SEED QUALITY ( Fe AND Zn CONTENTS ) OF WHEAT GENOTYPES

In the lab study, seeds of 18 wheat genotypes were tested for their concentrations and contents of Fe and Zn to determine the seed quality . The iron concentrations in the seed of the 18 wheat genotypes ranged between 20.5 to 65.4 mg kg -1 dry weight basis. Only the seed of Saef and Bohuth/6 genotypes had Fe concentration more than 57 mg Kg -1 and fulfill quality standard set by WHO, 2006, were as six of seed genotypes had more than 41mg Zn Kg -1 namely Saef, Karoniah, Zebba/5, Abo-Ghraib, Sham/3 and Pash/29. The results also showed that for the two genotypes with the highest Fe concentration, only Saef was the genotype that had higher Zn concentration more than 41 mg Zn Kg -1 the quality standard. In contrast to Zn , the variation for seed Fe content was not greater than variation found for the concentration.


INTRODUCTION
Micronutrient deficient soil is critical issues in the developing countries (Iraq is one of them), and result in severe impairments of human health and developments (Pinstrup-Anderson, 1999, Welch andGraham 2000).In humans deficiencies of essential micronutrients such as iron and zinc are wide spread.In many regions of the world, a large proportion of dietary intake of these nutrients is derived from grains.More than three billion people globally suffer from Fe and Zn deficiencies (Cakmak et al., 2002).In plants Fe and Zn deficiency often occurs in calcareous soil where chemical availability of Fe and Zn to plant root are extremely low.Correction of Fe or Zn deficiency are not always easy through the use of Fe or Zn fertilizers because of their extremely poor solubility.Remediation of Fe and Zn deficiencies in calcareous soils by fertilizers only is a costly and time consuming management .Therefore we think that screening for micronutrientsefficient varieties for micronutrients deficient soil with a combination of mineral fertilizers and larger seed size (with higher Fe and Zn content) is an important practical approach for the correction or avoidance of Fe and Zn deficiencies in cereals (Welch, 1986;Rengel and Graham 1995) leading to higher yield.To our knowledge, until now in Iraq no data are available about seed micronutrient contents.The present study was conducted to assess the Fe and Zn concentration and contents of different wheat genotypes to provide an insight into the quality of the seed for human consumption and it's resowing for better crop harvest.

Seed preparation and micronutrients concentrations and contents determination:
The lab study conducted to determine seed quality (Micronutrients content) of 18 new wheat genotypes brought from ICARDA (International Center for Agricultural Research in the Dry Areas, Syria.The Fe and Zn concentrations and contents of each genotype were determined.The method described by Chapman and Pratt (1961) was used to measure the seed-micronutrient concentration.Seeds weights of all genotypes were measured.The data were statistically analyzed by analysis of variance and F tests.Significance of differences between means was evaluated by the least significant difference test (Adj.LSD) at the 0.05 level of probability.

RESULTS AND DISCUSSION
Iron concentrations and content: Iron concentrations in the seed of different wheat genotypes ranged between 20.5 to 65.40 mg kg -1 on dry weight basis (Table 1).The highest Fe concentration (65.40 mg kg -1 ) was recorded in the seed of Saef genotype, whereas the lowest Fe concentration of 20.5 mg kg -1 was exhibited by Doma/1 variety.The genotypes Bohuth/6, Abo-Ghraib, Sham/8, Bohuth/7, Adil/3, Bohuth/4, Jawaher, IPA/99 and Tilaafar also proved to be the higher accumulator of Fe and good Fe absorber as compared with other wheat genotypes.The lowest Fe concentrations in the seeds of the genotypes Zebba/5, Asel, Karoniah, Acsad/65, Sham/3, Haama/14, Pasha/29 and Doma/1 (Table 1) suggest either severity of Fe deficiency problem in the region of these varieties or lower Fe efficiency of these genotypes.These results are in agreement to those obtained by Rengel and Graham (1995) and to those obtained by Imtiaz et al., (2003).Iron contents per seed have been presented in (Table 1).The genotypes exhibited significant variations in Fe contents of their single seed.Iron contents within the seed ranged between 1.136 μg seed -1 to 2.871 μg seed -1 , when calculated on oven dry weight basis.As with Fe concentrations, Fe contents were also higher in the seed of Saef, Bohuth/6, Jawaher, Abo-Ghraib, Bohuth/7, IPA/99, Tilaafar/3, Sham/8, Adil/3 and Bohuth/4 genotypes than the other genotypes.The amount of micronutrients in grain depends on the amount taken up by the roots during grain development and the amount redistributed in the grain from vegetative tissue by the phloem.The amount of each nutrient element remobilized by the phloem is greatly dependent on the phloem mobility of each element (Garnett and Graham 2005).Kochian (1991) investigated Fe transport into remobilization from leaves and found that iron has intermediate phloem mobility.Zinc showed good remobilization, whereas Mn remobilization was poor (Pearson and Rengel 1994).Zinc concentration and content: The wheat genotypes were exhibited significant variations in the zinc concentrations of their seeds (Table 2).Zinc concentrations in the seed of different wheat genotype ranged between 4.73 mg Zn kg -1 to 53.30 mg Zn kg -1 on dry weight basis.The highest Zn concentration (53.30mg kg -1 ) was recorded in the seed of saef genotype, whereas the lowest Zn concentration of (4.73) mg kg -1 ) was exhibited by Sham/8 genotype, followed by Bohuth/6, Tilaafar/3, Haama/14, Bohuth/4, Acsad/65, Adil/3 and Asel genotypes.The higher seed Zn concentration genotype proved to be higher accumulator of Zn as stated by Rengel  and Graham (1995).Zinc contents per seed have been presented in (Table 2), and ranged between 0.168 μg seed -1 to 2.34 μg seed -1 when calculated on oven dry weight basis.The genotype Saef showed the highest zinc content followed by Karoniah, Abo-Ghraib and both Pasha/29 and Jawaher genotypes as compared with the other 13 genotypes.Grain quality standards: Based on personal daily requirement of Fe and Zn, and the information of bioavailability provided by the WHO (2006) the concentrations of Fe and Zn have been proposed to be elevated to 57 and 41 mg Kg -1 respectively.These quality standards were used by Zhang et al., 2010 andImtiaz et al., 2010.Only Saef and Bohuth/6 from the 18 genotypes used infulfill the quality standard set by WHO, 2006 and had high Fe concentration more than 57 mg Kg -1 and it was found that the other 16 genotypes had low Fe concentration less than 57 mg Fe Kg -1 (Table 1) , where as six of genotypes had higher Zn concentration more than 41 mg Zn Kg -1 namely Saef, Karoniah, Zebba/5, Abo-Ghraib, Sham/3 and Pasha/29 (Table 2).For the two genotypes with the highest Fe concentration, only Saef was the genotype had higher Zn concentration more than 41mg Kg -1 .Therefore, there is sufficient genetic variability to develop wheat genotypes with increased Zn levels in the grain and promising genetic variability for Fe.
Information on mineral nutrient reserves in seed should be perfect from agricultural point of view and human requirements as well.It could provide an insight into these genotypes which are high mineral element accumulators, and can best be utilized for human consumption as well as agricultural production.The high concentrations of Fe and Zn for Saef and Abo-Ghraib (Tables 1, 2) ranked it as the leading genotypes in Fe and Zn concentration, and this made it the most promising genotypes.Table (3) provides total amount of Fe and Zn per seed (content) in addition to the Fe and Zn concentrations in seeds of wheat genotypes.The variation for Zn content in seed was much greater when compared to the variation found for the concentration.This indicates large differences for seed weights among genotypes by contrast; the variation for Fe content was not greater when compared to the variation found for the concentration.

Table ( 1
): Iron concentration (mg Kg -1 ), seed weight and content in the seed (original seed size) of 18 wheat genotypes used in the present study.

Table ( 2
): Zinc concentration (mg kg -1 ), seed weight and content in the seed (original seed size) of 18 wheat genotypes used in the present study.