Water deficit is one of the most common constraints to crop productivity in the world and Iran. In order to study effect of drought stress on morphologic traits, yield and yield components of 34 hybrids of corn, an experiment was carried out based of complete randomized block design with three replication under F.C. irrigation and drought stress in Khorasan Razavi Agricultural Research and Natural Resources Institute mashhad,Iran on 2010. Results of analysis of variance showed that in both conditions there are significant different between all hybrids for all traits. In these experiment drought tolerance indices as TOL, MP, GMP, SSI, STI, HARM and also Golden Mean (new index) were calculated. Results of hybrid means comparison showed that in F.C. Irrigation condition S.C500 hybrid and in stress condition N.11 hybrid was better than others in yield trait (13/79 and 5/69, respectively). It seems that Harm, STI, MP and GMP indices have a similar ability to separate drought sensitive and tolerant genotypes. According to cluster analysis (UPGMA method) based on stress tolerance and susceptibility indices and grain yield in both F.C. and stress conditions, hybrids were classified in three groups with low intra- and high extra-group similarities. In conclusion, it can be suggested that H11 and SC250 hybrids should be recommended in Mashhad Plain.

Agrobacterium tumefaciens mediated transformation may offer a better alternative than the biolistic gun for genetic transformation of MAIZE plants. This gene delivery system results in a greater proportion of stable, low-copy number transgenic events than does the biolistic gun, and is highly efficient. In the present work, we studied MAIZE transformation using A. tumefaciens by identifying some important factors that affect transformation efficiency subsequent tissue culture and regeneration of transgenic plants. Although, all genotypes produced embryogenic calli, S61 and A188 lines had higher percent (75% and 71% respectively) of regeneration than the other ones. Transformant events obtained when immature embryos (1.5-2 mm) were inoculated with A. tumefaciens LBA4404 harboring a standard binary vector pCAMBIA3301 after 72 h pretreatment culture of the embryos. Polymerase chain reaction (PCR) confirmed the presence of the gus and bar genes in the genome of regenerated plants. The transformation frequency (the number of independent, PCR-positive transgenic plants per 100 embryos infected) was 6.45% for S61 genotype. Therefore, our results identified suitable genotype (S61), embryo size (1.5-2 mm), A. tumefaciens strain (LBA4404), pretreatment culture, and appropriate antibiotic (Timentin) for Agrobacterium mediated transformation of Z. mays.

In order to investigate the effects of seed priming with plant growth promoting rhizobacteria (PGPR) on phyllochron and leaf appearance rate of corn, a factorial experiment based on randomized complete block design with three replications was conducted at the Research Farm of University of Mohaghegh Ardabili in 2008. Factors were: three corn cultivars (SC-404, SC-410 and SC-434) and seed priming with plant growth promoting rhizobacteria in four levels (without priming, seed priming with Azosprilium, seed priming with Azetobacter and seed priming with Azosprilium+Azetobacter). The results showed that phyllochron, time between the appearance of successive leaves on a shoot, was significantly affected by corn cultivar, seed priming with plant growth promoting rhizobacteria and interaction between of seed priming and corn cultivars. Seed priming with Azetobacter decreased the phyllochron but increased rate of leaf appearance. Response of corn cultivars was different to these characteristics.Leaf appearance rate in SC-404 was more than SC-410 and SC-434. The highest leaf appearance rate and the least of time for phyllochron were obtained with seed priming of SC-404 cultivar with Azetobacter. Leaf area index was increased due to seed priming with Azetobacter. In all of priming levels, process of variances leaf area index was similar until 37 days after sowing. From 44-65 days after sowing reached to a maximum level (4.96) and then decreased slowly till 79 days after sowing. This might be related to increasing aging of leaves, shadding and competition between plants for light and other resources. The highest leaf area index obtained in treatment combination of seed priming of SC-404 cultivar with Azetobacter and the least of it was in without priming.Number of leaf per plant and leaf dry matter increased in seed priming with Azetobacter.Thus, it is suggested that in order to increase leaf appearance rate, number of leaf per plant and leaf area index, seeds priming of SC-404 cultivar with Azetobacter be applied in conditions of Ardabil Plain.

This experiment was conducted to study the effects of water deficit stress on morphological traits, yield and yield components of 60 MAIZE single cross hybrids at Torough Agricultural and Natural Resources Research Center located in Mashhad, Iran on 2013. This experiment was laid out in randomized complete block design with three replications. The irrigation treatments were consisted of two irrigation levels (50 and 80 percent allowed water depletion as normal and drought stress, respectively). The result of ANOVA showed significant differences among single cross hybrids for all of measured traits in both conditions. In non-stress or normal condition, hybrids No.4 and in stress condition, hybrids No.9 were the best hybrids for grain yield with 13.30 and 9.02 ton/ha, respectively. According to the indices MP, GMP, STI and HARM among the studied hybrids the promising hybrids No.1 and No.1, 4 and9 were recommended for water stress condition in Mashhad regions. During periods of lower growth in hybrid and non-treated with high temperatures during pollination can cause lead to the compounds than others. The correlation results showed the positive and significant relation between potential for performance (no stress) indices MP, GMP, STI, TOL and HARM. Most significant and positive correlation between the indices was related to GMP and STI (0.99). In general, hybrids L1×k1263/1, L5×k1263/1, L10×k1263/1 and 14×k1263/1 due to the high level of tolerance can be used in breeding programs.

Aluminum toxicity is one of the most deleterious factors for plant growth in acidic soils because over 50% of the world’s potentially arable lands are acidic. In recent years, considerable research has been conducted to understand the mechanisms of Al toxicity and tolerance in plants. This paper reviews the effects of different concentration of Al on plant shoot, root physiological parameters such as length, fresh and dry weight, pigment content and antioxidant enzyme such as Catalase Ascorbate and Guaiacol peroxidase, malonyldialdehyde content. MAIZE (ZEA mays L.) seeds were sterilized and these seeds were then germinated in Petri dish. The germinated seeds were allowed to grow at 27oC in darkness, and 5 ml of test solution was added to each Petri dish on the second day. The test solution contained 0, 25, 50, 75, 100mM AlCl3. Aluminum toxicity caused reduction in growth in all treatments. The plants exposed to Al exhibited a substantial decline in growth, pigment content, activities of guaiacol peroxidase (GPX), catalase (CAT) and ascorbate peroxidase (APX) and leaf structure. Data show that 50 mM Al caused increased in MDA content.

Nickel (Ni) is one of the essential micronutrients for higher plants and its known function is being the metal component of urease. The effects of various Ni levels on urease activity in MAIZE (ZEA MAIZE L.) plants grown in two nutrient media containing urea or ammonium nitrate as two separate nitrogen sources were investigated. The experiments were performed as completely randomized blocks with three replications. Treatments included two growth media, the nitrogen of which was either urea or ammonium nitrate added at the rate of 84 mg L-1 and four Ni levels (0, 0.01, 0.05 and 0.1 mg L-1) supplied as NiSO4. Plants were grown in the nutrient solutions for six weeks. On the second, fourth and sixth week of the growth period, both the leaves and root samples were taken to determine their urease activities. At the end of the sixth week, the dry weights of both the shoots and roots were also measured. Urease activity in leaves of corn supplied with urea increased significantly with the increase in Ni supply till the end of the 6th week sampling date, however in those supplied with ammonium nitrate, urease activity increased up to the 3rd Ni level and 4th week of sampling date, but was reduced at the 4th Ni level in the 6th week. Urease activity in the roots of corn plants supplied with urea was the highest at the 2nd Ni level at the end of the 2nd week. Increase in Ni levels and date of sampling resulted in a decrease in urease activity. However, in ammonium nitrate-fed plants urease activity in the 2nd week of the sampling date increased up to the 4th Ni level and for other sampling dates the activity increased up to 2nd Ni level. Further increase in Ni supply and date of sampling resulted in a decrease in urease activity. Enzyme activity was higher in the roots than in the shoots and was also higher in plants supplied with urea, compared to those fed on ammonium nitrate. In MAIZE plants supplied with urea, the dry weights of the shoots and those of the roots were also higher.

Seven MAIZE inbred lines were crossed in a complete diallel cross design at the Seed and Plant Improvement Institute, Karaj, Iran, during the 2006 growing season. The parents and 42 F1 hybrids were grown in the research field of Islamic Azad University of Firoozabad, Firoozabad, Iran, using a Randomized Complete Block Design (RCBD) with three replications, during the 2007 growing season. The Hayman method was used for data analysis. Results indicated over-dominance gene effects for days from silking to physiological maturity, days from anthesis to physiological maturity, plant height, kernel depth, number of rows per ear and grain yield. The most appropriate strategy for the exploitation of these effects is to obtain hybrid cultivars and evaluate these characteristics in hybrid combinations. The gene effect for days from emergence to physiological maturity and number of kernels per row was complete dominance, suggesting that reciprocal recurrent selection would be effective. Ear leaf area and ear length were controlled by partial dominance, indicating that additive gene effects were more important than non-additive gene effects for controlling the inheritance of these traits. Therefore, improvement of these traits through selection of breeding materials is highly feasible. Broad-sense heritability ranged between 47.4% and 89.4% for days to physiological maturity and number of rows per ear; however, narrow-sense heritability varied between 7.3% and 50.6% for days from anthesis to physiological maturity and ear leaf area, respectively. Non-additive gene effects were predominant for controlling the majority of traits.

In order to investigate the response of grain yield, plant height and phenological traits of MAIZE hybrids (ZEA mays L. ) to planting date, a factorial experiment was carried out based on complete randomized block design with four replications during two growing seasons (2013-2014) at Moghan Research Station. Treatments consisted of two planting dates (May 1 and June 25) and five MAIZE hybrids (namely SC704 and SC720 from a late maturing group, TWC600 and SC647 from mid maturing group and SC301 from early maturing group). The results of statistical analysis showed a significant difference between years, planting dates and hybrids. The highest grain yield and plant height were related to SC704 and SC720. The results showed that the planting date on May 1 increased plant production compared to June 25. The highest average of days to physiological maturity related to planting date was May 1. SC704 and SC301 had the highest and lowest average of days to flowering and days to pollination in two different planting dates during two growing seasons (2013-2014) in Moghan region, respectively. Multiple regression analysis by stepwise method showed that in regards to days to pollination and days to physiological maturity with grain yield of MAIZE hybrids there was a significant positive association (P<0. 01) in two different planting dates (May 1 and June 25) during two growing seasons (2013-2014) in Moghan region. In conclusion, The phenological traits with grain yield can be used to select the best MAIZE hybrids for different planting dates.