جستجوی مقالات مرتبط با کلیدواژه « برنج » در نشریات گروه « زراعت »

This study was performed to evaluate the effect of Rahnella aquatilis and Burkholderia cepacia bacteria on yield, yield components, and uptake of potassium and zinc elements in rice (Oryza sativa L.).

The experiment was conducted as a split-plot in a randomized complete block design with three replications in 2022. Treatments included two levels of chemical fertilizer (100 and 75% of chemical fertilizer consumption based on the soil test results as optimal and reduced fertilizer levels, respectively) and four inoculation treatments (separate inoculation of R. aquatilis, B. cepacia, a co-inoculation (R.aquatilis+B.cepacia) and control (non-inoculation)).

The results indicated that there was no significant difference between the optimal and reduced fertilizer levels in all the studied traits. The separate inoculation of R. aquatilis, B.cepacia and their co-inoculation increased the panicle length (from 5.88 to 11.3%), the number of total tillers in hill-1 (from 19.4 to 29.1%), the total number of grains in panicle-1 (from 22.8 to 46.5%), paddy yield (from 22.8 to 44.3%), biological yield (from 20.3 to 33.6%), 1000-seed weight (from 2.4 to 8.8%), potassium uptake in grain (from 6.0 to 41.4%) and in above-ground biomass (from 38.4 to 65.4%), zinc uptake in grain (from 6.29 to 40.9%) and in above-ground biomass (29.4 to 54.6%) as compared with the control (non-inoculation).

The application of plant growth-promoting rhizobacteria in combination (as the best inoculation treatment) reduced chemical fertilizers consumption without a significant reduction in the paddy yield, indicating the importance of these rhizobacteria for achieving sustainable agriculture goals.

Salinity stress is a very serious threat to most agricultural products in the world. In the world, rice ranks second after wheat and is a relatively sensitive plant to salt stress. Protein kinases are an important group of kinase enzymes that phosphorylate target proteins by adding phosphate groups. These enzymes play an important role in cell communication by inducing the message of growth and reproduction. Gene expression is a process during which a useful gene product is synthesized by the information obtained from a gene. The purpose of this research was to investigate the expression level of SAPK1 gene from the protein kinase gene group in rice plants under sodium chloride salt stress by examining three different times after the stress was applied In this study, the expression pattern of SAPK1 gene in two Cultivars tolerant (Shastak Mohammadi) and sensitive (IR29) of rice plant under salt stress was investigated by factorial experiment in the form of a completely randomized design with three replications. Cultivars were planted in the research greenhouse of the Faculty of Agriculture of Lorestan University and at the seedling stage (5 to 6 leaves), salinity stress was applied to the plant at three levels of 3, 6, and 9 dS/m and the control treatment (without salt stress). Then, at three different times (6, 12, and 24 hours after applying stress), plant leaves were sampled to investigate gene expression. The leaf samples were stored in a freezer at minus 80 degrees Celsius. Then, RNA extraction and cDNA synthesis were done by special kits for each stage, and finally, The results of the analysis of SAPK1 gene expression pattern showed that in both tolerant and sensitive cultivars, the highest level of gene expression was observed at the salinity level of 9 ds/m 24 hours after applying the stress. At different times after applying the stress in the control treatment and the salinity level of 3 ds/m, the gene expression level in both tolerant and sensitive cultivars did not show any difference and was very insignificant. However, at the salinity level of 6 ds/m, 6 hours after applying the stress, the gene expression level in the tolerant cultivar increased 3 fold compared to the sensitive cultivar and control treatment. At this level, examining gene expression 12 and 24 hours after applying the stress, the amount of gene expression in the tolerant cultivar was about 7 fold higher than the sensitive cultivar and the control treatment. At the salinity level of 9 ds/m, 6 hours after applying the stress, the gene expression level in the tolerant cultivar was doubled compared to the sensitive cultivar and 4 fold higher than the control treatment. While 12 hours after applying the stress, the gene expression level in the tolerant cultivar increased by 5.5 fold compared to the sensitive cultivar and by 10 fold compared to the control treatment. Also, 24 hours after applying the stress, gene expression in tolerant cultivar was 3.5 fold higher than the sensitive cultivar and 11 fold higher than the control treatment. These results showed that the expression of SAPK1 gene increases in rice plants with increasing salinity levels. nvestigating the effect of time after applying stress on SAPK1 gene expression, it was found that in the early hours after applying stress, the amount of gene expression was low, but with increasing time up to 24 hours, gene expression in tolerant cultivar increased These results can be used in molecular studies of rice cultivars to select the most tolerant rice cultivars to salinity stress for cultivation in areas prone to salinity.

One of the important goals of rice breeding programs is to develop new high yielding cultivars with high quality properties as well as desirable agronomic traits. Introducing of such cultivars and adoption them by farmers will lead to increased production. This experiment evaluated new hybrid rice cultivars under different transplanting bed methods in the Khuzestan climate conditions in Iran.

The experiment was carried out as split plot arrangements in randomized complete block design with three replications in 2020-2021 and 2021-2022 growing seasons at the Shaawor agricultural research station, Ahvaz, Iran. The main plots were wet and dry transplanting bed methods, and the sub-plots consisted of seven hybrid rice cultivars (L66S, F168S, Quan2, XinerPS, Hs–3, Shen51S and Hui34S). SPAD value, leaf area index (LAI), number of tillers, growth duration, panicle fertility, plant height, grain yield and yield components and biological yield were measured.

The results indicated that the SPAD value, leaf area index, number of tillers, growth duration, panicle fertility, plant height, grain yield and yield components and biological yield were significantly affected by the interaction effect of year × transplanting bed × cultivar. SPAD value, LAI, number of tillers, growth duration, panicle fertility, plant height, yield components and grain yield and biological yield were higher in wet bed transplanting method. Also, Quan2S and Hui34S hybrid cultivars were superior than the remaining five hybrids. in 2021, the tallest plant height (84.3 and 81 cm) and LAI (4.3 and 4.2), the greatest number of grains per panicle (189 and 160), and the weight of 1000 grain weight (24.4 and 25.8 g) were observed in Quan2S and Hui34S cultivars, respectively, in wet bed transplanting method. However, in 2022, most of the studied hybrid rice cultivars did not show significant differences. The highest grain yield (5200 and 4675 kg.ha-1) and biological yield (12380 and 10143 kg.ha-1) were obtained from Quan2S and Hui34S hybrid rice cultivars, respectively, in the 2021 and wet bed transplanting. The results of cluster analysis showed that seven hybrid rice cultivars were separated into three different groups. The first group comprised XinerPS, L66S, and F168S, the second group included Hs-3 and Shen 51S and third group comprised Quan2S and Hui34S hybrid rice cultivars.

The results of this experiment showed that while the hybrid rice cultivars did not perform successful and are of low adaptability in Khuzestan environmental conditions. The results also indicated that wet bed transplanting method is suitable for Khuzestan environmental conditions and led to higher grain yield of rice hybrid cultivars.

Increasing rice production is one of the demands of the world market and one of the goals of many countries that produce this staple crop. Development of high yielding cultivars is one approach and perhaps the only one to supply the country's rice demand. Knowledge of the genetic parameters that control different traits, including heritability, the average degree of dominance, and gene action is very important in choosing a breeding scheme that lwads to development of improved high yielding cultivars. The diallel designs proposed by Griffing, Jinks, and Hayman provide information about the genetic suitability of parents to be used in breeding programs. This experiment was carried out to estimate the combining ability and the type of gene action of eight Central and Western Asian rice varieties using diallel crossing design.

In this experiment, eight rice varieties from Central and West Asia were used as the parents of the crosses. The progenies obtained from the diallel crossing design along with their parents were grown using randomized complete block design with three replications in the experimental field of Rice Research Institute of Iran, Rasht, Iran. During the growth duration, according to the standard evaluation method of the International Rice Research Institute (IRRI), the necessary evaluations for agro-morphological characteristics were carried out. Diallele analysis was performed using the second Griffing method under the first model (with fixed effect). Baker's ratio was used to determine the contribution of additive variance in the genetic control of studied traits. Also, diallel analysis proposed by Morley Jones method done to estimate gene actions and genetic variance components (additive and dominant). SAS 9.4 and DIAL98 softwares were used to perform preliminary variance and diallel analysis.

The results of diallel analysis by Griffing method to estimate combining ability showed that general and specific combining ability were significant for all studied traits which indicated the importance of additive and non-additive effects in the genetic control of these traits. Baker's ratio for grain yield, number of fertile tiller number per plant and number of filled grains per panicle showed that non-additive gene effects had a significant contribution in the genetic control of these traits. The value of Baker's ratio in plant height, panicle length and number of days to 50% of flowering indicated the presence of additive and non-additive gene effects in the genetic control of the aforementioned traits. Evaluation of general combining ability showed that the highest combining ability was observed in D3, Ghadeer, Atai-1 and Hashemi cultivars for grain yield, fertile tiller number per plant, filled grains per panicle and panicle length, respectively. Also, D3 and Marjan cultivars had the lowest general combining ability for plant height and days to 50% of flowering. The estimation of specific combining ability showed that for grain yield, Atai-1×Marjan cross, for fertile tiller number per plant, Ghadeer×Atai-1 cross, for filled grains per panicle, Marjan×Atai-1 cross and for panicle length, Ghadeer×Marjan cross had the highest specific combining ability. The estimation of genetic parameters of diallel genetic analysis showed that the contribution of non-additive gene effect in the genetic control of grain yield, fertile tillers per plant, plant height, filled gains pe panicle and panicle length was higher than additive gene effect.

considering the resuts of this experiment, it can besuggested that D3 cultivar is suitable parent for increasing grain yield as well as reducing plant height, and Marjan cultivar is suitable parent for shortening growth duration, in targeted crosses. The results also showed that Atai-1×Marjan cross had the highest specific combining ability for grain yield. Therefore, this combination is suggested for the development of high yield potential hybrid rice cultivars. The best combination for shorter plant height was Jalal×Atai-1 cross. The estimation of genetic parameters of diallel analysis showed that designing breeding schemesfor development of hybrid rice cultivars to improve grain yield and reduce plant height will be promising. The results also indicated that the use of selection method to reduce the length of growth duration will be possible.

Creating semi-dwarf plants is one of the most important goals in rice breeding. The decrease in the quality and quantity of the  crope produced due to the dormancy of the rice plant has a negative effect on the farmers' economy. In order to stabilize the cultivated area and also to supply rice for the country's consumption, it is recommended to introduce cultivars of local origin with semi-dwarfing traits, along with increasing yield. The first step to transferring this trait to local cultivars is screening to identify suitable parents for transferring the semi-dwarf gene and also identifying efficient markers for the advancement of backcrossing projects with the help of markers. For this purpose, this research was carried out for the phenotypic evaluation and molecular screening of the available genotypes based on the functional markers related to the semi-dwarfing trait.

In this research, 50 local and improved rice genotypes were prepared from the collection of the Rice Research Institute of Iran And the dwarfing trait was investigated based on phenotypic and molecular evaluations in the field related to the band pattern created by a pair of specific primers (semidwarfing gene = sd1) contiguous with the gene locus controlling the semi-dwarfing trait. The generalized linear logistic regression model was used to analyze the observed correlation between genes. Also, the hypothesis of  a genetic relationship between the sd1 gene allele and plant height was tested through a logistic regression model.

Based on the genetic evaluation, 26 cultivars were found to have the allele of the semi-dwarfing gene and 24 cultivars did not have the allele of this gene, and the used marker is able to predict and differentiate the  cultivars for future breeding  programs with high confidence and accuracy. The logistic regression results also confirmed this result.

According to the observed results, the used functional marker sd1 can be used as an efficient marker for the screening of separating populations to improve the semi-dwarfing trait.

Rice (Oryza sativa L.) feeds more than half of the world's population. Rice is considered a model plant in biological and agriculture field research due to its small genome compared with other plants. Storage proteins in the aleurone layer of rice seeds include albumin and globulin, as well as the endosperm, prolamin, and glutelin proteins. To determine the number of proteins and identify the protein spots between the tissues of two embryo samples and rice endosperm, the protein spots were matched according to their expression level in the images obtained from two-dimensional gel electrophoresis.
The profile of proteins in the endosperm and embryo of rice seeds was determined using isoelectric focusing (IEF) and polyacrylamide gel electrophoresis(SDS-PAGE) methods. The Image Master software was utilized to analyze the two-dimensional gels. Considering the importance of local rice consumption in Iran and the significant production of this economically important crop in the country, this study aimed to determine the diversity and differences in the expression of protein spots within the linear pH range of 4 to 7. The two-dimensional electrophoresis method was employed on the Hasan-Sarai variety of rice indigenous to the region of Guilan. For this research, the cultivar being examined was procured from the Guilan Rice Research Center. Subsequent stages of the experiment, including sample separation and total protein extraction, were conducted at the Payame Noor University laboratory in Asadabad. Ultimately, the protein samples obtained were sent to the Health Research Institute at the Faculty of Pharmacy, where two-dimensional electrophoresis was carried out using an isoelectric focusing device. Finally, the extracted protein samples were transferred to the Health Research Institute of the Faculty of Pharmacy to perform two-dimensional electrophoresis using an isoelectric focusing device.
Based on the results of the two-dimensional gel analysis, a large part of the protein spots are present in the pH range of 4 to 7. The analysis of protein profile based on standard proteins with specific molecular weight and isoelectric point indicates that embryo tissue and endosperm based on isoelectric point and molecular weight showed that 284 protein spots in the embryo and 123 protein spots in endosperm have been identified. Among the identified spots, 57 common protein spots showed increased and decreased expression between the two samples. The presence of remaining protein spots in the two samples showed a significant difference between protein content in the embryo and endosperm.
Image master software was used to determine the isoelectric point and molecular weight of protein spots and expression changes between common spots. Analysis was done in protein databases and possible proteins were identified in embryo tissue and endosperm. The proteins identified in rice endosperm and embryo tissue in two-dimensional electrophoresis included grain storage proteins, glutelin precursors, acidic and alkaline glutelins, globulins, prolamins, HSPs, and hypothetical proteins. Therefore, in this way, it is possible to identify the level of expression of proteins and also their biosynthetic pathways.

Seed germination and emergence are the most sensitive stages of growth and development of rice plants. In this regard, the use of growth-promoting fungi in the form of seed biological pretreatment (bio-priming) for germination and optimal growth of seedlings can be feasible. Therefore, this study aimed to investigate the effect of isolated root symbiotic fungi on the improvement of germination and growth components of two traditional and bred rice (Oryza sativa L.) cultivars.

This experiment was done as a factorial-based completely randomized design with three replicates at Sari Agricultural Sciences and Natural Resources University in the summer of 2021. Experimental treatments included 22 isolates of root symbiotic fungi (isolated and identified from previous experiments) and control (without inoculation) and two native (Hashemi) and bred (Roshan) rice cultivars. After the end of the germination period, the number of normal seedlings was counted and five normal seedlings were randomly selected to measure the length of the root, stem, and seedling as well as the fresh and dry weight of the root, stem, and seedling.

Based on the results of cluster analysis the fungi were divided into four and three groups in Roshan and Hashemi cultivars, respectively. In both cultivars, group I was selected as the best group. In this group, the highest positive effect on vegetative traits varied from 5 to 59% compared to the control in fungal treatments was related to Bjerkandera adusta (ST1), Trichoderma atroviride (SF1), Monosporascus cannonballus (B3) and Trichoderma atroviride (SN1) in Roshan cultivar and Bjerkand adusta (ST1) in Hashemi cultivar. The best fungal treatments in germination traits of Roshan and Hashemi cultivars were Chaetomium globosum (SE2) and Bjerkandera adusta (ST1), respectively.

Overall, the results indicated the positive effect of most symbiotic fungi on the growth and germination characteristics of rice in both Roshan and Hashemi cultivars. These results show that symbiotic fungi use different mechanisms to increase growth and improve germination indicators in plants.

Highlights:

1- Growth-promoting fungi in the form of seed biological pretreatment were used (bio-priming) for optimal growth and germination and of rice seedlings.
2- The effect of native fungi isolated was investigated for the first time in two native (Hashemi) and bred (Roshan) rice cultivars.

Soil salinity is one of the environmental stresses that causes the accumulation of reactive oxygen species (ROS), and oxidative stress, and consequently, reduces crop growth and production. Antioxidative mechanisms are critical to protect cells from the adverse effects of ROS.

Thhis study was conducted in nutrient solution in Rice Research Institute of Iran, Rasht, Iran in 2019. The enzymatic activity and expression of effective genes on antioxidant defense were examined in two selected mutant genotypes (em3hs290 and em3hs84) tolerant to salinity stress, with Hashemi local cultivar, FL478 (tolerant) and IR28 (sensitive) genotypes. Biochemical traits including the activity of antioxidant enzymes, peroxidase, catalase, and ascorbate peroxidase, and the relative expression of genes encoding transcription factors (SNACI, DREB2B, and DREB2A) and genes associated with oxidative stress (OsAOX1C ،POX1، OsGR1، OsAPX2 and OsGPX1) were also measured and detected using real-time PCR technique.

The results showed that enzymatic activity of peroxidase (POX) in control cultivars (cv. Hashemi and IR28 cultivars) and ascorbate peroxidase (APX) in tolerant mutant genotypes and FL478 cultivar increased significantly. The genes expression associated with salinity stress tolerance also indicated that despite the variable behavior of the genes in the studied mutant genotypes, the expression of OSGR1, DREB2B, OsAOX1C and POX1  genes in studied tolerant mutants was more than susceptible cultivar. Transcript abundance of the OsAPX2 gene was significantly higher in salt-tolerant genotypes under short-term salinity stress and correlated with peroxide hydrogen removal and increased activity of ascorbate peroxidase enzyme.

The lack of similarity in the expression pattern of studied genes between the two salt-tolerant mutant genotypes (em4hs290 and em4hs84)  and  cv. Hashemi showed that the mutation could triger the salt-tolerance mechanisms in mutant genotypes, in comparison of cv. Hashemi, through emhancement of antioxidant enzymes activity in response to salt stress. It seemes that the mutant genotypes may have suitable growth in soil salinity conditions.

In order to compare the quantitative and qualitative characteristics of two tall rice cultivars under different planting systems, an experiment was conducted as a split-plot in a randomized complete block design with four replications at the farmer's field located in Neka during 2021-2022. The rice cultivars at two levels (Tarom Hashemi and Sange-Tarom) as the main plot and the planting systems at three levels (traditional planting, improved planting and system of rice intensification (SRI)) as the sub-factor were considered. The results showed that the Tarom Hashemi cultivar (3371 kg.ha-1) and Sange-Tarom (3448 kg.ha-1) were in the same statistical group in terms of grain yield, but the nitrogen concentration in rice grains for Tarom Hashemi (1.49%) was significantly higher than Sange-Tarom (1.39%). The plants cultivated in the SRI produced the highest grain yield with an average of 3736 kg.ha-1, which showed an increase in yield by 14.9% and 11.3%, respectively, compared with the traditional and improved planting systems. The use of SRI management led to the production of the highest concentration of nitrogen in the grain (1.63%) and the application of the improved planting system resulted in the accumulation of the highest concentration of phosphorus (0.15%) and potassium (0.47%) in the rice grain. Therefore, according to the results of the present research, the use of SRI management system increases the quantitative and qualitative characteristics and sustainable production of rice.

Butomus is an aquatic weed belonging to the butomaceae family, which has invaded the paddy field ecosystem in recent years. This study was carried out in order to investigate some eco-physiological aspects and chemical management of butomus in paddy field. In the field studies; the emergence time, height, tillering, flowering, and life cycle of butomus in the paddy field ecosystem and the germination rate of bulblets in the laboratory and the effectiveness of pre-emergence and post-emergence soil-applied herbicides in pot experiments, and also foliar-applied herbicides were investigated. The results revealed that waterlogged lands are the main habitat of butomus, and the bulblets are the main reproductive organs of this weed. While puddling, about 100% bulblets are separated from the rhizomes which floated on the water and dispersed. Both rhizomes and bulblets of butomus were submergence tolerant and germinated from 15 cm or more of submergence. Flowering of butomus preceded about one week the initiation of rice panicle. Each plant produced dozens of flowering tillers taller than rice stalk, hundreds of spindle-shaped bulblets up to 25 mm long, with more than 95% emergence rate. In pre-emergence application, soil-applied herbicides including clomazone+pendimethalin, oxadiargyl, pretilachlor, pendimethalin, and thiobencarb, controlled butomus less than 65% and sulfonylureas herbicides; pyrazosulfuron, metazosulfuron, flucetosulfuron, and bensulfuron methyl provided more than 85% control of butomus. The effectiveness of sulfonylureas in the post-emergence application was around 10% lower compared with pre-emergence application. Foliar applied herbicides; penoxsulam and propanil controlled butomus 62% and 70% and its control by bispyribac sodium, penoxsulam+cyhalofop-butyl, bentazon+MCPA, and pyribenzoxim were 80, 86, 89, and 99%, respectively. Therefore, it is recommended to apply a soil-applied sulfonylurea or a foliar-applied herbicide in the paddy fields infested with butomus in addition to the specific herbicide for barnyardgrass control.

Rice (Oryza sativa L.) is one of the most important cereals which known to have high nutritional value in foods population worldwide. Rice sheath blight is considered as a critical diseases and Rhizoctonia solani (Teleomorph: Thanatephorus cucumeris) is the causal agent of the disease. Induction of resistance by chemical compounds is a very interesting alternative approach in plant disease management. Various biotic and abiotic factors have a role in activation of resistance genes expression in plants. Potassium phosphite is among the chemical compounds which is able to induce of resistance genes in plants and leads to suppression of diseases by directly affecting the pathogens and indirectly by stimulating the host defense responses. In this study, the effects of potassium phosphite application was considered on the expression of some pathogenesis related genes in both Tarom (Resistance) and Khazar (susceptible) cultivars in challenging with R. solani.

The factorial experiment completely randomized design was used in this research. The effect of Potassium phosphite on Tarom (Resistance) and Khazar (Sensitive) rice cultivars in challenging with R. solani was considered. Four weeks old rice treated with potassium phosphite and as well mock plants were infected with the disease causal agent, R. solani. The sampling carried out at 0, 24, 48, 72 and 96 hours after infection. After total RNA extraction and cDNA synthesis, real-time quantitative PCR was performed to studying the expression pattern of PAL, LOX, PR1, PR3 and PR5 genes using specific primers.

In this research, findings demonstrated that there is a significant increase in the expression of PAL, LOX, PR1, PR3 and PR5 genes in potassium phosphite treated rice when compared to the mock plants. The effects of the treatments in all traits in the expression level of LOX, PR1, PR3 and PR5 genes were significant, but in the expression level of the PAL gene, in the treatment-cultivar and treatment-cultivar-time traits were not significant. Nevertheless, for the other traits it was significant. Between the Tarom (Resistance) and Khazar (Susceptible) cultivars, except for the PR1 gene, there was a significant difference in the rest of mentioned genes. As well, between the treatments, all five genes had a significant mean comparison.

These findings show that potassium phosphite causes a rapid and intense response of the rice plant against R. solani through the induction of different genes and leads to increase in sheat blight disease resistance. Actually in Tarom cultivar, resistance genes were expressed faster and further than Khazar cultivar.

Heat and its effects are considered one of the serious threats and damages to the production of agricultural and horticultural crops in many regions of the world. Therefore, it has led to pervasive changes in terms of morphological, physiological, anatomical, and molecular, which causes a sharp decrease in the economic performance of agricultural products. Nowadays, in order to reduce these inhibitory effects, in addition to classical and conventional breeding methods, modern and molecular methods can be used to identify heat-tolerant genes and use them in breeding programs to improve plant tolerance to environmental stresses.

The selection for heat tolerance among four local cultivars Hovyzeh, Hamar, Red-Anbori, Champa and three promising heat tolerant lines V1, V2 and V3 obtained from the international breeding programs of Khuzestan Agricultural Research and Training Center and Natural Resources were evaluated by osHATS and HSP70 genes qPCR on two experimental cultivation dates: May 20 (unfavorable) and June 20 (favorable) 2022 in Ahvaz.

The results obtained from the analysis of gene expression by qPCR on the date of the first cultivation confirmed the presence of the osHTAS gene in rice varieties and lines so that the local variety Champa, Hovyzeh, and line V2 has a high relative gene expression compared to other varieties and lines studied and they were significantly different from each other. The analysis of the osHTAS gene expression on the second planting date (June) in Ahvaz also shows the presence of the high-temperature tolerance gene in Hovyzeh, Hamar and V2 lines; therefore, the mentioned varieties could be used as parental lines for transfer heat tolerance gene to be used in multi-breeding programs and terms of the relative expression level of the gene, they showed a statistically significant difference with each other. The results of the relative gene expression of the HSP70 gene in the cultivation date of May showed that the local cultivars Champa, Red-Anbori and Hovyzeh had a remarkable superiority over the others. Examining the HSP70 gene expression pattern of rice cultivars and lines on the second planting date also revealed that the local cultivars Red-Anbori, Champa, Hovyzeh, and Hamar showed superiority. The tolerance of local cultivars to heat stress is due to their rapid growth and the creation of a large green cover in the early stages of growth, and their great adaptation to the region's environmental conditions.

Local cultivars can withstand heat stress well with rapid growth and creating much vegetation due to their high adaptability to environmental conditions and the presence of heat stress tolerance genes. They could be used as parental lines in breeding programs.

The use of seeds to create genetic mutation brings problems because the use of seeds increases the duration of the research, and the study of traits requires plant cultivation, making it impossible to test more than once a year. Another point is the presence of shimmer in mutant plants. Biotechnology techniques, especially tissue culture, solve these problems today. In this method, a repeatable and efficient regeneration system is needed to create mutations in rice plants to obtain fertile plants from the changed tissues.

To determine the appropriate dose of mutation induction to create genetic changes in the callus tissue obtained from the mature and immature embryos of Nemat and Taram rice varieties, a factorial experiment was carried out within a completely randomized design using doses of 20, 30, 40, 50 and 60 Gy (GY) of Gamma radiation in four replications. For callus generation, MS medium with 0.5 mg/liter 2, 4-D and 1 mg/liter Kasein was suitable for both cultivars. Also, for the regeneration of calluses obtained from both types of embryos of the Tarom cultivar, MS base medium containing 4 mg/liter of BAP, 0.5 mg/liter of IAA, 0.5 mg/liter of NAA, and 5 mg/liter of Kasien were used. In the final stage, 30-day-old calluses were subjected to gamma radiation treatment with five doses of 20, 30, 40, 50 and 60 Gy. They were compared with the control treatment in the regeneration stage regarding moisture percentage, growth rate and regeneration percentage.

After irradiation, the effect of variety on regeneration percentage, growth rate based on weight and callus diameter, the effect of embryo type on regeneration percentage and moisture percentage, the effect of radiation on all studied traits, the effect of variety × embryo only for regeneration percentage and moisture percentage, the effect of variety × radiation for all traits and the effect of embryo × radiation and cultivar × embryo × radiation were significant only for the percentage of reproduction. The LD50 obtained in Nemat and Tarom cultivars with mature embryos was related to doses of 26.78 and 41.83 Gray, respectively; with immature embryos, it was 14.55 and 35.30 Gray, respectively.

The difference in this experiment can not only be caused by genetic differences, but it can also be due to the difference in callus humidity and the effect of gamma rays.

Cultivar Tolo (AN74) was originated from a cross made between Ali-Kazemi as a local and Nemat as an improved rice cultivars. A set of 45 pure rice breeding lines including AN74 was selected through preliminary observational evaluation of RILs populations, followed by an observational yield trial which was conducted in an augmented design in 2011. Later on, 11 selected lines including AN74 were evaluated in a replicated yield trial in 2012. Then, seven selected advanced promising lines including AN74 were tested in a multi location trial together with four check varieties including Nemat, Tarom-Mahalli, San-Huan-Zhan2 (SHZ2) and Shiroudi in four locations of Tonekabon, Amol, Babol and Behshahr in three consecutive years. Stability analysis through Additive Main effect and Multiplicative Interaction (AMMI) indicated that Tolo (AN74) had relative general but specific adaptability to all and central parts, such as Amol and Babol in Mazandaran province. The main characteristics of Tolo cultivar are early maturity with days to 50% of flowering of 78 ± 5 days similar to Hashemi even few days earlier, short plant height of 87 ± 3 cm, a greater 1000 grain weight of 31 ± 1.1 gr, an average grain yield of 7500 ± 500 Kg.ha-1, high tolerance against stripe stem-borer through antixenosis and antibiosis mechanisms, resistant to blast pathogen isolates with 0~1 infection type, good cooking quality with amylose content of 23 ± 1% and good aroma. Hence, with such a valuable characteristics, it has high potential for cultivating in irrigated system, as well as systems with water shortage, short growing duration, mechanized harvesting, double rice cropping and ratooning.

Solar radiation affects crop growth and development. Dry matter production by crops has often a positive relationship with radiation absorption by canopy and radiation use efficiency. Therefore, to evaluate radiation use efficiency of rice cultivars, a field experiment was carried out as split-split-plot arrangements in randomized complete block design with three replications in pilot plots in Qaleh-Tal district of Khuzestan province, Iran, in 2019-2020 and 2020-2021 growing seasons. Three rice cultivars; Champa, Anbouri and Danial were assigned to main plots, three planting arrangement; 15 cm × 15 cm, 15 cm × 20 cm and 15 cm× 30 cm, were randomized in sub-plots and seedling age at three levels; 30, 40 and 50-day old seedlings, in sub-sub-plots . Results showed that highest grain yield (9466 kg.ha-1) was recorded for cv. Danial in the 15 cm× 15 cm planting arrangement of 30-day seedling age treatment. The highest leaf area index (5.8) was achieved for cv. Champa in 30-day seedling age treatment. The highest crop growth rate (33.3 g.m-2 .day-1) observed for cv. Danial in 15 cm × 15 cm planting arrangement and 30-day seedling age treatment. The highest (1.95) and lowest (1.22 g,MJ-1) radiation use efficiency (RUE) were obtaibed in 30 and 50-day old seedlings, respectively. The increase of seedling age from 30 to 50 days led to incraese of light extinction coefficient from 0.06 to 0.10. The results of this experiment showed that 30-day old seedling at 15 cm × 15 cm planting arrangement treatment is more suitable for improving grain yield of rice cultivars in the target areas considering the low light extinction coefficient and high radiation use efficiency.