M. T. Assad

Shiraz University, Shīrāz, Fars, Iran

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Publications (19)18.22 Total impact

  • Iran J. Field Crops Sci. 01/2009; 40:1-9.
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    ABSTRACT: Sequential extraction has been used as a suitable method for identification of chemical forms of trace elements and their plant availability. However, in calcareous soils of Iran, little attention has been paid to studying the capacity of soil components for cadmium (Cd) retention and the change in chemical forms as affected by time. The objective of this study was, therefore, to determine the effect of incubation time, soil texture, and application of enriched compost on chemical forms of Cd. The textural class of a clay loam calcareous soil [Fine, mixed (calcareous), mesic Typic Calcixerepts] was converted to sandy loam by adding acid-washed pure quartz sand and both the original clay loam and the produced sandy loam were treated with 30 g kg−1 of municipal waste compost (MWC). The compost had been enriched with different amounts of CdSO4 to obtain Cd concentrations ranging from 5 to 60 mg Cd kg−1 in treated soils. The treated soils were placed in plastic containers and incubated at 25±2 °C near field capacity moisture. After 0, 1, 2, 4, 8, and 16 weeks, a sequential extraction scheme was used to fractionate Cd of incubated samples into soluble+exchangeable (Sol+Ex), carbonate-bound (Car), organically bound (OCd), Mn-oxide-bound (MnOx), amorphous Fe-oxide-bound (AFeOx), crystalline Fe-oxide-bound (CFeOx), and residual (Res) forms. Results showed that, depending on the textural class, about 82–88% of Cd was converted to Sol+Ex, Car, and OCd forms. In both soils, carbonate fraction was dominant. The conversion of applied Cd to Sol+Ex and Car in the sandy loam was higher than in the clay loam, whereas the reverse was observed for other Cd forms. The CFeOx was less than the detection limit of atomic absorption in both textural classes. Increasing the Cd rate increased all forms of Cd but the % increase depended on the capacity of different soil components for Cd retention. Carbonate showed the highest capacity for retention. Incubation time had a significant effect on Cd forms. However, in almost all treatments, more than 80% of added Cd was converted to Car and OCd immediately, and the proportion approximately stayed the same throughout the course of experiment. Although the presence of a large amount of cadmium in the first three steps of extraction procedure shows a relatively high Cd bioavailability in soils under study, it can be concluded that the calcareous nature of these soils plays a key role in cadmium retention because a major portion of the soluble Cd entered carbonate fraction immediately after addition to soils.
    Geoderma 01/2006; 136(3):533-541. · 2.35 Impact Factor
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    ABSTRACT: Highly calcareous soils are abundant in Iran. The calcium carbonate equivalent (CCE) of these soils reach up to 650 g kg. Although phosphorus (P) fertilizer is being widely used in these soils, little information, if any, is available about P status in such soils. The objectives of this study were to 1) determine inorganic P forms in 18 surface soils of southern Iran, 2) study P readsorption during different stages of fractionation schemes, 3) assess the ability of NaOH to extract aluminum (Al)‐P, and 4) evaluate the relationships between P availability indices and inorganic P forms. Eighteen soil samples with a wide range of physicochemical properties were selected for this study. Inorganic P forms was determined by sequential extraction with NaHCO3, NH4OAc, NH4F, NaOH, citrate dithionite (CD), and H2SO4, which are referred to as Ca2‐P, Ca8‐P, Al‐P, Fe‐P, occluded P (O‐P), and Ca10‐P. Phosphorus readsorption in different stages was determined by 1 M MgCl2. Furthermore, a fractionation scheme without an NH4F step was used to evaluate the ability of NaOH to extract Al‐P. NaHCO3 (Olsen‐P) and MgCl2‐extractable P (Exch‐P) were regarded as P-availability indices. The abundance of different P forms was in the order Ca2‐P
    Communications in Soil Science and Plant Analysis - COMMUN SOIL SCI PLANT ANAL. 01/2006; 37:1877-1888.
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    ABSTRACT: Desorption of copper (Cu) is an important factor in determining Cu availability in calcareous soils. Kinetics of native and added Cu desorption by DTPA (diethylene‐triaminepentaacetic‐acid) from 15 highly calcareous soils of southern Iran were studied in a laboratory experiment. Our results showed that two constant‐rate, Elovich, simple Elovich, and parabolic‐diffusion equations were the best‐fitted equations among eight kinetic models used. The copper desorption pattern based on the parabolic‐diffusion equation revealed that the rate of native Cu desorption was higher in the first 2 h followed by a slower release rate, which suggests that two different mechanisms are involved. The trend may describe why the DTPA soil test has been considerably successful in predicting Cu availability in calcareous soils. Stepwise multiple regression equations indicated that CCE (calcium carbonate equivalent), CEC (cation exchange capacity), and clay content are the most important soil characteristics that predict the rate constants of the kinetic models. Mean extractant recovery percentage (ERP) of the soils was only 20%, which indicated that after 20 days, DTPA extracted only one‐fifth of added Cu. Regression equations indicated that as soil OM (organic matter) content increased, the value of ERP decreased. From results reported herein it seems that CCE, CEC, and clay are the most important factors controlling Cu release from highly calcareous soils of southern Iran. However, the initial soil Cu desorption rate is probably controlled by CEC.
    Communications in Soil Science and Plant Analysis 01/2006; 37(5-6):797-809. · 0.42 Impact Factor
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    Modarresi M, M. T. Assad, Kheradnam M
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    ABSTRACT: Yield is a quantitative trait and improving grain yield through direct selection is time-consuming. Indirect selection consisting of selection indices is more promising. A field experiment was conducted during 1999-2000 growing season in two experimental locations (Kooshkak and Badjgah) of College of Agriculture, Shiraz University, Shiraz. Thirteen corn hybrids were used in a randomized complete block design with three replications in each location. Thirty-five traits were measured in five developmental stages (stem elongation, tasseling, blister, hard dough and physiological maturity) and combined analysis of variance and covariance were conducted. Finally, 12 traits were selected for constructing selection indices via path analysis. Two optimum selection indices were used in this experiment. In both selection indices, different combinations of traits applied as linear function (multivariate linear model) and coefficients of traits in combinations were calculated. The coefficient of indices were obtained from: b=P-1Ga, where b is the vector of index coefficients, P-1 is the inverse of phenotypical variance and covariance matrix, G is the matrix of genotypical variance and covariance and a is the column vector of traits heritability. In the first index, heritability of traits with the same sign was used as economic values. Selection index including grain yield and net assimilation rate in the second stage (NAR2) was the best. In the second index, the sign of genotypic correlation with yield was given to economic values. Finally, selection index including grain yield and NAR2 was the best, too. In both selection indices, correlation of selection indices with genotypic value was equal to 1. This was 14% higher than the first index including yield alone. In both selection indices, physiological indices including net assimilation, crop growth, and relative growth rates were the most important traits comprising the best selection indices.
    Journal of Science and Technology of Agriculture and Natural Resources. 01/2004;
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    ABSTRACT: Twenty-five surface samples of calcareous soils of Fars Province were used to study the distribution of different nitrogen (N) forms to determine the relationship between the N forms and soil charcteristics, and to obtain regression equations for prediction of N forms from soil characteristics. The forms determined were: soil total nitrogen; NO3-N by phenol disulfunic acid; NO3-N extractable by 2 M KCl; NH4-N extractable by 2 M KCl, 1 N sulfuric acid, and 0.25 N sodium hydroxide; oxidative released N by acid permanganate and alkaline permanganate; and NH4-N extractable by 2 M KCl at 100 oC. The highest amount of N was that released by alkaline permanganate which constituted 4.47% of soil total N and the lowest form was exchangeable NH4+ which amounted to only 0.6% of total N. Water soluble and exchangeable forms accounted for less than 2% of total N. Highly significant correlations were found between total N and acid permanganate-N (r=0.931) and total N and alkaline permanganate-N (r=0.850). Highly significant regression equations were obtained for prediction of soil total N, acid permanganate-N, and alkaline permanganate-N from soil organic matter (OM), which is an indication of a close relationship of these N forms with OM.
    Journal of Science and Technology of Agriculture and Natural Resources. 01/2004;
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    ABSTRACT: Application of nitrogen (N) fertilizers without knowing the nitrogen supplying capacity (NSC) of soils may lead to low N use efficiency, uneconomical crop production, and pollution of environment. Twenty-five surface (0–20 cm) soil samples (pH 7.9–8.3; organic matter 7.8–35.0 g kg; calcium carbonate equivalent 253–648 g kg) from cultivated lands of Fars Province of Iran were used in laboratory and a 6-week greenhouse experiment to compare seven methods of estimating NSC of calcareous soils. The methods used were (i) determination of –N produced following the anaerobic incubation of soils; (ii) determination of –N extracted from soils by 2 M KCl; (iii) determination of –N extracted from soils by H2O; (iv), (v), (vi) measuring the amount of ultraviolet (UV) light absorption by soil extracts at 200, 205, and 260 nm; and (vii) determination of –N from the “second derivative” of light absorbance of soil extracts in the range of 200–280 nm. The soils, provided with sufficient nutrients other than N, were planted with corn (Zea mays L., cv Single Cross 704) and total N taken up by aerial parts of the plants was taken as the NSC of soils. Regression equations obtained between plant N uptake and each of the methods showed that absorbance at 205 nm was the best method, predicting 70.5% of the variabilities in NSC, when used alone. The “second derivative” method, when used along with organic matter and clay contents of the soils, predicted 84.2% of the variabilities in NSC. It is suggested that UV absorption methods be considered as a measure of NSC because they are more rapid, less laborious, and consume less chemicals than biological and conventional chemical methods.
    Communications in Soil Science and Plant Analysis 01/2004; 35(Nos. 1 & 2):219-232. · 0.42 Impact Factor
  • A.  ESTAKHR , M. T.  ASSAD 
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    ABSTRACT: The availability of more resistance genes to Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko) may provide additional protection from new virulent strains or biotypes of the insect. This genetic study was conducted to determine the allelic relationships of resistance genes in two Iranian wheat (Triticum aestivum L.) lines, SHZ.W.102 and SHZ.W.104 and lines PI 137739, PI 262660, PI 372129, PI 294994 and PI 243781, carrying resistance genes Dn1, Dn2, Dn4, Dn5 and Dn6 respectively. The two Iranian lines were crossed to each of the other resistant lines, and F1 and F2 seedlings were screened for RWA reaction. The resistance gene in 102 was allelic to Dn1, however, the resistance gene in 104 was different from other known genes. The resistant line 104 is an effective source of genetic resistance to RWA and the gene symbol Dn7 is proposed for its resistance gene.
    The Journal of Agricultural Science 04/2002; 138(03):281 - 284. · 2.88 Impact Factor
  • M.T. Assad, G.M. Paulsen
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    ABSTRACT: Increased grain yield potential of newcultivars of wheat (Triticum aestivumL.) is attributed to morphological traits,but actual yield is determined mostly byenvironmental conditions. Our objectivewas to ascertain the contribution ofresistance to freezing, high temperature,drought, and defoliation to advances inyield of landmark cultivars of winter wheatin the U.S. Great Plains. Eight cultivarsthat represented significant improvementbetween 1874 and 1994 were compared bystandard electroconductivity measurementsof stability of seedling cell membranes tofreezing, high temperature, and desiccationand by grain yield and its components inplants subjected to freezing during theseedling stage and to high temperature,drought, and defoliation during maturation. Genetic changes relative to `Turkey'(introduced 1874) in stability of cellmembranes to freezing, high temperature,and desiccation were small andinconsistent. Advances in grain yieldunder control conditions were similar togains in field studies. Most cultivars hadlittle genetic change in yield afterfreezing, drought, or defoliation, probablybecause high levels of resistance areincompatible with high yield potential andthe stresses are episodic. Genetic advancein grain yield under high temperature wasphenotypically correlated with change inyield under control conditions, suggestingthat the trait is essential forproductivity because of the ubiquitousoccurrence of the stress in the region. Weconcluded that changes in resistances tofreezing, drought, and defoliationcontributed little to advances inproductivity of winter wheat in the GreatPlains, but that resistance to hightemperature was important for new cultivars.
    Euphytica 01/2002; 128(1):85-96. · 1.64 Impact Factor
  • Experimental Agriculture 01/2002; 38:389-395. · 1.06 Impact Factor
  • M. T. ASSAD
    Plant Breeding - PLANT BREED. 01/2002; 121(2):180-181.
  • H. R.  DORRY , M. T.  ASSAD 
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    ABSTRACT: Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko) has caused significant losses to wheat and barley in many parts of the world. Two RWA resistant lines with flat leaves were crossed with each other and with two RWA susceptible lines producing rolled leaves when infested with RWA. F1, F2 and BC1F1 seedling leaves were classified according to their leaf shape as flat, longitudinally folded, or rolled after artificial infestation. Leaf chlorosis in the phenotypes of F2 plants was also recorded.
    The Journal of Agricultural Science 08/2001; 137(02):169 - 172. · 2.88 Impact Factor
  • M.T. Assad, H.R. Dorry
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    ABSTRACT: Russian wheat aphid (RWA), Diuraphis noxia (Kurdjumov), is a serious pest of small grains in many countries. A previous study screened 70 genotypes, collected from different parts of Iran, for RWA resistance. Four crosses were made between two resistant lines (Shz.W-102 and Shz.W-104) and two susceptible lines (Shz.W-101 and Shz.W-103). Parents, F1, F2, and BCF1 seedlings were screened for RWA resistance in the greenhouse by artificial infection. To determine allelism, the two resistant lines were intercrossed and F1, and F2 seedlings were evaluated. Resistance in Shz.W-102 and Shz.W-104, when crossed with Shz.W-101, was controlled by one dominant gene. However, resistance in Shz.W-102 and Shz.W-104, when crossed with Shz.W-103, was controlled by two dominant genes. Genes in two resistant lines segregated independently of each other. A three-gene system was proposed to govern resistance in the lines under study .
    Euphytica 01/2001; 117(3):229-232. · 1.64 Impact Factor
  • Iran J. Agric. Sci. 01/2000;
  • Iranian Journal of Agricultural Science. 01/2000; 31:839-850.
  • H. Razi, M.T. Assad
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    ABSTRACT: Research was conducted to study interrelationships between agronomic and seed characters and their direct and indirect effects on seed yield per plant under normal and limited irrigation regimes. Two field experiments were conducted in 1996 at the Experimental Station of College of Agriculture, Shiraz University at Badjgah. Fourteen sunflower (Helianthus annuus L.) cultivars consisting of eight hybrids and six open pollinated varieties were grown in two randomized complete block designs with four replications. Two experiments differed in respect to irrigation regime. The cause and effect relationships of 12 different characters were assessed. Most of the characters including seed yield and oil content showed considerable genotypic and phenotypic variations. Water stress significantly decreased yield and its components, however, oil content did not differ significantly. Genotypic and phenotypic correlations revealed that seed yield had significant positive correlations with days to flowering, days to physiological maturity, head diameter, plant height, 1000-seed weight and oil yield under normal and limited irrigation. Seed yield had significant correlations with oil content and kernel percentage under normal irrigation regime, while these correlations were largely reduced under stress conditions and were not significant. The highest direct effect, was exhibited by 1000-seed weight and number of filled seeds per head in normal and limited irrigation environments. However, cause and effect relations of other traits with seed yield changed due to irrigation conditions. Direct effect of oil content was quite lower than its correlation with seed yield. The lowest direct effect was found for plant height and oil content under normal and stress environments, respectively.
    Euphytica 12/1998; 105(2):83-90. · 1.64 Impact Factor
  • S. Golestani Araghi, M.T. Assad
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    ABSTRACT: Drought is one of the important factors limiting crop production in arid and semi-arid regions. Four drought resistance criteria, consisting of canopy temperature, stomatal resistance, transpiring area and rate of water loss by excised-leaves were examined in two experiments conducted in optimum and stress moisture conditions in 1995. A randomized complete block design with four replications and six genotypes was used for each experiment. Under optimum moisture conditions, there was a significant difference in canopy temperature at midday between drought resistant and drought sensitive genotypes. A significant linear relationship was also obtained between this criterion and yield reduction ratio as determined by Yr = 1-(Ys/Yp) (Ys and Yp = yield under stress and non-stress conditions, respectively), at the ear emergence stage. The only significant difference between cultivars in respect to stomatal resistance in stress conditions was that of adaxial leaf surface in ear emergence stage. No significant linear relationship was obtained between transpiring area and yield reduction ratio. Cultivars differed in respect to rate of water loss (RWL) and initial water content (IWC) in ear emergence and grain filling in stress environment only. Ultimately, three criteria namely canopy temperature, stomatal resistance and RWL, in explicated conditions were recognized as benificial drought resistance indicators.
    Euphytica 01/1998; 103(3):293-299. · 1.64 Impact Factor
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    ABSTRACT: Manganese (Mn) becomes a limiting factor of plant growth under some soil conditions. High pH and abundance of free calcium carbonate in calcareous soils are conducive to Mn‐deficient plants. The Mn status of highly calcareous soils in Iran has not been studied in detail. This experiment was conducted to obtain such information. Twenty‐three surface (0–20 cm) soil samples with pHs from 7.7 to 8.2 and calcium carbonate equivalent (CCE) from 19 to 46% were used in a 7‐week greenhouse study with soybean [Glycine max (L.) Merr.]. The experiment was a 23 × 3 factorial with three replicates, i.e., 23 soils and 3 Mn levels (0, 15, and 30 mg/kg soil as manganese sulfate). Extractable Mn of the untreated soils were determined before planting by nine different procedures. Dry matter yield, Mn concentration of soybean tops, and Mn uptake were used as the measure of plant response. Multiple regression equations showed that the most influencial soil properties in extractability of Mn in highly calcareous soils are cation exchange capacity (CEC) and calcium carbonate equivalent (CCE). Application of Mn increased dry matter, Mn concentration and Mn uptake of soybean plants in most soils. The Mn concentration of plants on some of the soils, however, decreased following the application of Mn. This was attributed to dilution effect caused by enhanced growth. The recovery of applied Mn in all soils was low, persumably due to conversion of the applied Mn to unavailable forms. Regression equations were developed to predict dry matter, Mn concentration, and Mn uptake by plants from soil Mn extracted by water, hydrochloric acid, disodium‐EDTA, and EDTA‐ammonium acetate.
    Communications in Soil Science and Plant Analysis - COMMUN SOIL SCI PLANT ANAL. 01/1995; 26:1441-1454.
  • F. Hassani, M. T. Assad
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    ABSTRACT: Wheat streak mosaic (WSM) caused by wheat streak mosaic virus (WSMV) is a serious disease of wheat and many plants in the grass family. In previous studies genotypes collected from different parts of Iran, were screened for WSM resistance. Two resistant genotypes, Adl Cross and 4004 were crossed to one susceptible genotype Marvdasht. Reciprocal crosses were also made. Seedlings of parents, F1, F2, backcrosses to susceptible (BCS) and resistant (BCR) were evaluated for WSMV reaction based on scales 0–7, by artificial infection under greenhouse conditions. Allelism was studied by evaluating the F1 and F2 seedlings of the resistant resistant cross. Inheritance of resistance to WSMV in Adl Cross and 4004 was controlled by one dominant gene. No allelism was observed between resistance genes. Among the F2 seedlings of the resistant resistant cross relatively more resistant genotypes with a zero score were observed. These two genes, therefore, can be incorporated into an adapted wheat cultivar to produce a more durable resistance.
    Euphytica 140(3):213-216. · 1.64 Impact Factor