Iranian Journal of Crop Sciences
Year:2011 | Volume:13 | Issue:1 (49)|Papers Count:17

To identify a reliable procedure for studying effects of salinity on sugar beet seed germination under controlled and outdoor conditions as well as to find out the range of salinity concentrations for discriminatiation of genotypic differences for physiological characteristics, three separate experiments were conducted. In the first experiment four levels of salinity (Normal, EC=16, EC=20 and EC=24 dS.m-1) and 20 sugar beet genotypes were studied using factorial arrangement in completely randomized design with four replications. Seedling characteristics as; seed germination, abnormal seedlings, root and hypocotyls length were measured and recorded. The first experiment was a factorial experiment on the basis of a completely randomized design with four replications. The second experiment was carried out in two sizes of Perlits (small and large) as growing media in the greenhouse. It consisted of a tolerant and a susceptible lines that were identified at two EC=16 and EC=20 levels in the previous experiment. In the third experiment, seed germination of 19 sugar beet genotypes were assessed under normal and salt concentrations of EC=16 factorial arrangement in completely randomized design with three replications. Results showed that seed germination was similar in EC=16 and EC=20 dS.m-1 under laboratory conditions and 50% seedling losses was observed at EC=16 dS.m-1 in the greenhouse conditions. Radicle length and number of abnormal plants were determined as useful traits for screening germplasm for salt stress tolernace in laboratory. Sugar beet seed germination decreased to 35% and dead seedlings increased to 80% by growing seeds in sand medium at EC=16 dS.m-1 which showed the importance of sugar beet seedling survival in plant establishment in saline conditions. Seedling growth on Perlit, especially large size, was more vigorous than in sand. Genotypes: Bp Karaj, 7219 p.69, 436 Bigerm, 7233 p.29, 191and hybrid 7233 p.29 × MSc2, 9597 p.12, 428 OT, 452, 8150 p.9 and 7221, were identified as suitable germplasm for further experiments.

Salinity effects on grain yield and some physiological characteristics of two rapeseed (Brassica napus L.) cultivars (Esteghlal and Talaye) were studied under saline conditions. Grain yield of cultivars was compared in a semi-controlled tested plots for two years. Six salinity levels were imposed on a silty loam soil using saline irrigation water. Electrical conductivity of irrigation water was 0.7, 6, 8, 10, 12 and 14 dS.m-1. Grain yield, yield components, harvest index (HI), relative water content (RWC), membrane instability (MIS), and leaf K: Na ratio reduced and leaf Na and Cl significantly (P<0.01) increased in salinity treatments. Leaf K concentration showed a slight change with increasing salinity and the uptake antagonism between Na and K was not observed. Grain yield of Esteghlal severely decreased in salinity treatments. Relative salinity tolerance of these cultivars significantly correlated with plant height, branch number, siliques per plant, grain number.silique-1, leaf Na and leaf K: Na ratio. Results of this study revealed the relationship between leaf K: Na ratio, leaf sodium and relative salinity tolerance in these cultivarss. Relative grain yield of the cultivars were unaffected by soil salinity 4.8 dS.m-1 (ECe) in Talaye and Esteghlal. Each unit increase in salinity above the thresholds reduced the grain yield by 8.8% and 10.4% in Talaye and Esteghlal, respectively. Results of this experiment classified these two rapeseed cultivars in the moderately salt tolerant category.

To investigate the morphological and structural changes of Redroot pigweed (Amaranthus retroflexus L.) in competition with sunflower (Helianthus annus L.) under different timing of seedling emergence, a field experiment was conducted in, Weed Research Department, Iranian Research Institute of Plant Protection in 2008 using Randomized Complete Block Design with three replications. Experimental treatments included five times of emergence for redroot pigweed (with 0, 2, 4, 6, and 8 weeks after sunflower emergence) planted at a density of eight plants per meter of row length. Lateral branch number and length, leaf area in different canopy layers, leaf, stem and head dry mater weights, seed per plant in redroot pigweed and sunflower yield were measured at the end of the growing season. Results indicated that redroot pigweed leaf area; number of lateral branches, branches length, leaf, stem, and head weight significantly decreased with delay- in redroot pigweed emergence. Delayed seedling emergence in redroot pigweed (>4 weeks after sunflower emergence) lost lateral branches and had more leaf area to upper layers of canopy. Increasing the redroot pigweed leaf area index (up to 0.08) and dry matter (up to 10 g.plant-1) increased the seed number.plant-1 up to 4 to 5 folds. Stem and leaf partitioning coefficient, did not vary over all of emergence times for redroot pigweed, but seed partitioning coefficient decreased with delaying seedling emergence. However, the seed yield of sunflower did not decrease in competition with redroot pigweed. In conclusion, weed control in early season (two weeks after sunflower emergence) is suggested to avoid enrichment of redroot pigweed seed bank in the field.

Drought stress is an ever-increasing problem that severely limits crop production worldwide particularly in arid and semi-arid areas. The effect of water stress simulated by polyethylene glycol-6000 (PEG 6000) on K+ uptake and transport responses in two canola cultivars was studied. Based on their plumule and radicle dry weight, AG and PO4 cultivars were selected as the high and the low drought tolerant, respectively. The effect of drought stress (0, -0.29, -0.48 and -0.71 MPa) on K+ uptake and transport in these two cultivars grown in nutrient solutions containing 5 mM KCl was studied. In a second experiment, the rate of K+ uptake from different concentrations of KCl at a fixed water potential (-0.48 MPa) was also studied. Both of experiments were carried out in comletely randomized design in factorial layout with three replications. K+ uptake was determined by flame photometry. Water stress reduced the rates of K+ uptake by the two cultivars. However, the observed reduction was more pronounced in drought stress sensitive cultivar. The rate of K+ uptake by the two cultivars increased by the increase in K+ concentration. Increase in K+ uptake was more pronounced in tolerant cultivar. In the absent of K+, water stress caused K+ endogenous leakage which was greater in sensitive cultivar indicating cell membrane damage by water stress. Results showed that under water stress K+ uptake by canola cultivars was different and K+ alleviated some deleterious effects of drought stress.

To evaluate the effect of application of different levels of nitrogen fertilizer on grain yield and yield components of rice (cv. Khazar), a field experiment was conducted at Rice Research Institute of Iran using a randomized complete block design with 11 treatments and three replications in 2008 cropping season. Nitrogen fertilizer levels (10, 20 and 30 kg.ha-1) were applied according to three chlorophyll meter (SPAD-502) reading thresholds (36, 38 and 40) on fully developed leaf of rice plant. Results showed that the maximum number of tiller.m-2 and tiller fertility was recorded in S40N30 (SPAD40+30 kgN) treatment with 242 tiller.m-2 and 90% tiller fertility. Maximum number of panicle.m-2 was recorded in S38N30 (SPAD38+30 kgN) treatment with 247.33 panicle.m-2, which had not significant difference with other treatments. Mean of highest grain number.panicle-1 (145.17) and maximum panicle fertility (68.51%) was recorded in S40N30 (SPAD40+30 kgN) and S38N30 (SPAD38+30 kgN) treatments, respectively. Highest rate of 1000-grain weight was recorded in S40N30 (SPAD40+30 kgN) treatment (29.60 g), as well as the maximum grain yield with 5559 kg.ha-1. Minimum grain yield was obtained in control treatment (without N) with 3454 kg.ha-1. Maximum milling recovery was also observed in S40N30 (SPAD40+30 kgN) treatment with 68.6% which was 7% higher than the recovery rate in recommended level of fertilizer and 28% greater than control. It can be concluded that splitting of nitrogen fertilizer application at appropriate rate, considering plant requirement, may improve grain yield, yield components and milling recovery in rice.

To evaluate rapeseed grain quality at different maturity stages, an experiment was conducted in the experimental field of Seed and Plant Improvement Institute, Karaj, Iran in 2003-2005 grwoing seasons. Six commercial rapeseed cultivars including; Okapi, Orient, Zarfam, Opera, Licord and SLM046 and five harvesting times including; 50%, 60%, 70%, 80% and 90% siliques maturity of the main stems were studiedusing split plot arrangement in randomized complete block design with three replications. Cultivars were assigned to main plots and harvesting times were randomized in in sub-plots. Chlorophyll contents, oil yield and oil and moisture content of the grain were determined by standard methods. Combined analysis of variance revealed taht the differences among cultivars for the measured traits were significant (P<0.01). Okapi had the lowest chlorophyll content (2.3 mg.kg-1) and the highest oil yield (1661 kg.ha-1) and was superior to other cultivars. Okapi also had the highest (48.7%) oil content. Effect of harvest time on measured traits were significant (P<0.01). Harvesting in 80% maturity of siliques had the lowest (1.9 mg.kg-1) chlorophyll content while the highest oil yield (1548 kg.ha-1) belonged to 90% maturity of siliques. Cultivar × harvest time effects on chlorophyll and moisture contents were significant (P<0.01). Direct and indirect harvesting are suggested at 90% and 70-80% maturity of siliques to maximize grain quality and minimize yield losses.

To investigate the effect of sugar beet leaf age and position on nitrogen content and chlorophyll meter readings (SPAD value) using chlorophyll meter in sugar beet, a field experiment was conducted in the experimental field of Sugar Beet Seed Institute (SBSI) in 2007 cropping serason, using a split-spli plot in time arrangement in RCBD with four replications. Five levels of pre-sowing nitrogen in the form of urea 0 (as control), 120, 160, 200 and 240 kg.ha-1 were assigned to main plots and five plant growth stages considred as sub plots. Chlorophyll meter readings of sugar beet leaf blade number 5, 10 and 15 were determined by chlorophyll meter (SPAD-502) at five growth stages based on the number of leaves including 3-6, 6-12, 12-15, 15-18 and 18-20 leaves of each plant. In the same leaves, concentrations of nitrogen content (Kjeldahl method) and chlorophyll a & b were measured. Analysis of variance showed that main effect of nitrogen fertilizer was significant for SPAD value (P<0.01) and nitrogen content (P<0.05). The main effect of growth stage was also significant for nitrogen content (P<0.05) and specific leaf weight (P<0.01). All measured sugar beet traits were affected by the main effect of plant growth stage. The interaction between nitrogen fertilizer × growth stage was only significant (P<0.05) for leaf nitrogen content. However, the interaction between growth stage × leaf number was significant for all measured traits of sugar beet. There was significant correlation between the SPAD value and nitrogen content of leaf, based on dry weight, in leaf nuber 5, while there was no significant correlation between the SPAD value and nitrogen content of leaf in the leaf number 10 and 15. In conclusion, chlorophyll meter reading and nitrogen content of sugar beet leaves were influenced by leaf age and position.Thus, fully expanded leaf number five may be used for chlorophyll meter reading and determination of nitrogen content in sugar beet in 12-15 leaves stages.

To study integrated weed management in maize cultivar, KSC 704, a field experiment was conducted at the Mahidasht Agricultural Research Station in Kermanshah, Iran.,, during spring and summer of 2006. Split plot arrangement in randomized complete block design with four replications was used.The main plots were row spacing (55, 65 and 75cm) and sub-plots were soil application herbicide (EPTC), non-selective herbicide (Paraquate), mechanical weeding with cultivator, hand weeding and control. Analysis of variance and means comparison indicated that weed biomass in 75 row spacing, in comparison to 55 and 65 cm row spacing, increased by 107% and 105%, respectively. Grain yield in 55 and 65 cm row spacings as compared with 75 cm row spacing increased by 17.6% and 22.5%, respectively. In conclusion, grain yield in EPTC, hand weeding, Paraquate and cultivator treatrments increased by 50%, 47.5%, 31.1% and 28%, respectively. Weeds were controlled better in EPTC and 65 cm row spacing.

Effect of irrigation withhold at different growth stages on grain yield and drought tolerance indices in three safflower cultivars was studied in experimental field of Seed and Plant Improvement Institute, Karaj, Iran, in 2002-2004 cropping seasons. The experimental design was split plot arrangement in randomized complete block design with three replications. Drought stress levels; S1 (blooming and seed development), S2 (blooming and flowering), S3 (blooming), S4 (flowering), S5 (seed development) and S6 (control) were assigned to main plots, and safflower cultivars; Arak 2811, Isfahan local and FO2 were randomized in sub-plots. Combined analysis of variance demonstrated that the highest grain (1258 kg.ha-1) and oil (377 kg.ha-1) yields belonged to Isfahan local in non-stress conditions which was not significantly different from grain and oil yield under S5 drought stress treatment. To evaluate the responses of cultivars to drought stress, different drought tolerance indices, including Stress Susceptibility Indices (STI), Tolerance index (TOL), Mean Productivity (MP), Stress Tolerance Index (STI) and Geometric Mean Productivity (GMP) were calculated. Correlation coefficients showed strong relationship between grain yield in stress and non stress conditions as well as SSI, TOL and GMP indices. MP, GMP, and STI identified Isfahan local as tolerant, and Arak 2811 as susceptible cultivars to drought stress.TOL and SSI also confirmed that Isfahan local as tolerant cultivar for drought stress conditions.

To identify and discriminate 15 soybean commercial cultivars, 11 morphological characteristics viz. plant height, timing of beginning of flowering, timing of maturity, anthocyanin of hypocotyl, growth type, color of hairs on main stem, shape of lateral leaflets, flower color, intensity of brown color of pod, seed coat color due to peroxidase activity, and seed hilum color were assessed and measured. This experiment was conducted during 2007-08 growing seasons using randomized complete block design with three replications in Karaj. Distinctness of cultivars was determined using UPOV’s recommended method for two growing seasons (COYD).Considering seed hilum color, color of hairs on main stem, and flower color soybean cultivars were grouped in similar group. Pair-wise tables were used for discriminating within-group cultivars by other qualitative traits.Analysis of variance for quantitative traits showed very high significant differences (p<0.001) between cultivars.Molecular tests, 16 microsatellite markers were used in cultivars fingerprinting. These markers could distinguish between cultivars except two of them. To determine optimum combination of markers, all markers were used which led to selection of three SSR loci; Satt231, Satt005, and Satt274. These three microsatellite loci with the most discriminative power and effective number of alleles were used in cluster analysis and led to the same distinction results using 16 markers. Since these markers are not influenced by environmental conditions, therefore, could be utilized as complementary traits to morphological and physiological characteristics in identification of soybean cultivars.

Determination of genetic diversity level and genotype relationships is fundamental for identification of desirable parents to be used in different breeding programs. Molecular markers have been successfully used for analysis of genetic diversity in various crops. Genetic diversity among 35 lines and genotypes of barley was studied using 19 pairs of SSR and EST-SSR primers. Totally 157 alleles were produced with an average of 4.06 alleles per locus. Bmag581 with two and Bmag134 with 15 alleles had the lowest and highest allele number, respectively. Polymorphic information content ranged from 0.15 (Bmag518) to 0.89 (Ebmac419) with an average of 0.69. The markers Bamg581 and Ebmac419, had the lowest (0.17) and the highest (0.90) gene diversity, respectively. Cluster analysis based on molecular data assigned the genotypes into five groups. Group 2 genotypes showed low level of tolerance to cold and contained sensitive genotypes. In general, it seems that the studied markers were able to differentiate the most cold sensitive barley genotypes from the rest.

Exploiting advanced breeding materials to accelerate the development of new cultivars by breeders has created global concern about the narrow genetic basis of modern wheat cultivars. This is in contrary with the extensive genetic diversity stored in plant gene banks. Therefore, identifying landraces with useful characteristics would be of great value. Seventeen accessions of wheat collection of the National Plant GeneBank of Iran together with three check varieties, Kavir, Mahooti and Roshan, were evaluated in four different conditions; normal irrigation and irrigation ceased at different growth stages of; stem elongation (E1), heading (E2) and grain filling (E3) in 2007-2008 grown season. The highest grain yield belonged to genotypes 3, 2 and 15 in non-stress condition, 13, 11 and Mahooti in E1, 15, 11 and 1 in E2 and 2, 1 and 5 in E3. Genotypes 3 and 15 located at A region of Fernandez diagram in all three stress conditions and were superior to other genotypes, based on stress tolerance indices. Genotypes 4 and 11 had the lowest yield loss due to stress at grain filling as compared to non-stress condition and stress at heading, respectively. MP, GMP and STI were identified as the most favorable indices for all three stress conditions; E1, E2 and E3. Cluster analysis grouped the genotypes in 5, 3 and 4 groups at E1, E2 and E3 conditions, respectively. Results indicated that tolerant genotypes should be identified according to the growth stage at which the drought occurred.

Starch comprises about 90% of milled rice, therefor the eating and cooking quality of rice is mainly affected by the starch properties. The eating and cooking quality of rice has usually been evaluated by three major physical and chemical properties of the starch including; amylose content, gel consistency and gelatinization temperature. In addition, other important properties of starch, such as paste viscosity have been established to evaluate more precisely the cooking quality of rice. To determine the general and specific combining ability of starch paste viscosity properties in the parental lines, five restorers and four cytoplasmic male strile (CMS) lines were selected as lines and testers, respectively. These CMS and restoring lines were a random sample of parents from a reference population of rice breeding materials in Iran. Nine parents were crossed in a Line × Tester crossing system in 2005. Twenty F1 hybrids and their parents were evaluated in a randomized complete block design with two replications for evaluating paste viscosity characteristics. The paste viscosity properties were determined by the Rapid Visco Analyzer. General combining ability (GCA) and specific combining ability (SCA) were determined by Kemptrhone method. In this study, mean of the parents and hybrids were also compared with the local rice varieties for paste viscosity properties based on 95% confidence interval. The results revealed that effects of GCA and SCA were significant for all of the paste viscosity properties. The additive effect was greater than dominance and environmental effects for all of the paste viscosity properties, except pasting temperature. For this parameter, environmental effect was high. All of the parents were out of the confidence interval of the pasting properties. Therefore, they were not suitable for cooking and eating quality.However, among the crosses, five hybrids SA15A×IR53R, IR79124A×SepidroodR, SA15A×SA14R, IR79124A×IR53R and IR58025A×SA14R were in the confidence interval of the pasting characteristics based on the paste viscosity properties, and had good cooking and eating quality similar to local rice varieties.

To determine relationships between seed oil and protein contents with some important agronomic traits, 364 soybean genotypes were evaluated using an augmented design in Seed and Plant Improvement Institute, Karaj, Iran, during 2004 growing season. Most agronomic traits had significant negative correlation with seed oil content, except number of seed.pod-1. However, most agronomic traits had highly significant positive correlation (p<0.01) with seed protein content, except seed oil content and number of seed.pod-1. Results of stepwise regression and path analyses showed that seed protein content and days to beginning of flowering had direct negative effect, and 100 grain weight had direct positive effect on grain oil content. Oil content and biomass also had direct negative effect, and 100 grain weight had direct positive effect on grain protein content.Canonical correlation analysis for seed yield and seed quality variables led to introduction of two pairs of variables. The first pairs was named "grain yield and number of grain.plant-1 " and "grain oil content" and the second pairs was named "grain yield and number of pod.plant-1 " and "grain protein content", respectively.

A complete set of diallel crosses among seven durum wheat lines were used to study the genetics of yield and its components. Eight traits including days to heading, harvest index, grain number.spike-1, grain weight.spike-1, grain number.plant-1, plant height and grain yield.plant-1 were measured and recorded. Significant (P<0.01) differences were observed among genotypes for all the studied traits. Assumptions of Jinks-Hyman method were valid for harvest index, grain number.spike-1, grain weight.spike-1 and grain yield.plant-1. However, for the remaining traits, when one parent was excluded, the assumptions fulfilled. Based on the estimates of average degree of dominance and result of graphical analysis, the gene action for days to heading, was partial dominance, while grain weight.spike-1, plant height, fertile tiller number, grain number.spike-1, grain number.plant-1, grain yield.plant-1 and harvest index were controlled by over dominance gene action. Hayman analysis of variance indicated that additive (a) effects were significant for all of the studied traits, and dominance (b) effects significant for all of traits except day to heading. Maternal effects (c) were also significant for all of traits except plant height and fertile tiller number. Broadsense heritability estimates ranged from 0.93 (for grain number.spike-1 and grain weight.spike-1) to 0.70 (for plant height). Narrow-sense heritability estimates ranged from 0.70 (for days to heading) to 0.30 (for fertile tiller number).The biplot indicated that entry Prion-1 had the highest GCA effect for grain weight.plant-1, fertile tiller number, grain number.plant-1, grain yield.plant-1 and harvest index. However, it had the lowest GCA for plant height and days to heading. Therefore, this genotype can be considered as suitable parent in durum wheat breeding programs.