فصلنامه علوم زراعی ایران
سال بیست و پنجم شماره 2 (پیاپی 98، تابستان 1402)

The crisis of water sources limitation has signified the necessity of irrigation management of canola crop unavoidable. This issue is especially critical in the context of climate change, which is accompanied by changes in precipitation amount and patterns as well astemperature flucatations. The time-consuming and costly nature of field research and the spatial and temporal dependence of the results have caused crop growth modelling to be considered as an effective and acceptable technique in decision support systems under climate change conditions. In this regard, the DSSAT program is one of the most successful programs available for simulating the growth and development of crops. In this study simulation program for plant growth and development was used to predict growth and seed yield of canola in Dehgolan in Kurdistan province of Iran.

This study consisted of two phases; field and simulation studies. Statistical Downscaling Model (SDSM) was used to simulate climate data and forecast climate changes in the future. For the future climate, the set of CanESM scenarios including; RCP2.6, RCP4.5 and RCP8.5 scenarios, presented by the Canadian Earth System Modeling Center, were used. Then, the changes in the growth and yield of canola under the mentioned scenarios were studied in the four periods of 2021-2040, 2041-2060, 2061-2080, and 2081-2100 using the CSM-CROPGRO-Canola model in the DSSAT program. In field studies, two field experiments were carried out to calibrate and validate the output of the model in the research farm of the Kurdistan University in Dehgolan 2016-2017 and 2017-2018 cropping seasons.

The results of validation for weather and growth models showed that the models had sufficient accuracy to simulate climate variables and also the growth of canola. The simulation results illustrated that the growth characteristics of canola were affected by the negative effects of climate change under all scenarios and different time periods, therefore, the plant traits in various climate change scenarios were low when compared to the baseline cropping season (2018-2019). In general, the results of the model showed that the maximum negative effects of climate change on canola growth was in the RCP8.5 scenario and the minimum in the RCP2.6 scenario. The adverse effects of climate change were accelerated by time, especially in the RCP8.5 scenario.

The results of this study showed that the future climate change will have a negative effect on the growth and yield of canola that depends on the scenario and time period, the seed yield will decrease from 0.3% to 37.58% as compared with the current conditions. Therefore, to mitigate climate change impact on agricultural ecosystems necessary management measures including development of suitable canola cultivars and agronomic mangament package should be taken into consideration for adaptation to the changing climate in future.

Soybean seed contains about 20% oil and 40% protein and is considered as a strategic oilseed plant. Identification of the relationship between morphological traits and seed yield and improving the traits that have strong associtation with seed yield can increase the efficiency of the soybean breeding programs for seed yield improvement.

To determine the suitable indirect selection index for seed yield in soybean, the important morphological traits were evaluated in 10 soybean cultivars in randomized complete block design with three replications and multivariate statistical methods in research farm of Sari University of Agriculture Sciences and Natural Resources, Sari, Iran, in two growing seasons (2020 and 2021).

The results showed that there was significant differences between soybean cultivars for the morphological traits which indicates considerable variation among Iranian soybean cultivars. The results also showed that cv. Telar with the highest number of branches, number of pods plant-1, number of seeds pod-1 and pods weight plant-1 had the highest seed yield (5400 kg.ha-1) in the 2020 and cv. Katol with the tallest plant height, the highest number of branches, pods weight plant-1 and the 100-seed weight had the highest seed yield in 2020 and 2021 (5200 and 7688 kg.ha-1, respectively). The results of multivariate analysis showed that among the studied traits, pods weight plant-1 and plant height directly, the number of pods plant-1 with a direct effect on the pods weight plant-1 and also the 100 seed weight with a direct effect on plant height had highly positive effects on seed yield in soybean. Furthermore, the number of pods plant-1 showed negative relationship with 100 seed weight. Moreover, the results of cluster analysis showed that cv. Telar and cv. Parto were distinguished from other cultivars for short plant height and high number of pods plant-1, cv. Katol for tall plant height and high 100-seed weight and cv. Tapur for high number of seeds pod-1.

Since pods weight plant-1, plant height, number of pods plant-1 and 100 seed weight showed high positive direct effects on seed yield, therefore, cv. Prato and cv. Telar with the highest number of pods plant-1 and cv. Katol with the tallest plant height and the highest 100 seed weight can be considered for seed yield improvement in soybean breeding programs.

High plant density is considered as a stress that affects growth and developmental stages of crops throughout the life cycle. Results of previous studies have indicated that high yielding maize cultivars under high-density planting conditions are better adapted to most environmental stresses. Therefore, maize breeders use high plant density to identify cultivars tolerant to environmental stresses. The present study was conducted with the objective of evaluating 97 promising hybrids and parental lines of maize under high plant density planting conditions, facilitating the identification of cultivars tolerant to unfavorable environmental conditions.

This study consisted of four seperate experiments conducted on 21 early-maturity lines (first trial), 26 late-maturity lines (second trial), 24 early-maturity hybrids (third trial), and 26 late-maturity hybrids (fourth trial) of maize. The experiments were carried out in randomized complete block design with three replications at research field of Seed and Plant Improvement Institute, Karaj, Iran, in 2020 and 2021 growing seasons. The late- and early-maturity lines and hybrids were cultivated at plant densities of 140000 and 160000 plants.ha-1, respectively. Grain yield, number of grain rows ear-1, grain number row-1, 1000 grain weight, grain number plant-1 and test weight (hectoliter) were measured and recorded.

The results showed considerable variations in grain yield of maize hybrids and parental lines across different trials. In the first trial, line No. 12 with 8262 kg.ha-1 had the highest grain yield.  In the second trial, the highest grain yield (6025 kg.ha-1) obtained from line No. 12. In the third trial, hybrid No. 1 had the highest grain yield (9594 kg.ha-1), while in the fourth trial, hybrid No.10 with 8313 kg.ha-1 had the highest grain yield. Principal component analysis also indicated that the t suitable adapted genotypes for cultivation under high-density planting conditions included; early-maturity line KE781010/521, the late-maturity line K47/2-2-1-2-2-1-1-1, early-maturity hybrid K1263/17×MO17, and late-maturity hybrid K47/2-2-1-3-3-1-1-1×K166B.

Based on the results of all four experiments, which demonstrate significant and positive correlation between grain yield and grain number row-1, grain number plant-1, and ear number plant-1, it can be concluded that maize genotypes adapted to high plant density planting conditions produce more grains and ears in high plant density conditions are better adapted to environmental stresses.

The genotype and environment interaction is one of the main challenges in the breeding of different crop plants and causes different genotypes to perform differently under different environments. Assessment of genotypes and environment interaction for quantitative traits such as grain yield is very important for development of new improved cultivars.

Nineteen barley promising lines together with a commercial barley cultivar (cv. Behrokh as check) were evaluated across eight agricultural research stations in Karaj, Varamin, Neishabour, Mashhad, Birjand, Yazd, Isfahan and Shiraz (Zarghan) in 2020-21 and 2021-22 cropping seasons. Combined analysis of variance was performed for grain yield, andGGE bi-plot graphic analysis used fore the assessment of grain yield stability of barley promising lines.

The results of combined analysis of variance showed that the effects of location, genotype, year × location and genotype × year × location interaction effect were significant on grain yield. Mean comparison, using LSD test, showed that promising lines; No. 3, No. 4, No. 11, No. 12 and No. 13 with grain yield of 6673, 6663, 6412, 6340 and 6249 kg.ha-1, respectively, were high yielding compared with cv. Behrokh as well as others. The grain yield stability analysis facilitated to identify promising lines with with high grain yield and yield stability. In the first year lines; No. 3, No. 4 and No. 11, in the second year lines; No. 4 and No. 12 and in the two years lines; No. 3 and No. 4 were close to the ideal genotype.

Barley promising lines; No. 3 and No.4 were identified as high yielding with high yield stability. These promising lines are adapted to temperate agro-climatic condition in Iran and can be used in irrigated barley breeding programs. Of the eight test locations, Karaj was the most discriminative and representative environment. Therefore, this location can be recommended as a suitable test location for the selection of superior genotypes adapted temperate agro-climate conditions in Iran.

As one of the most important crops in Khuzestan, Iran, forage maize production faces limitations such as deficincy of water resources in summer, low soil organic matter content, heavy soil texture and soil salinity, which can be resolved by appropriated nutrition management and planting method to reduce some of these problems. To improve soil fertility, integrated application of chemical and organic fertilizers is eco-friendly and economically sustainable. The integarated application of organic and biological fertilizers in combiation with chemical fertilizers is an important integrated plant nutrition management strategy for sustainable productivity and production in cropping systems.

To evaluate the physiological traits and yield of silage maize with with integrated application of nitrogen fertilizer and sugarcane residue compost and seed sowing method under drought stress conditions, a field experiment was carried out in split split plot layout in randomized complete block design with three replications in 2021 summer in Ramhormoz, Khuzestan province, Iran. Treatments included irrigation after 30% (non-stress), 50% (moderate stress) and 70% (severe stress) deplation of available soil water (main plots), fertilizer treatments included 100% of nitrogen fertilizer requirement; 75% nitrogen + 25% compost, 50% nitrogen + 50% compost, 25% nitrogen + 75% compost and 100% compost (sub plots) and sowing methods, top of beds and in furrows (sub-sub plots). Samples of fresh forage were used to determine the relative water content (RWC), dry matter content and the dry forage yield. The leaf greenness index (SPAD) was measured using a portable chlorophyll meter at the 50% flowering stage on the fully developed leaf. Forage quality traits were measured using near infrared spectroscopy (NIR).

The results showed that the highest values of SPAD, chlorophyll a, chlorophyll b, RWC and cell membrane stability were obtained in 100% chemical fertilizer treatment under well irrigated condition. However, under modeate and severe drought stress conditions, combination of chemical and organic treatments with the 50% nitrogen and 50% compost of sugarcane residues had higher values. The maximum dry forage yield was obtained under well irrigated treatment, 100% chemical fertilizer and in furrow seed sowing. However, under moderate and severe stress conditions, the highest dry matter yield were obtained in integrated fertilizer application treatments and in furrow sowing. The lowest dry forage yiled was obtained in 100% organic fertilizer treatment and sowing on top of the bed. Under mild and even severe stress conditions, in furrow sowing method in comparison with the top of the bed, the effect of drought stress was mitigated, mainly due to better and longer condition for uptake of moisture and nutrients available for maize plants.

According to the results, it can be concluded that in furrow sowing method, better moisture could be preserved for longer time and optimal application of sugarcane compost as an organic input can improve the physical, chemical and biological properties of the soil, thus providing nutrients, especially nitrogen, and their slow release during the plant growth period which in turn may reduce the negative effect of drought stress and improve growth and yield of forage maize under the conditions of Khuzestan province.

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.