque manual circular static chambers. Soil samples were taken at 0-10 cm to determine water-filled pore space, ammonium (NH4+), and nitrate (NO3-) concentrations in the soil. When the crop reached physiological maturity, maize was harvested to measure grain yield, biomass production, N uptake of aboveground, and nitrogen use efficiency (NUE). The results showed that the applying NI in combination with urea reduced the total N2O emissions by up to 58% and 64% in MT and CT, respectively. In the urea + NI treatment, mean soil concentrations of NH4+ and NO3- were significantly higher (20%) and lower (23.5%), respectively, compared with other treatments. The NI reduced the yield-scaled N2O-N emission up to 79% and 55% for CT and MT, respectively. Furthermore, compared to treatment with urea alone, the application of NI increased the NUE of the MT and CT systems by an average of 55% and 46%, respectively. This study emphasized that the application of nitrapyrin should be encouraged in irrigated maize fields, in order to minimize N2O emissions and improve NUE and biomass production.

Application of gamma rays on salinity tolerance of wheat (Triticum aestivum L.) and expression of genes related to biosynthesis of proline, glycine betaine and antioxidant enzymes.

We investigated the effects of salinity stress and gamma radiation on salinity tolerance in wheat crops. To this end, mutant lines were generated by exposing Arg and Bam wheat varieties at the primordial state to 150 and 200 gamma radiation doses in the field. The top 15 mutant lines were specified for cultivation in the fifth-generation under two conditions, including non-stress and salinity stress. According to Fernandez's model, the three mutant lines had high yields under both conditions. The three mutant lines were selected with their two parents, and then, cultivated in a completely randomized factorial design in a greenhouse under non-stress and salinity conditions. The mutant lines showed significantly higher osmotic adjustment, leaf relative water content (RWC), potassium ion concentration, soluble sugar content and lower proline (Pro), and glycine betaine (GB) content than the parents at both the vegetative (VEG) and reproductive (REP) stages under salinity conditions. The expression of genes involved in the Pro biosynthesis pathway, P5CS and P5CR genes, in mutant lines were less than their parents, and conversely, P5CDH in mutant lines was more than their parents. The changes in the expression of CMO and BADH genes involved in the GB synthesis pathway indicated that the mutant lines had less gene expression compared to their parent genotypes of Arg and Bam. The results indicated an increase in antioxidant activity in the mutant lines compared to their parents. Consequently, irradiated plants have probably adapted to the salinity stress by increasing the osmotic adjustment, RWC, potassium ion concentration, and soluble sugar content, as well as activating antioxidant enzymes.