فصلنامه تحقیقات غلات
سال سیزدهم شماره 1 (بهار 1402)

Wheat ranks second among cereals in term of global production, but it has been affected by ongoing global climate changes. Drought stress is one of the important factors contributing to the reduction in wheat production. Developing drought-tolerant wheat varieties currently presents a major challenge for wheat breeders. Complex multigenic and multitrait genetic control, high genotype-environment interaction, low heritability, and challenges associated with high-throughput screening of plant traits and genes effective in drought tolerance due to the involvement of numerous traits and positive and negative correlations among them are some of the factors that have made wheat variety improvement for drought tolerance a challenging task. Selecting drought-tolerant genotypes as a cost-effective and biologically superior approach to increasing wheat production in low humidity areas has always been considered by breeders. Screening wheat genotypes to identify drought tolerance sources is essential and can be useful in selecting appropriate and desirable parents for implementing beneficial breeding programs. Local plant populations such as landraces are valuable resources for environmental stress tolerance, including drought stress. Local plant varieties are heterogeneous populations with local adaptation that provide genetic resources capable of meeting the needs imposed by new and emerging agricultural challenges under highly stressful conditions. The aim of this study was to identify wheat accessions tolerant to drought stress for use in future breeding programs.

A total of 512 wheat accessions from the National Plant Gene Bank of Iran, along with the varieties Kavir, Roshan and Mahouti as controls, were evaluated for drought stress tolerance in the research field of Agricultural and Natural Resources Research Center of Yazd, Iran. The experiment was conducted in two separate augmented designs, one of which was considered to drought stress and the other to normal irrigation conditions. Drought stress was induced by limiting the irrigation cycle. Considering that out of the total studied genetic materials, 141 accessions survived, the evaluation of traits was perfoemed on both those surviving accessions and their corresponding counterparts in the normal experiment. For data analysis, descriptive statistics including minimum, maximum, average, and coefficient of variation were calculated. Correlation coefficients were estimated and tested to study the relationship between traits. Stepwise regression analysis was used to determine the role of each trait and to identify the important and influencing traits on five-spike grain weight. K-means cluster analysis method was used to separate the accessions. All statistical analyzes were performed using R and SPSS softwares.

The results of descriptive statistics showed that the highest coefficient of variation under normal and drought stress conditions were attributed to five-spike grain weight (23.35%) and number of fertile tillers per plant (31.67%), respectively. Five-spike grain weight had the highest decrease in range (51.3%) under drought stress compared to normal conditions, and the highest decrease in mean was observed for number of fertile tillers per plant (59.3%) and five-spike grain weight (40.5%), respectively. A large number of accessions showed superiority over control varieties under both normal and drought stress conditions, so that 97 accessions had five-spike grain weight more than the control varieties. The accessions KC12856, KC12776, KC12783, KC12767, and KC12697 with values of 6.77, 6.75, 6.22, 5.94 and 5.86 g, respectively, had the highest five-spike grain weight under drought stress conditions. Number of spikelets per spike, number of florets per spikelet, 100-grain weight and number of grains per spike had significant and strong correlation coefficients at 1% probability level with five-spike grain weight under drought stress conditions. Based on the results of stepwise regression analysis under drought stress conditions, three traits including number of grains per spike, 100-grain weight and spike length were the most effective traits on five-spike grain weight and explained 90.6% of it’s variation. The studied genetic materials were grouped into five separated clusters using K-means cluster analysis.

The results of this experiment showed the valuable potential of the studied germplasm to drought stress tolerance. Evaluating the relationships among traits revealed the significance of number of grains per spikelet, number of spikelets per spike, number of florets per spikelet, and 100-grain weight under both normal and drought stress conditions. A considerable number of accessions were superior to the control varieties under both normal and drought stress conditions, indicating the richness and valuable potential of these genetic resources for drought tolerance related traits. Therefore, it is recommended to continue screening and evaluating the wheat collection of National Plant Gene Bank of Iran to identify drought stress-tolerant genetic resources. Based on the results of cluster analysis, the control cultivars with different characteristics were grouped in the separate clusters, and a distinguished cluster of the studied wheat accessions with superior traits was also formed. The diverse germplasm or superior accessions identified in this study can be used to develope the genetic base in crosses or as parents in breeding programs.

One of the effective strategies to control wheat diseases is to use a mixture of varieties. Basically, varieties with good and similar agricultural traits, but different in diseases resistance should be used. It is common to use a mixture of cultivars, when the high-yielding cultivar is sensitive and the low-yielding cultivar is resistant, so that their mixture has an acceptable efficiency. The mixture of cultivars is defined as a mixture of different cultivars that are similar enough to grow together, but differ in many traits such as disease resistance. The mixture of cultivars does not completely stop the disease, instead it reduces the disease progression rate by eliminating a large number of pathogen spores in each reproductive cycle. The aim of this research was to investigate the effect of mixed cultivation of three cultivars, Kohdasht, Moghan and Morvarid, in controlling four diseases, powdery mildew, tan spot, stripe rust and leaf rust.

To investigate the effect of the mixture of cultivars in control of wheat leaf diseases, a research was performed in a randomized complete block design with 12 treatments and four replications in the Gorgan Agricultural Research Station, Gorgan, Iran. The studied cultivars included three cultivars, Kohdasht, Moghan, and Maorvarid, and the evaluated diseases were four leaf diseases including powdery mildew, tan spot, stripe (yallow) rust, and leaf (brown) rust. Powdery mildew and tan spot were measured based on contamination rate using the Sari and Prescott scale, and atripe and leaf rusts were measured based on the disease type and severity. Final disease severity and standardized area under disease progression curve (SAUDPC) were evaluated for all four diseases.

The results of the statistical analysis of data revealed that there was a very significant statistical difference (P<0.01) between experimental treatments for the final disease severity and SAUDPC of all four diseases. The results of comparison of means for powdery mildew showed that all treatments had a final disease severity higher than 30% and lower than 45%. Therefore, none of the treatments could reduce the severity of this disease. However, in term of stripe rust, the resistance of Kohdasht and Morvarid cultivars and their mixtures was clearly observed. For tan spot, the lowest final severity of disease was recorded in Morvarid and 1:1 mixture of Kohdasht-Moghan, and the other mixtures of Kohdasht-Moghan could not significantly reduce the severity of this disease. In term of leaf rust, the lowest final severity of the disease was observed in Morvarid and Moghan cultivars with a density of 150 seeds per m2, and the highest final severity in Kohdast cultivar.

In this research, the effect of the mixture of cultivars in the control of wheat leaf diseases was investigated. In the case of powdery mildew, all treatments had a final severity of the disease higher than 30% and lower than 45%, and therefore, there is no proper efficiency in any of the treatments to reduce the severity of this disease. For yellow rust disease, the resistance of Kohdasht (treatment No. 1) and Marwarid (treatment No. 3) cultivars and their seed mixture (treatment No. 10) was clearly observed. In term of tan spot disease, the lowest final severity of the disease was observed in two treatments, Morvarid cultivar (treatment No. 3) and 1:1 mixture of Kohdasht and Mughan cultivars treatment No. 4), and the other proportions of the seed mixture of Kohdasht and Moghan varieties could not properly control the disease. In the case of brown rust disease, the lowest final intensity of the disease was observed in two treatments, Morvarid (treatment No. 3) and Moghan (treatment No. 12) with a density of 150 seeds per m2, and the highest severity of this disease was observed in the treatments belonging to Kohdasht variety.

Wheat is considered as a strategic plant in many countries including Iran. This crop has a special role in feeding and supplying energy to many people in world. In addition to economic aspects, the production of this crop is very important in term of food security. Due to the increase in global population and limited resources, serious efforts are being made to optimize agricultural processes and improve their productivity. In this regard, cultivation on high permanent ridges, known as “raised bed” planting, has been proposed as a new and efficient method in the production of various plants such as wheat. In many regions of the world including Iran, water is the most important limitation in agricultural productions. Raised bed cultivation method can improve water use efficiency. Therefore, in addition to the role of this method in improving yield per unit area, it is possible to produce more product with the available water resources. Also, in this method, preparation of seedbed and deep tillage is only needed in the first year to create ridges, and therefore energy consumption is also reduced in the following years. Regarding the effects of raised bed planting method, several studies have been conducted on different crops in some regions of the world, but due to the lack of consensus among these researches and the low generalizability of the results in the field of agriculture, it is necessary to conduct separate studies for each region and each crop. creates the need to conduct a separate study for each region and product. In the present study, the effect of raised bed planter in comparison with conventional grain drills was investigated on the quality of planting, water consumption, yield, costs, and economic profit of irrigated wheat cultivation.

To investigate the performance of different planters in a rotation system based on irrigated wheat, an experiment was carried out in a randomized complete block design with three treatments and four replications in Moghan agro-industry, Pars Abad county, Ardabil province, Iran, in 2021-2022 crop year. The treatments included planting with raised bed planter (four rows on a 75 cm width ridge), a typical grain drill (three rows on a 60 cm width ridge), and a grain drill without furrower (seeding + furrowing). The measured traits included field capacity, seed breakage rate, germination percentage, seed distribution uniformity coefficient (horizontal and vertical), water use efficiency, number of spikes per unit area, number of seeds per spike, grain yield and harvest index. Partial budgeting method and final rate of return were used for economic evaluation, and comparison of means were done by LSD test. Excel and SPSS softwares were used for economic and statistical analysis.

The results showed that raised bed planting had a significant effect on most of the yield components at 5% probability level, and on harvest index and grain yield at 1% probability level. The highest grain yield (8611.75 kg.ha-1) was obtained using raised bed planter, which was 7% and 8% more than the second and third planting methods, respectively. The harvest index for these three methods was 47.54%, 42.62% and 41.26%, respectively. The results of the economic analysis showed that the application of raised bed planter was the most profitable. The net profit from these three cultivation methods was 87.85, 51.91 and 42.51 million rials per hectare, respectively. The final return rate of replacement of the raised bed planter compared to the conventional seed drill and the seed drill without furrower was also calculated 123.95% and 173.73%, respectively.

The use of raised bed planter resulted in a significant increase in net profit in the first year, but multi-year studies are needed for a more comprehensive investigation. The need for deeper tillage and the preparation of high ridges in the first year, as well as the high price and low field capacity of the planter, increased the costs of the seedbed preparation and planting operations, but the reduction in seed consumption to some extent moderates this increase in cost. In contrast, the increase in revenue resulting from a significant increase in crop yield was much greater than the cost changes. In addition to increasing the direct profit of farmers, saving water and energy in the raised bed cultivation method is another reason for the preference of this method over the conventional methods, because farmers do not pay the real cost of these two inputs. However, more studies are needed to remove the obstacles to the expansion of this cultivation method.

The first step in breeding programs is to use the genetic diversity among existing populations, cultivars and lines. Maize is used as a model plant to study the genetics of various traits. Compared to other crops, maize has a high demand for zinc (Zn) and is known as an indicator of zinc deficiency in the soil. In terms of climatic conditions, Iran is located in a arid and semi-arid region, and there is a lack of micronutrients specially Zn in this region. Lack of nutrients such as Zn is one of the important abiotic stresses that affects the growth and development of plants including maize. The objective of this study was to evaluate the genetic diversity of a number of corn lines under normal and zinc deficiency conditions.

To assess the genetic diversity of 95 maize lines using agro-morphological traits, an experiment was carried out in alpha lattice design in two replications under two normal (use of zinc sulfate fertilizer) and zinc deficiency (no use of zinc sulfate fertilizer) conditions in Zabol Agricultural Research Center during two years. The studied maize lines were obtained from Razi University of Kermanshah, Khorasan Razavi Agricultural and Natural Resources Research Center, and Seed and Plant Improvement Institute (SPII) in the form of research project No. 94/101/T.T. approved by Biotechnology Institute of Urmia University. Twenty-nine traits were measured and recorded. Combined analysis of variance of the studied traits under normal and zinc (Zn) deficiency conditions were performed using SAS ver. 9.4 software. Other statistical analyzes including descriptive statistics, Pearson correlation coefficient, forward stepwise regression and factor analysis method were done using R software by pastecs, corrplot, olsrr, and psych packages, respectively.

The results of this study revealed high phenotypic variation among the studied maize lines for all investigated traits under both normal and zinc (Zn) deficiency stress conditions. The results of analysis of variance confirmed the presence of high phenotypic diversity among maize lines. All traits were affected by environment, and a statistically significant difference was observed between two environments for the all measured traits in maize lines. Genotype × environment interaction was also significant for most of the studied traits. Descriptive statistics showed a considerable diversity among the lines, and the highest diversity in both normal and zinc deficiency conditions was observed for yield per unit area, economic yield, and number of grains per cob. In correlation analysis, weight of five cobs, number of grains per cob, and 100-grain weight showed a positive and significant correlation with economic yield in both normal and zinc deficiency conditions. Therefore, these three can be introduced as important traits in the initial selection of zinc deficiency tolerant lines. In factor analysis of morphological traits using the parallel analysis method, four hidden and independent factors were determined under both normal and zinc deficiency conditions, which explained 63% and 57% of the total variation of the lines, respectively. Based on the results of the factor analysis, the traits number of days to tasseling, number of days to pollen emergence, number of days to cob emergence, plant height, ear diameter and width, number of grains per cob, economic yield, yield per unit area, and harvest index with high degree of commonality under both normal and zinc deficiency conditions, can be suggested as key traits for the selection of zinc deficiency tolerant lines.

The results of this research showed that there is a high genetic diversity among the studied maize lines in terms of morphological traits under both normal and zinc deficiency stress conditions. It makes it possible to use these lines in breeding programs as a valuable genic source to improve the performance of lines and produce improved lines under normal and zinc deficiency conditions.

Salinity of soil and water resources are the most important factors reducing yield in many crop plants, including rice. Considering the increase in salinity of soil and water resources in many paddy farms in Iran, and considering the different sensitivity of rice plants at different growth stages to water and soil salinity, it is necessary to manage saline water resources in these areas. In this experiment, the effects of different levels of irrigation water salinity on grain yield of two hybrid (Bahar) and improved (Dorfak) rice varieties at different growth stages were investigated. The objective of this experiment was to obtain the best application time of saline water with the minimum reduction of rice grain yield.

This study was conducted as a pot experiment in factorial based on completely randomized design with three factors and three replications in the Rice Research Institute of Iran (RRII), Rasht, Iran. The experimental factors included irrigation water salinity in four levels as the first factor, 2, 4, 6, and 8 dS/m, application time of salinity stress in four levels as the second factor, tillering, panicle formation, heading and maturity growth stages, and rice variety in two levels as the third factor, the hybrid variety of Bahar and the improved variety of Dorfak. Moreover, irrigation with normal water with a salinity of 0.4 dS/m was also considered as a control treatment for comparison with the other salinity treatments. A mix of NaCl+CaCl2 salts in a ratio of 2:1 were used to apply salinity treatments. After the end of each growth stage, leaching was carried out and irrigation with normal water was continued until the end of the growth stage. At the end of the growth and harvesting grains, grain yield based on 14% moisture, biological yield and harvest index were measured. SPSS software was used for statistical analysis and Tukey's test was used to comparison of means at 1% probability level.

The results of analysis of variance indicated that the effect of different salinity levels and its application stage on grain yield of both rice varieties was significant at 1% probability level. The results of comparison of means revealed that the improved variety Doefak showed more salinity tolerance and produced more grain yield at different salinity levels compared to the hybrid variety Bahar. The most sensitive and resistant growth stages to salinity stress were tillering (with an average grain yield of 6.82 g/pot for the hybrid variety Bahar and 8.07 g/pot for the improved variety Dorfak) and maturity (with an average grain yield of 14.71 g/pot for the hybrid variety Bahar and 15.90 g/pot for the improved variety Dorfak) stages, respectively. The lowest biological yield (14.37 g/pot) and harvest index (2.53%) in the improved variety Dorfak was obtained at the tillering stage and the salinity level of 8 dS/m. Also, the lowest biological yield (12.89 g/pot) and harvest index (4.61) in the hybrid variety Bahar was observed at the salinity level of 8 dS/m and at the heading and panicle formation stages, respectively. Modeling the effect of different salinity levels on grain yield indicated that yield variations in different salinity levels and at the different growth stages followed a quadratic equation. Coefficients of determination of the regression equations of grain yield in different salinity levels for the improved variety Dorfak at the tillering (R2=0.99), panicle formation (R2=0.99), heading (R2=0.95) and maturity (R2=0.98) stages, and also for the hybrid variety Bahar at the tillering (R2=0.99), panicle formation (R2=0.99), heading (R2=0.99) and maturity (R2=0.99) stages, revealed that the application time of salinity stress is more important than the salinity levels.

Application of different salinity levels caused a significant difference in grain yield of both improved and hybrid varieties, so that a significant decrease was observed in grain yield of both Dorfak and Bahar varieties with the increasing salinity levels, and the lowest grain yield was obtained at the salinity level of 8 dS/m. Application time of salinity stress was also very important and caused a significant difference in reduction of grain yield. The results of this experiment showed that under the water limitation conditions or in the absence of suitable water quality, it is possible to prevent the reduction of rice grain yield by managing irrigation water at different growth stages and using lower quality water in the final and maturity growth stages.

The increasing demand for diverse fodder plants, along with the challenges of its production such as the pressure on pastures, has led to increased attention to strategies for maximizing the production of these plants per unit area. Millets are a good choice for crop rotation and production patterns in different regions due to their high diversity, high adaptability, high dry matter production, and high nutritional value. However, the appropriate planting date and the compatibility of the growth stages of millet with environmental conditions are essential for maximizing production. This study was conducted to evaluate the effect of different planting dates on the growth indicators of proso millet and how its growth stages are compatible with environmental conditions.

To achieve the objectives of the research, a two-year field experiment was conducted in 2016-2017 and 2017-2018 at the research farm of the Faculty of Agricultural Sciences of the University of Guilan. A randomized complete block design with four replications and four planting dates was used (May 29, June 27, July 29, and August 29 in the first year; and June 4, July 7, August 5, and September 6 in the second year). Plant growth indices, plant response, and the compatibility of plant growth stages with environmental conditions were investigated through repeated sampling, measurement of plant leaf area and dry matter of different plant parts, and recording of phenological stages.

The results of this experiment showed that the interaction between year, planting date, and sampling time had a significant effect on the accumulation of dry matter and the growth indicators studied, such as leaf area index (LAI), crop growth rate (CGR), relative growth rate (RGR), net absorption rate (NAR), leaf area ratio (LAR), and leaf weight ratio (LWR). In the first cropping year, the highest total dry matter accumulation of proso millet, with an average of 1030.8 grams per square meter, was obtained by planting it on June 27. This was due to the maximum LAI (5.14 cm²·m²) and crop growth rate (35.5 g·m²·day⁻¹) obtained in the second planting time, which led to a significant increase in dry matter compared to the other three planting dates. However, in the second year of the experiment, planting proso millet on June 4 resulted in a significant increase in LAI (3.69 cm²·m²), CGR (25.99 g·m²·day⁻¹), and NAR (18.13 g per square meter of leaf area per day) compared to the other three planting dates. As a result of the aforementioned growth indicators, the total dry matter accumulation of proso millet was 734.66 grams per square meter, which showed a significant increase compared to the other three planting dates.

Overall, the results of this experiment suggest that the optimal planting date for proso millet in Rasht is between June 4 and June 27. Planting during this period resulted in the highest accumulation of dry matter and the most favorable growth indices. The findings of this study can be used to improve the cultivation practices of proso millet in Rasht and other similar regions.