فصلنامه تحقیقات غلات
سال دوازدهم شماره 3 (پاییز 1401)

Rice is a valuable and strategic cereal that plays an important role in providing food security for more than 50% of the world's population. New rice production systems require stable management operations. The role of nitrogen as a key determining factor is necessary to achieve optimal yield. As a synthtic growth regulator, mepiquat chloride is one of the important management tools in reducing stress damage and overcoming many agricultural problems, such as lodging. Mepiquat chloride reduces the distance between nodes in the main stem and tillers. The objective of this experiment was to investigate the effect of nitrogen fertilizer and mepiquat chloride on yield, yield components and lodging resistance indicators in rice.

To investigate the effect of nitrogen fertilizer rates and the foliar application of the growth retardant mepiquat chloride on lodging resistance and grain yield of rice cv. Hashemi, a factorial experiment based on a randomized complete block design with three replications was carried out during the spring of 2020 in the experimental field of Agriculture and Natural Resources Research Center in the village of Keshel Varzal in Rasht County, Guilan province, Iran. The experimental treatments included mepiquat chloride at four levels (no foliar application, and foliar application at the maximum tillering stage, stem elongation stage, and maximum tillering + stem elongation stages) and  nitrogen (N) fertilizer at three levels (13 kg.ha-1, 32.5 kg.ha-1, and 52 kg.ha-1). The studied traits also included the morphological characteristics (bending moment of internodes) related to the third and fourth internodes lodging, breaking resistance at the middle point of third and fourth internodes and lodging index, grain yield, number of panicles per plant, total number of grains per panicle, number of filled and unfilled grains per panicle and 1000-grain weight.
Research

The results showed that the highest grain yield (3999 kg.ha-1) was obtained from the foliar application of mepiquat chloride at the maximum tillering stage along with the application of 52 kg.ha-1 N and the lowest (2169.6 kg.ha-1) from no foliar application along with the application of 13 kg.ha-1 N. The maximum number of panicles per plant, number of total grains and filled grains per panicle were recorded in the mepiquat chloride foliar treatment at the maximum tillering stage and the application of 52 kg.ha-1 N. The lowest number of panicles per plant (and the number of filled grains per panicle) was obtained in the treatment of mepiquat chloride foliar application in the treatment of stem elongation and application of 13 kg.ha-1 N. The highest bending momentum of the third and fourth internodes (1563 and 1663.9 g.cm-1, respectively) was related to the foliar application of mepiquat chloride at the maximum tillering stage. Among the N fertilizer levels, the highest bending momentum of the third and fourth internodes (1521.1 and 1581.6 g.cm-1, respectively) were obtained from the application of 32.5 kg.ha-1 nitrogen.

Application of growth regulators and optimal use of nitrogen fertilizer are ways to prevent decline in rice grain yield. Foliar application of plant growth regulators and nitrogen chemical fertilizer on the plant characteristics of rice can help to improve resistance to plant lodging. According to the results of this experiment, it seems that foliar application of mepiquat chloride at the stage of maximum tillering and consumption of 52 kg.ha-1 nitrogen is the most suitable treatment for Hashemi rice cultivar in terms of increasing grain yield and resistance to plant lodging in climatic conditions of Rasht.

IntroductionWheat is one of the most stable crop in the world, and drought stress is one of the major environmental factors that reduce agricultural products. Evaluation of genetic diversity in plant breeding program is the main basis for development and achieving self-sufficiency in the agricultural product. The objective of this experiment was to investigate the association between microsatellite markers and genomic regions controlling yield, physiological, and phenological traits in 23 accessions and two cultivars of bread wheat, as well as to evaluate the genetic diversity of the studied population in term of yield, physiological and phenological traits, and microsatellite markers under rainfed and irrigation conditions.Materials and methodsA field experiment was carried out in a randomized complete block design with three replications under rainfed and irrigation conditions in the research field of Razi University, Kermanshah, Iran, in 2016-2017. Grain yield, 15 physiological traits and six phenological traits were measured. Twenty microsatellite markers were used for molecular evaluation of the studied genotypes. Genomic DNA was extracted as bulk from 2-3 weeks old seedlings by modified CTAB method. To determine the quality and quantity of the extracted DNA, electrophoresis on 0.8% agarose gel was used. Finally, the association between microsatellite markers, yield, physiological and phenological traits in rainfed and irrigated conditions was calculated using stepwise regression analysis by SPSS23 software.Research findingsAnalysis of variance showed that there was a significant difference between the accessions for most of the traits studied. Sixteen out of twenty markers had detectable polymorphisms. The XCFD168-2D, XGWM350-7D and XGWM136-1A primers were the most suitable primers for subsequent studies. Association analysis by stepwise regression showed that in rainfed and irrigation conditions, markers XGWM350 (a3) and XGWM334 (a1) were common for physiological traits and markers XGWM642 (a1), XGWM350 (a1), and XCFD168 (a1) were common for phenological traits. The XGWM410 (a1) marker on yield, physiological and phenological traits in both conditions; XGWM265 (a1) marker on yield and physiological traits in irrigation conditions and phenological traits in both conditions; XGWM124 (a2) marker on yield and some physiological traits in rainfed conditions and phenological traits in both conditions; XGWM165 (a1) marker on physiological and phenological traits in rainfed conditions, and XGWM577 (a2) markers on grain yield and physiological traits in irrigation conditions and some phenological traits in rainfed conditions were jointly related. In addition, the most positive markers in rainfed conditions are related to the trait of rate of filing seed, and in irrigated conditions, respectively, they are related to grain yield, water use efficiency, rate of filing seed, relative water content, and days to physiological maturity traits.ConclusionAccording to the evaluation of the genetic diversity of primers XCFD168-2D, XGWM350-7D and XGWM136-1A, the most suitable primers for wheat were introduced in subsequent studies. Based on the association analysis, most of the markers produced by the primers used in this research had a high significant associated with the studied traits, and by using these primers, which have the ability to reproduce informative loci, plants can be screened at the seedling stage. Furthermore, The microsatellite primers linked to traits are suggested in marker assisted selection breeding programs to identify suitable parents for constructing mapping populations and producing new varieties.

IntroductionDurum wheat (Triticum turgidum L. var. durum) or hard wheat, is the second most important wheat crop species. Since durum wheat is mainly cultivated under dryland conditions in the Mediterranean region, its yield is strongly affected by abiotic stresses, especially drought and salinity. Salinity stress causes osmotic stress and disrupts the ionic balance of the cells and plant physiologic processes such as seed germination and seedling growth. This study was conducted to identify durum wheat salinity tolerant genotypes at germination stage using multi-trait selection indices such as multi-trait genotype-ideotype distance index (MGIDI) and the ideal genotype selection index (IGSI). Materials and methodsThe plant materials of this research were 50 different durum wheat genotypes, which were evaluated for salinity tolerance at germination stage. The experiment was conducted as a factorial in a completely randomized design with three replications. To create salinity stress, sodium chloride (NaCl) was used at three levels including 0 (control), 150 mM (~15 dS.m-1), and 300 mM (~30 dS.m-1) concentrations. To evaluate the salinity tolerance of the studied genotypes, quantitative stress tolerance indices were first calculated based on root (radicle) and shoot (plumule) dry weight under non-stress conditions (Yp) and average salinity levels (Ys) for each genotype. Then according to the results of factor analysis based on principal component analysis (PCA), the MGIDI index was calculated using the factor scores of the first two factors with eigen values greater than one. The IGSI index for each genotype was also calculated using all stress tolerance indices. Research findingsThe results of factor analysis based on principal component analysis (PCA) showed that the first two factors with eigen values greater than one explained 99.6 of the total variance. The calculation of the MGIDI index based on the factor scores of the studied genotypes showed that in average salinity stress conditions, genotypes 6, 23, 5, 30, 34, 29, 31, 2, 10, 39, 13, 9, 47, 12, 52, 48, and 1 with lower values of MGIDI (between 0.90 and 2.50) and higher values of IGSI (between 0.65 and 0.80) were the best genotypes in term of salinity tolerance. In contrast, genotypes 46, 43, 19, 26, 4, 15, 42, 38,11, and 37 with the lower values of IGSI and the higher values of MGIDI, were considered as weak and sensitive genotypes to salinity. The coefficient of determination (R2) between these two indices for all genotypes was 92%, indicating a high correlation between these two indices and the selection of same genotypes. ConclusionThe results of the present study showed that there was a significant genetic diversity among the studied durum wheat genotypes for salinity tolerance at the germination stage, which can be used in the breeding programs of this valuable crop. IGSI and MGIDI indices were also effective in identifying superior genotypes based on all stress tolerance indices. Therefore, these indices can be recommended to select salinity tolerant genotypes based on different traits in breeding programs.

IntroductionMaize is one of the most important sources of energy supply to feed poultry, livestock, as well as humans, and the primary and raw material for industrial and food products. This valuable crop plant in terms of world production ranks third after wheat and rice. Since knowing the genetic diversity in germplasm collections and determining the genetic relationships between breeding materials is the first and most important step in breeding researches, so identifying high diversity and suitable genetic potential lines is one of the goals of plant breeders to product and introduce new varieties. The objective of this study is to investigate the genetic diversity of 18 maize inbred lines using microsatellite (SSR) markers, to evaluate the efficiency of the studied markers, and to introduce the most appropriate ones in determining the genetic diversity of maize lines.Materials and methodsThe plant materials of this research included 18 inbred lines of maize prepared from the Agriculture and Natural Resources Research Center of Khorasan-Razavi province, Iran. DNA extraction was carried out by CTAB method from fresh and young leaf samples after the three-leaf stage of seedlings. Polymerase chain reaction (PCR) was performed in a final volume of 10 μl, and horizontal electrophoresis on 3% agarose gels as well as vertical electrophoresis on 6% polyacrylamide gels were used to observe the amplified fragments. For data analysis, first the amplified fragments (bands) on the gels were valued and quantified, so that the numbers 1 and 0 were considered for the presence and absence of each band in each maize line, respectively. To evaluate the genetic diversity, different diversity indices including number of effective alleles, polymorphic information content (PIC) and Nei’s gene diversity were estimated using POPGEN software, and the most suitable markers were introduced. To group the studied maize lines, cluster analysis and principal coordinates analysis were performed and the corresponding graphs were drawn using NTSYSpc 2.0 software.Research findingsAssessing the genetic diversity of maize lines based on microsatellite markers showed that 20 SSR markers used in this research amplified a total of 81 scorable loci, whose size ranged from 65 to 200 bp. The average number effective alleles, polymorphism information content and Nei’s gene diversity were calculated as 2.05, 0.71 and 0.62, respectively, indicating that there was a considerable genetic diversity among the studied maize lines. Evaluating the polymorphic information content (PIC) index showed that the markers used in this study had highly variable PIC from 0.28 (for Phi024) to 0.91 (for Phi038) with an average of 0.71. Cluster analysis by UPGMA method using Jaccard similarity coefficient grouped 18 maize inbred lines into three distinct clusters with 1, 6 and 11 lines, respectively. Molecular analysis of variance based on three groups derived from cluster analysis showed that 11% and 89% of the total variance was between and within population, respectively. The results of principal coordinate analysis and grouping if maize lines based on the bi-plot of the first and second vectors confirmed the grouping of the cluster analysis.ConclusionThe results of the current study showed that there was a significant genetic diversity among the studied maize lines, which can be used in breeding programs. Also, microsatellite markers (SSRs) had the ability to assess the genetic diversity and separation of maize genotypes from each other. Evaluating the different diversity indices for the studied markers in this research showed that the markers Phi034, Phi038, Phi076, Phi084, and Phi092 were more suitable markers for determining genetic diversity. Therefore, it is recommended to use these informative markers to determine genetic diversity as well as to identify heterotic pattern in maize breeding programs.

IntroductionThe seed is the most important input of the agricultural section, which provides the reproduction, survival and extension of the plant. Therefore, identifying the factors affecting seed production and its quality at the production and harvesting stages is very important. Previous reports show that the use of soil modifier compounds such as biochar, arbuscular mycorrhizal fungus (AMF), and silicon foliar application can improve the germination indices of produced seeds under environmental stressess conditions, especially salinity stress. So far, the experiments conducted to investigate the effect of biochar, mycorrhizal fungus and silicon foliar application on plant growth and salinity stress tolerance have mostly been about the individual applications of each of these soil modifiers, and there is little evidence of their synergistic effects, especially for plants grown under saline soil conditions. The objective of this experiment was to investigate the synergistic effects of biochar, arbuscular mycorrhizal fungus and silicon foliar application on improving the quality of mother class seeds of maize variety under saline soil conditions. Materials and methodsThis study was conducted as a factorial experiment in a randomized complete block design with three replications in a research field with an electrical conductivity of 6.01 dS.m-1, in Fasa city, Fars province, in 2020. The first factor was three varieties of maize, including early- maturity variety 370, mid-maturity variety 604, and late-maturity variety 704, and the second factor was soil modifier compounds in eight levels, including no-application of modifier compounds as control, biochar, AMF, silicon foliar application, biochar + AMF, biochar + silicon, AMF + silicon and biochar + AMF + silicon. The measured traits included the concentration of sodium and potassium, activity of alpha and beta amylase enzymes, and seed germination and seedling growth indices. Statistical analyzes including analysis of variance and comparison of means were performed with Duncan's multiple range test at the 5% probability level using SAS software ver. 9.1. Research findingsThe results of this experiment showed that sodium concentration of seedling in cultivar 704 was reduced by 31% in the combined treatment of biochar + mycorrhizal fungus + silicon foliar application compared to the control treatment. The use of soil modifier treatments alone and in combination caused a decrease in the ratio of sodium to potassium, electrical conductivity of seeds as well as an increase in potassium concentration. An increase of 57% and 25% of alpha and beta amylase enzymes was observed in the combined treatment of biochar + mycorrhizal fungus + silicon foliar application compared to the control treatment. Also, application of soil modifier resources alone at a lower level could cause a significant increase in germination percentage. Seedling dry weight in the combined treatment of biochar + mycorrhizal fungus + silicon foliar application showed an increase of 15% and 10% in varieties 604 and 370, respectively. On the other hand, the highest seed germination and 1000-grain weight in the studied corn varieties were also observed in the combined treatments of biochar + mycorrhizal fungus + silicon foliar application. ConclusionIn total, the results of this experiment showed the positive effect of soil modifier sources in improving of germination characteristics and seedling growth indices of corn varieties. Based on these results, the combined application of biochar + mycorrhizal fungus + silicon foliar application is recommended to improve the quality of seed production in corn varieties under salt stress conditions.

IntroductionTarget leaf spot of sorghum, caused by fungal species Bipolaris sorghicola, is considered as one of the most important leaf diseases in sorghum, so that occurrence before flowering, can lead to damage and reduction of more than 50% of grain yield. This disease is also significant in Iran and usually occurs in most of the humid regions of the country, where sorghum is cultivated. Since there are very few researches on leaf spot diseases in sorghum especially on the resistance of sorghum cultivars in the country, it seems necessary to carry out research in this field. Therefore, the present research was carried out with the aim of evaluating the response of different sorghum genotypes to leaf spot disease. The resistant genotypes identified in this research can be used to transfer favorable characteristics to the host plant in future breeding programs.Materials and methodsTo study the reaction of different forage sorghum genotypes to target leaf spot, 25 sorghum genotypes, including ten commercial hybrids and 15 promising lines were evaluated in a randomized complete block design with three replications in two regions, Karaj and Gorgan. Artificial inoculation of genotypes in the field was carried out with a mixture of several pathogenic isolates of the disease-causing fungus in two stages. The first, at the 3-4 leaf stage by injection of spore suspension (3 ml per each whorl) using a syringe stage, and the second, at the 6-8 leaf stage using the Bazooka method by placing 2-3 fungus infested sorghum grains in the whorl of each plant. To evaluate the reaction of genotypes and progress of the disease, characteristics such as percentage of disease incidence (DI%) and disease severity on each plant (DS%) were recorded two weeks after the last inoculation. In addition to the field experiment, the reaction of the genotypes to the disease was investigated in a greenhouse experiment based on a completely randomized design with three replications.Research findingsThe results of this experiment showed that there was a significant difference between the studied sorghum genotypes in terms of resistance or susceptibility to leaf spot. Comparison of genotypes showed that the disease severity of the studied lines and hybrids varied from 0.7% to 51.7% in the Karaj region, and from 1.7% to 66.3% in the Gorgan region. Hybrid No. 8 (FGCS110) with 0.7% and 1.7% disease severity in the Karaj and Gorgan regions, respectively, had the lowest disease severity and was recognized as the most resistant genotype in both regions. In contrast, line No. 2 (FGS109) with disease severity of 51.7% and 66.3% in Karaj and Gorgan regions, respectively, was the most susceptible genotype. Furthermore, a statistically significant difference was observed among the studied regions for disease severity of all genotypes, so that the recorded disease severity in Gorgan was higher than in Karaj. Also, there was a positive and significant correlation (r = +0.74, p< 0.01) between disease severity (DS%) and disease incidence (DI%) measured in different sorghum genotypes in two studied locations. The results of greenhouse experiment also confirmed the results of field experiment.ConclusionThe results of the current research led to the identification of resistant and semi-resistant sorghum genotypes to leaf spot among the studied genetic materials, which can be used in future breeding programs. The results obtained from the Karaj region showed that genotype No. 8 (foreign hybrid FGCS110) was highly resistant, line No. 13 and foreign hybrids No. 1, 6, 7, and 10 were resistant, and the number of 11 lines along with a foreign hybrid were semi-resistant. In the Gorgan region, foreign hybrids No. 7, 8, and 10 were resistant, and seven lines and five foreign hybrids also had a semi-resistant reaction to the disease, while no resistance reaction was observed in any of the studied lines in this region.