Iranian Journal of Seed Research

Effect of Zinc and Boron Application on Wheat Mother Plant under Heat Stress on Cell Membrane Integrity of the Produced Seed and Physiological Quality of Seedling

Hamid Reza Eisvand

Extended Abstract
Introduction: Providing important and effective elements such as zinc and boron- especially in areas where the soil for some reason cannot meet the needs of the plant- will be a good solution to improve seed and seedling quality and nutrition, and community health status. A considerable part of the wheat producing regions in the country are faced with late season haet during seed development stages. Thus, the present study will investigate the effect of heat stress and mother plant nutrition with zinc and boron micronutrients on seed deterioration and physiological quality of wheat seedlings.
Material and Methods: In a field experiment, wheat seeds were planted on two suitable planting dates (November 20) and late (January 5) to apply late-season heat stress during the seed development stage with three replications in Ramhormoz, Iran. The nutrition of mother plants with zinc and boron elements was done at three levels (nutrient-free and application of zinc and boron) as a foliar application. After harvest, the seeds were transferred to the laboratory and membrane integrity of seed cells was investigated using an electrical conductivity test as an indicator of deterioration. Another part of the seeds was planted in a factorial pot experiment based on RCBD with three replications to evaluate the quality of seeds and seedlings in the greenhouse.
Results: The results showed that exposure of seeds to heat stress during development reduced seed quality as well as seedlings so that the cell membrane in the seeds produced under heat stress conditions was damaged and their electrical conductivity increased by 19%. Also, these seeds showed more sensitivity to deterioration. The percentage of seedling emergence in the stressed seeds decreased by 21.66%. Heat stress also reduced seedling quality indices such as chlorophyll content, shoot dry weight, and root dry weight. Application of zinc and boron on the mother plant not only led to improved quality of seeds and seedlings under normal conditions but also the negative effects of heat stress on seed and seedling quality were reduced. There was a significant negative correlation between the seed electrical conductivity test and qualitative parameters. Therefore, the use of this test is recommended to determine the quality of seeds, especially seeds produced under late-season heat stress conditions.
Conclusion: Noting the negative effect of heat during seed development on seed quality, planting dates should be adjusted as much as possible so that the seed development stage does not coincide with the late-season heat stress. Due to the beneficial effects of using zinc and boron in the mother plant on many traits related to the quality of seeds and seedlings, their application- especially zinc- in soils with deficiency or the possibility of heat stress at the end of the season is recommended.

Highlights:

Zinc and boron micronutrients were used to mitigate the harmful effects of heat stress on seed quality.
Physiological characteristics of seedlings obtained from seeds produced in the field under late-season heat stress conditions were investigated.

Investigating the Effects of Natural and Artificial Seed Deterioration on Reactive Oxygen Species, Antioxidant Enzymes, and Seed Germination Characteristics in Local and Improved Rice (Oryza sativa) Cultivars Derived from the Farms in Guilan Province

Seyed Mohmmad Reza Ehtehsami

Extended abstract
Introduction: Seed deterioration is associated with oxidative stress and uncontrolled accumulation of reactive oxygen species. Seeds have a group of enzymatic and non-enzymatic antioxidants that protect them against reactive oxygen species and help maintain seed vigor and support seed germination processes. The response of different cultivars to seed deterioration is different. Knowledge about the sources and mechanisms of deterioration and how different cultivars respond can help to select the appropriate cultivar for the region and also provide useful information in selecting and applying appropriate management methods for storage and increasing the storage time of seeds.
Materials and Methods: The Experiment was conducted as factorial based on a completely randomized block design with three replications. Treatments included one and six months of natural storage (4˚C, 11 percent moisture content of seeds and 60% RH) and accelerated aging (96 hours at 45˚C and 100% RH) applied on four cultivars including Hashemi, Gilaneh, Khazar and Domsiyah. Germination percentage, germination rate, shoot length, radicle length, shoot dry weight, radicle dry weight, shoot vigor index (SVI), α-amylase activity, catalase (CAT), peroxidase (POX), superoxide dismutase (SOD) activity, malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) content were evaluated.
Results: The results showed that accelerated ageing and storage of seeds for six months led to reduced germination percentage, germination rate, shoot length, radicle length, shoot dry weight, radicle dry weight, shoot vigor index (SVI), α-amylase activity reduced in all four cultivars. This decrease was accompanied by an increase in the free radical content of MDA and H₂O₂ and a decrease in the activity of the antioxidant enzymes SOD and POX. Malondialdehyde content was lower in the seeds stored for six months. The activity of CAT increased after deterioration treatment, this increase was more intense in the seeds stored for six months. These seeds also showed lower H₂O₂ content compared to accelerated aging seeds. Khazar cultivar showed lower H₂O₂ content as a result of higher CAT enzyme activity. Moreover, this cultivar showed better germination percentage and germination rate after deterioration treatment compared to other cultivars. The decrease in germination percentage due to deterioration in Domsiyah was very severe. This cultivar showed the lowest germination percentage, germination rate, seed vigor and α-amylase activity in the accelerated aging treatment. Gilaneh and Hashemi cultivars showed higher germinability, α-amylase activity and SOD and POX at the beginning of the experiment, but after deterioration treatment, their germinability decreased along with the activity of antioxidant enzymes.
Conclusions: In all studied cultivars, the accelerated aging and storage of seeds for six months adversely affected germination rate. This decrease was accompanied by an increase in free radicals in the seeds and a decrease in the activity of antioxidant enzymes SOD and POX, which were less severe in Khazar cultivar and more severe in Domsiyah cultivar. These results indicate the greater importance of the storage conditions in Domsiyah cultivar.

Highlights:
1- The effect of storage and seed deterioration on the activity of antioxidant enzymes, reactive oxygen species and seed germination in rice was investigated.
2- The results of accelerated aging test and natural aging were compared for a better conclusion about the response of the cultivars.
3- The two improved cultivars were compared with two local cultivars (with high cultivation area).

The Effect of Chilling and Gibberellic Acid on the elimination of Schrophularia striata Seed Dormancy in Different Habitats of Ilam Province

Amin Salehi

Extended Abstract
Introduction: Schrophularia striata is one of the medicinal plants of the Scrophulariaceae family and contains phenolic compounds. Locals have traditionally used this herbal medicine to treat infections caused by wounds, gastrointestinal diseases, and eye diseases. Due to excessive consumption by indigenous people and climate change, especially increasing temperature, the cold required to eliminate seed dormancy is not presently available and its germination and growth has decreased. Therefore, this plant is at the risk of extinction. Since this plant is propagated in natural habitats through seed and due to deep seed dormancy, evaluation of different seed dormancy methods is necessary for conservation and domestication of this species. In this study, suitable methods to eliminate seed dormancy of this plant using chilling and gibberellic acid treatments were studied on the seeds collected from different habitats of Ilam province.
Materials and Methods: To investigate the effect of using chilling and gibberellic acid on Schrophularia striata dormancy, a split plot factorial experiment based on completely randomized design with four replications was conducted at the seed laboratory of Yasouj University in 2018. The first factor included the duration of moist chilling period (0, 4, 8, 12 and 16 weeks), the second factor included gibberellic acid (0, 300 and 600 mg/L) and the third factor included five habitats (Ilam, Ivan, Mehran, Abadan and Dehloran).
Results: The results showed that the 16-week Chilling and zero gibberellic acid treatments had the highest germination percentage in all habitats, as the percentage of germination in Mehran, Ivan, Ilam, Abadan and Dehloran habitats was 66, 50, 36, 30 and 25%, respectively. Also, the highest germination rate was observed in all habitats at 16 weeks chilling and zero mg/L gibberellic acid concentration. The highest germination uniformity was obtained at 16 and 12 weeks of chilling.
Conclusions: Chilling period duration was effective on germination percentage and rate and with increasing chilling period, germination percentage and rate increased. This indicates that the seeds studied had some degree of physiological dormancy, and the seed of higher altitude habitats required longer chilling periods than those of the lower ones for germination. Also, according to the results of this experiment, chilling periods above 16 weeks should be used to increase germination percentage.

Highlights:
1- Chilling period duration in the presence of gibberellic acid was the most important factor for the elimination of Schrophularia striata seed Dormancy and increased germination.
2- With increasing altitude and in the same chilling period duration, habitats with lower altitude had higher germination percentage and rate

Evaluation and Determination of the Salt Tolerance Threshold of Some Fenugreek (Trigonella foenum-graecum) Ecotypes at Seedling emergence Stage

Hamzeh Amiri

Extended Abstract

Introduction: Fenugreek, is a medicinal plant that has been considered as a salt tolerant crop. This research was conducted to investigate the effects of salt stress on seedling emergence characteristics and determination of the salt tolerance threshold, declivity of emergence and salt tolerance index of some fenugreek ecotypes.

Material and Methods: Seeds of five ecotypes (Ardestani, Isfahani, hendi, Mashhadi, Neyrizi) were subjected to seven levels of salinity (0.5, 3, 6, 9, 12, 15 and 18 dS/m) in a factorial experiment based on a completely randomized design with three replications. In this research, experimental models (linear, sigmoidal, exponential and multi-component) were used.

Results: Results showed that increasing levels of salinity decreased seedling emergence percentage and rate. In Ardestani and Isfahani ecotypes, increase of salinity up to 3 dS/m had no effect on seedling emergence percentage and thereafter, decreased it, significantly. The maximum seedling emergence percentage (94.62%) belonged to Hendi in control treatment. Hendi ecotype had also the highest emergence percentage (25.81%) at 18 dS/m. Although the highest seedling emergence rate (5.93 per day) belonged to Mashhadi ecotype in control treatment, it didn’t show any significant difference to Hendi, Neyrizi and Isfahani ecotypes. In Ardestani, Mashhadi and Neyrizi ecotypes, seedling length decreased significantly with increasing salinity, but this decrease was not significant in Isfahani ecotype between salinities of 3 and 6 dS/m and also 12 and 15 dS/m. In Hendi ecotype, seedling length at 3 dS/m was similar to control, but higher salinities caused a significant reduction. The maximum value of seedling vigor index (20.44) belonged to Mashhadi and Neyrizi ecotypes in control treatment and Ardestani ecotype had the lowest one (0.39) at 18 dS/m. Results showed that seedling dry weight was first unchanged up to salinity level of 3 dS/m and then gradually decreased with increasing salinity. In Hendi and Neyrizi ecotypes, applying salinities higher than 6 dS/m, gradually decreased seedling dry weight. The salt tolerance threshold of fenugreek for Ardestani, Isfahani, Hindi, Mashhadi and Neyrizi ecotypes was 4.69, 4.90, 7.83, 1.69 and 1.57 dS/m, respectively. Thus, the highest salt tolerance threshold (7.83 dS/m) and the declivity of emergence percentage (7.55%) was obtained from Hendi ecotype and the lowest one from Neyrizi ecotype (1.57 and 4.63 dS/m, respectively). Results of nonlinear models showed that the highest salinity in which 50 percent of seedlings emerged was obtained in Hendi ecotype (14.24 dS/m).

Conclusion: Based on the results, comparing the salt tolerance index of fenugreek ecotypes and also evaluating of some experimental models showed that Hendi ecotype may be introduced as the most tolerant ecotype to salinity stress at the emergence stage to exploit saline soil and water resources.

Highlights:

Different fenugreek ecotypes in terms of salinity tolerance at seedling emergence stage were compared using some experimental models.
The salt tolerance threshold, declivity of emergence and also salt tolerance index was reported for some fenugreek ecotypes.

Evaluating the optimization of irradiation components of mung bean seeds with ultrasound for increased seedling vigor, using artificial neural network

Manoochehr Gholipoor

Extended Abstract
Introduction: A large number of experimental evidence indicates the positive effect of irradiating the seed with ultrasonic waves; so that irradiation causes the production of a more vigorous seedling. Conversely, inappropriate intensity and duration of irradiation can impose deleterious effects on seedlings by damaging the enzymatic activity. There are complex inter-and intra-relations between irradiation components (pre-soaking duration, temperature, and duration of irradiation) and response variables [seedling dry weight (SDW) and percent of abnormal seedlings (PAS)]. Therefore the balance values of the irradiation components cannot be precisely obtained by mean comparison. This study aimed to optimize (finding the balance values of) irradiation components for increased SDW, but diminished PAS of mung bean, using an artificial neural network.
Materials and Methods: A factorial experiment was conducted based on a completely randomized design with three replications. The factors were six pre-soaking durations (2, 4, 6, 8, 10, and 12 hours), 5 irradiation durations (0, 3, 6, 9 and 12 minutes), and 4 irradiation temperatures (17, 22, 27, and 32 ^oC). The 25 seeds were chosen for each petri dish. The multi-layer perceptron neural network was used to quantify the relations between variables; the experimental factors were used as the input (regressors), and PAS and SDW as the output of the model (response variables).
Results: The analysis of variance results indicated that the simple and interactive effects of factors were significant on PAS and SDW. The structure 3:3:2 of the neural network, which is based on Secant Hyperbolic function, was suitable. The SDW and PAS were negligibly different for the contribution of the factors in determining their changes. In terms of relative contribution, the factors ranked from higher to lower as irradiation duration, irradiation temperature, and pre-soaking duration. The optimized values of components of irradiation by the neural network were irradiation temperature of 17.96 ^oC, irradiation duration of 5.3 minutes, and pre-soaking duration of 11.25 hours. For these components, SDW was 27% higher, and PAS tended to be 0.6% lower, compared to the best component combination gotten by mean comparison.
Conclusion: Due to the highly strong interaction of irradiation components on seedling growth, the effect of component (s) tends to be changed intensively with changing the quantity of each component. In terms of finding the best combination of irradiation components, the neural network was more efficient than the mean comparison. Therefore, the neural network could be used as a complementary procedure in such investigations.

Highlights:
1- Irradiation components including irradiation duration and temperature, and pre-soaking duration affected seedling growth.
2- Inappropriate irradiation components diminished seedling growth to the below of no-irradiation conditions.
3- The optimum (balanced) levels of irradiation components increased seedling growth remarkably.

Estimation of Cardinal Temperatures for Tomato (Solanum lycopersicom) Seed Germination Using Nonlinear Regression Models

Seyed Amir Moosavi

Extended Abstract
Introduction: Seed germination is one of the most important factors which determine the success of failure of crop establishment. In the absence of other environmental limiting factors such as moisture, temperature would determine the rate and overall seed germination. This research was conducted to investigate the effect of temperature regimes on seed germination, quantify the response of germination rate to temperature and determine the cardinal temperatures for different germination percentiles in Solanum lycopersicom.
Materials and Methods: Two-way factorial experiment including seven constant temperatures (5, 10, 15, 20, 25, 30 and 35 ^oC) and two tomato varieties (Red cherry: var. Cerasiformi and Yellow pearl: var. Yellow Pear) was conducted based on a completely randomized design arranged with thee replications at the seed technology laboratory of Agricultural Sciences and Natural Resources University of Khuzestan in 2019. Beta, segmented and dent-like functions were used to determine the relationship between germination rate and temperature. Logistic model was used to describe the suitable pattern for the germination of these two cultivars in response to each temperature level.
Results: Results of analysis of variance showed that the interaction effect of temperature and cultivar was significant on all studied traits. Results showed that respectively at temperatures of 15, 20, 25 and 30 ^oC, total seed germination for yellow pearl tomato was 93%, 96%, 95% and 86% and for red cherry tomato was 95, 98, 93 and 98 percent. There was no seed germination for both tomato varieties at 5, 10 and 35 ^oC. Based on the results of the fitted models, it was revealed that among the tested non-linear regression models, segmented model described the germination rate of the studied tomato cultivars against the temperature the best (AICc≤70, R²=0.93). Three parameters logistic functions exhibited a reasonable fit (R²=0.96) for germination time course under temperature range of 15 to 30 ^oC in both cultivars. Based on the segmented model, base, optimum and ceiling temperatures of Yellow pearl and Cherry tomato were estimated 11.25, 28.72, 35.00 ^oC and 10.97, 28.361 and 35 ^oC, respectively.
Conclusion: Both tomato cultivars exhibited sensitivity to changes in temperature. Seed germination rate and number of the germinated seeds increased at temperatures higher than base. This increase continued until the optimum temperature and then started to decline as the temperature exceeded from optimum range. Also, results obtained from the logistic function showed that Yellow pearl cultivar is more sensitive to supra-optimal temperatures compared with Cherry tomato, and germination percentage of the 97.79 to 85.09 percent as temperature reached from 25 to 30 ^oC.

Highlights:
1- The pattern of seed germination in two new tomato cultivars was investigated under temperatures regimes
2- Cardinal temperatures of two new tomato varieties was estimated using nonlinear regression models

The Effect of Seed Priming and Culture Medium Type on Germination Characteristics and Quality of Tomato Seedlings (Lycopersicon esculentum)

Mehdi Hosseinifarahi

Extended Abstract
Introduction: Today, seed priming is widely used to improve seed germination in a wide range of plant species. As a result of seed pre-treatment, several molecular and biochemical changes occur, including increased macromolecule synthesis, enzyme activity and formation of different metabolites. Enzymatic and metabolic activities, synthesis of proteins in quantitative and qualitative terms, and respiratory activities and, the formation of ATP for the synthesis of macromolecules, membranes, and materials required for the cell wall are increased during and after seed preparation. The aim of this study was to investigate the effect of seed priming using some hormonal and nutritional treatments as well as the type of culture medium on germination characteristics and quality of Karun tomato seedlings.
Materials and Methods: Two separate experiments were performed in two laboratory and pot stages in a completely randomized design with three replications. In the first experiment, the treatment used included seed priming at six levels (distilled water, 0.2 mM salicylic acid, 0.2 mM putrescine, 1.5% humic acid, 0.03% zinc sulfate, and 0.2 mM potassium nitrate). In the second experiment, the treatments used included the culture media type at six levels (coco peat, perlite, peat moss, 50% cocopeat + 50% perlite, 50% coco peat + 50% peat moss and 50% perlite + 50% peat-moss).
Results: Analysis of variance showed that the effect of different levels of seed priming on seed germination percentage and root length was significant. The highest germination percentage was obtained six days after cultivation in salicylic acid treatment and was equal to 97.1%. The highest shoot dry weight in peat moss treatment was 1.7 g and the lowest shoot dry weight in perlite treatment was 0.3 g. The use of peat moss treatment in comparison with coco peat increased seedling length by 31.3%.
Conclusion: Application of 0.2 mM salicylic acid, putrescine and humic acid improved seed germination compared with zinc sulfate and potassium nitrate. Also, application of peat moss and combined peat moss treatments in comparison with coco peat and perlite, increased the dry weight of roots and shoots of the plant as well as increasing the absorption of various elements.

Highlights:
1- Germination percentage and rate of tomato var. Karun significantly increased by salicylic acid and putrescine application (Karun cultivar)
2- Peat mass is the best culture medium for the commercial production of tomato seedlings var. Karun

Quantifying the Germination of Fagopyrum esculentum Moenc. Using Regression and Thermal-Time Models

Mohammdreza Amerian

Extended Abstract
Introduction: Germination is considered the first and most important stage of establishment and consequently, successful competition which is influenced by genetic and environmental factors. Among the environmental factors influencing the germination, temperature and light are the most important ones. Using different models, the germination response of seeds to temperature can be quantified; therefore, this study was performed to investigate the effect of temperature on germination and to quantify the germination response of Buckwheat seed (Fagopyrum esculentum Moenc) to temperature using nonlinear regression models and thermal-time model.
Materials and methods: The seeds were germinated in 4 replications of 25 seeds under 8 constant temperature treatments (5, 10, 15, 20, 25, 30, 35 and 40 ° C). Using a three-parameter logistic model, Buckwheat seed germination was quantified at different temperature levels and the percentage and time to reach 50% germination were obtained. Four nonlinear regression models and a thermal-time model were used to quantify the response of Buckwheat seed germination rate to temperature. To compare the models and determine the most appropriate model, the root mean square error index (RMSE), coefficient of determination (R²), coefficient of variation (CV) and standard error (SE) were used for the observed germination rate versus the predicted germination rate.
Results: The results indicated that temperature affected the seedling length, normal seedling percentage, seed vigor and the germination rate as well as germination percentage. Also, the results showed that germination characteristics increased with increasing temperature up to 20 and 25 °C. Comparison of the three models based on the root mean square error (RMSE) of germination time, the coefficient of determination (R²), CV and SE, the best model to determine the cardinal temperatures of Fagopyrum esculentum was the dent-like model. The results of thermal-time model showed that the base temperature of Fagopyrum esculentum seeds was 4.01 ° C and the thermal-time coefficient was 1242.6 h° C.
Conclusion: Utilization of non-linear regression models (segmented, dent-like and beta) and thermal-time model to quantify the germination response of Fagopyrum esculentum response to different temperatures led to acceptable results. Therefore, germination rate and percentage may be predicted using the outputs of these models at different temperatures.

Highlights:

The best temperature for Fagopyrum esculentum Moenc. seed germination is 20-25 Celsius.
The dent-like model was determined the most appropriate model for estimating the cardinal temperatures of Buckwheat.

Seed Dormancy: A Review on Importance, Dormancy Types and Elimination Methods, with Emphasis on the Trend of Seed Dormancy Research in Iran

Farshid Ghaderi-Far

Extended Abstract
Introduction: Seeds need successful germination at the optimal time and conditions to survive. Sometimes, even in the best environmental and genetic conditions of the seed, they do not germinate or germinate with a delay, which are called dormant seeds. Seed dormancy can have positive effects on avoiding adverse conditions and ensuring survival in the environment. However, dormancy in crop plants reduces emergence and yield by preventing germination. A combination of environmental and seed genetic factors are involved in seed dormancy formation. In general, seed dormancy includes: physical dormancy, physiological dormancy, morphological dormancy, morphophysiological dormancy and combinational dormancy, and physical / chemical scarification treatments, hot and cold stratification, leaching, hormonal treatments, after-ripening, light and combination treatments can be used to eliminate dormancy depending on its type. Therefore, in this study, using domestic studies conducted in the field of seed dormancy in different plant species, identification of dormancy in different plant species and its types have been discussed, and general and practical information in this regard has been provided.
Materials and Methods: In this study, 168 reports published on 250 plant species in the last 20 years, which were published in the seed dormancy of medicinal plants, weeds, rangelands, ornamentals and crops were investigated. Then, the percentage of plants studied and their families, as well as the share of different types of seed dormancy and appropriate treatments to for its eliminate were determined.
Results: Among the plant species studied, the most freuqent type of dormancy was related to physiological dormancy (50%), followed by physical dormancy, combinational dormancy, morphophysiological dormancy and the lowest share of dormancy in the studied plant species was related to morphological dormancy (1.61%). The most effective treatments to eliminate physiological dormancy were the use of cold stratification, gibberellic acid, and potassium nitrate. Also, the most effective treatments for the removal of physical dormancy were the use of physical / mechanical scarification treatments, chemical scarification and potassium nitrate treatment. According to the results, temperature treatments and then gibberellic acid and potassium nitrate treatments are recommendedt eliminate morphological dormancy. To eliminate morphophysiological dormancy, it is recommended to use treatments to maturate differentiated small or undifferentiated seeds (removal of morphological dormancy) as well as treatments to counteract the germination inhibitory factors or to compensate the were applied the most to eliminate morphophysiological dormancy.
Conclusion: By identifying the type of dormancy and applying the appropriate treatments, the germination of economical and valuable plants can be improved.

Highlights:
1- Dormancy types in native plant species of Iran through the information of domestic studies was investigated and a comprehensive report on seed dormancy was presented for the first time.
2- General and practical information about seed dormancy, effective factors and methods of dormancy elimination was reviewed in a practical way.

Evaluating the Germination Indices of Different Genotypes of Sesame Plant (Sesamum indicum) Under Salinity Stress

Seyyed Kamal Kazemitabar

Extended abstract
Introduction: One of the ways to overcome the limitation of fresh water and lack of sufficient water reserves for agriculture is to use unconventional waters such as seawater. Salinity stress is the most important abiotic stress in seawater application. Identification and planting of salinity tolerant genotypes of a plant species is one of the effective and valuable strategies in reducing the effects of salinity stress. Germination, growth and seedling establishment are among the salinity-sensitive stages in most plants. Therefore, for improvement of abiotic stress tolerance in plants, it is necessary to study the traits and indicators related to tolerance in the germination stage.
Material and Methods: A factorial experiment was conducted based on a completely randomized design with three replications at the laboratory of Plant Breeding Department of Sari University of Agricultural Sciences and Natural Resources in 2020. The first factor included the cultivars and the second included 5 salinity levels (control (no seawater), 3, 6, 9 and 11 dS (deciSiemens per meter) obtained from the incorporation of Caspian Sea and urban water. The number of germinated seeds was counted during eight days of salinity stress. Then, germination percentage, time required for 50% germination, seedling vigor index and germination rate were calculated. On the eighth day, radicle and plumule dry and fresg weights, radicle and plumule length and seedling dry weight were measured.
Results: The results of analysis of variance showed the significance of the effect of different salinity levels, genotype and the interaction of salinity and genotype for all calculated indices at p<0.01. Mean comparison of the interaction of different levels of salinity and cultivars and landraces showed that all the studied traits except for the time to reach fifty percent germination decreased with increasing salinity. Among the studied cultivars, Oltan cultivar had the highest value of germination percentage (100%), germination rate (24.17 seeds per day), seedling vigor index (5.03), plumule length (55.67 mm), radicle length (70 mm), plumule fresh weight (62 mg), radicle fresh weight (45 mg), plumule dry weight (4.77 mg), seedling dry weight (6/23 Mg) and the lowest amount of the time required for 50% germination (24.17 hours) in control treatment. In contrast, Pakistani cultivar had the lowest germination rate (3.06 seeds per day), seedling vigor index (1), plumule length (8.33 mm), radicle length (3 mm), plumule fresh weight (10 mg), radicle fresh weight (2 mg), plumule dry weight (0.57 mg), seedling dry weight (0.84 mg) and the highest time required for 50% germination (24.17 hours) in 11 dS / m salinity level. Using the results of this experiment, among the studied cultivars, Oltan cultivar was selected as the most tolerant and Pakistani cultivar as the most sensitive cultivars to salinity stress at the germination stage.
Conclusion: The studied cultivars and landraces showed different reactions in terms of germination indices when treated with salinity from seawater. The high significant difference in this experiment indicated the high genetic diversity among the studied genotypes. It is possible to choose from these genotypes for salinity tolerance breeding programs in sesame plant.

Highlights:

Different sesame genotypes at different levels of sea salt salinity showed different response at germination stage.
Among the cultivars studied, Oltan, Nazetakshakhe, Halil and Dashtashtan 2 showed a high degree of tolerance to salinity stress.

The Effect of Different Pretreatments on Seed Dormancy Elimination and Seed Germination Improvement of Guava (Psidium guajava)

Maryam Boroujerdnia

Extend abstract
Introduction: Guava (Psidium guajava L.) is one of the most important fruit crops of tropical and subtropical regions. Guava (Psidium guajava L.) can be propagated by seed, layering, grafting, cutting or tissue culture. Propagation by seed is used for the production of seedlings usable in breeding programs or rootstock production for grafting. Guava seeds germinate poorly and unevenly and require more time for seedling emergence. The dormancy in seeds might be due to hard seed coat and different methods are used for breaking dormancy in seeds to improve germination. The aim of this study was to evaluate efficiency of the different pretreatment on seed dormancy breaking and germination characteristics of guava.
Materials and Methods: The experiment was laid out in a completely randomized design with three replications on guava seeds in genetic and breeding laboratory of Date Palm and Tropical Fruit Research Center at the summer of 2018. Treatments consisted of distilled water (24 and 48 h), 0.5 and 1% potassium nitrate (KNO₃) for 24 h, warm water (70 ° C) for 5 and 10 min, 25% and 50% sulphuric acid for 5 min, and control (non-treated). In this study, the traits of germination percentage, germination rate and mean of daily germination, seed vigour index and fresh weight and length of seedling were measured. Data analysis was done using the SAS 9.2 software and the Duncan's test at 5% probability level was used for mean comparison.
Results: Results showed that the effect of treatments on seed germination indices (germination percentage, germination rate and mean of daily germination, seed vigour index) of guava was significant at p<0.01. The greatest germination percentage (53.1%), germination rate (6.6 seed/day) and seed vigour (2636.7) were observed in treatment of 1% potassium nitrate (KNO₃) for 24 h. The lowest Mean time to germination (14 days) was obtained in distilled water for 48h. Warm water treatments at 70 °C and 25% and 50% sulfuric acid were not effective in improving seed germination compared to control. The highest seed length and weight were observed in 1% potassium nitrate and 0.5% potassium nitrate pretreatments, respectively.
Conclusions: the results of this study show that among the different treatments, pre-treatment of seeds with 1%potassium nitrate may be considered as an effective way to improve seed germination of guava. Also, pretreatment with distilled water for 48 hours is an easy, low cost and effective way to increase guava seed germination indices.

Highlights:
1- The effect of different chemical treatments on germination characteristics of guava was investigated.
2- The suitable method for seed dormancy elimination and seed germination improvement of guava was introduced.

The Improvement of Cow Tail (Smirnovia iranica) Seed Germination through in vitro Culture

Nasim Zarinpanjeh

Extended Abstract
Introduction: Cow tail (Smirnovia iranica) is considered a valuable shrub species indigenous and adapted to the sandy lands of the Iranian central regions which besides playing an essential role in the desert cover for soil protection and of forage production, is considered important due to its great medicinal values. Considering the fact that seed germination of this plant does not easily occur due to its hard and solid seed coat, in this study, the in vitro tissue culture and seedling establishment is utilized for the first time in order to surmount the obstacles laid ahead of cow tail seed germination.
Materials and Methods: Scratched seed, unscratched seed and seed embryo of cow tail as different explants were placed in two culture media (MS, MS with free amino acids complex) following surface sterilization, and were exposed to two photoperiod treatments (16 hours of light and 8 hours of darkness as well as absolute darkness) and were investigated in a factorial experiment based on completely randomized design with six replications. Finally, germination percentage (10 days after seed culturing) and shoot length (30 days after seed germination) were evaluated.
Results: The results indicated that significance of the effect of investigated treatment conducted over some in vitro on germination characteristics. It was revealed that the cultivation of seed embryo in MS culture media along with free amino acids complex for 16 hours of light and 8 hours of darkness photo period can be considered as the best in vitro germination method, in terms of seed germination percentage (78.83%) and germinated shoot length (44.83 mm).
Conclusion: In vitro culture can be used to improve germination and seeding production of this species.

Highlights:

The method for seed dormancy elimination of cow tail plant was introduced.
The seed disinfection procedure for in vitro culture of cow tail plant was introduced.
The components of in vitro culture medium for rapid and efficient seed germination of cow tail plant were introduced.