The experiment was carried out at the Field Crops Research Station, College of Agricultural Engineering Sciences - University of Baghdad in Jadiriyah, with the aim of evaluating the performance of partial diallel hybrids and inbred lines of maize and estimating general combining ability(GCA), specific combining ability (SCA) and some genetic parameters. The experiment was carried out in two seasons, spring and fall 2020. Eight inbred lines of maize were used in the study (BI9/834, BSW18, LW/5 L8/844, ZA17W194, Z117W, ZI17W9, ZI7W4), numbered (1,2,3,4,5,6,7,8), It was sowed in the spring season and entered into a cross-program according to a partial diallel crossing system to obtain twelve partially cross-hybrids, and it was compared with its eight parents in a comparison experiment in the fall season using a Randomized Complete Block Design (RCBD) with split plots arrangement with three replication. The plant densities of 70 and 90 thousand plants ha-1 represented the main plots, while the partial diallel hybrids and their parents represented the secondary plots. The results of the study showed that the ratio between GCA and SCA) GCA/SCA) It was more than 1 for yield traits, ear length, number of rows and number of row grains in both low and high densities, which indicates the control of the additive genetic action on these traits. While the ratio was less than one for the traits of the ear diameter under the low density, which indicates the control of dominance genes on this trait in the mentioned density, while the trait of the number of ear grains, the ratio between the general and specific combining abilities was less than one in the high density. Inbred line 8 had the highest effect for the general ability to combine under low density, which amounted to 11.075, while inbred line 2 was superior by giving the highest effect to the general ability to combine at low density, which amounted to 17.80, followed by inbred 8.

The objective of this study to estimate the components of genetic variation, phenotypic (PCV) ,genotypic(GCV)  coefficient of variation, genetic gain and its percentage. An experiment was conducted at the field of Field Crop Dept.Coll. Agric.-Univ. Baghdad, using four crosses (FI01301 Rustico), (AntignaoHi39× Nostred), (Lo1391× Rustico) and (Rusticocangini× Rustico) which developed  from crossing of genetically different of six inbred lines for maize (Zae mays L.), introduced from Italy. Genetic parameters were estimated according to the Joint scaling test using the randomized complete block design with four replications. The components  of genetic variance; Additive and dominance of the maize grain yield and some trait, were estimated. The results showed that the values of Chi square were significant  for all the studied some traits  of all crosses, thus the simple additive – dominance model in four crosses exhibited lack of good fit  for all traits, indicates the role of non-allelic interaction. Dominance gene action was higher than additive for most traits. Therefore the hybridization would be more effective than population selection to improve these traits for these crosses.

Tension caused by a lack of water (water stress or drought stress) represents the continuous and continuous threat to the survival of the plant, as many of the plants in which phenotypic or physiological modification takes place may not be able to continue and remain in the environment in which they live due to the water stress on it or the low soil moisture content. This of course is related to the prevailing weather conditions (lack of rain, high temperature, increased wind speed, low relative humidity in the atmosphere … etc.), so dry soil is defined as the shortage of soil water needed to the extent that its readiness for the plant decreases (that is, the threshold at which the plant cannot absorb Or drain the water at a speed that meets its requirements for vital activities, and photosynthesis that meets the requirements of evapotranspiration does not occur. Conversely, water tightening may be the result of increased water. An example of stretching as a result of increased water is flooding, which results in suffocation resulting from Reduced concentration of oxygen-prepared oxygen to the roots, which in turn will impair breathing. In general, tension due to a lack of water is the most common, which led specialists to call it “water deficit stress.” Because water tension occurs in natural environments as a result of rain entrapping, Such conditions are known as drought conditions and therefore drought stress is terme In laboratory conditions, water stress conditions can be achieved through the loss of water by transpiration from the leaves, a circumstance that is due to what is termed as a desiccation stress. That is, in the sense that water stress is one of the components of salt tension and osmotic tension, and in order to unify these differences according to the concept of water tension, it termed the concept of low water potential.

Correlation and path coefficient analysis were worked out for ten morphological traits in 30 three-way crosses of maize. Phenotypic and genotypic correlation analysis indicated that ear length; row numbers per ear, grain numbers per row, leaf area and leaves numbers had a positive significant correlation with grain yield per plant. Further partitioning of correlation coefficients into direct and indirect effects showed that traits days to silking, row numbers per row and leaves numbers had a positive direct effect on grain yield per plant. The traits ear length, grain numbers per row and leaf area had a maximum total effect on grain yield. Furthermore, PCA analysis has gave interested results and it supported the results of correlation and path analysis. The correlation and path analysis obviously indicated that direct selection based on these attributes may be useful in raising grain yield in maize.

The objective of present study was to compare of several methods for estimating the degree of heritability and calculating the number of genes using generation mean analysis of maize (Zea mays L.). The experiment was conducted at the field of Field Crop Dept. College of Agric / Univ. of Baghdad, for many seasons, spring and fall seasons 2009, 2010, spring 2011 and fall 2013.Six diverse inbred lines were crossed to produce F1,F2,BC1 and BC2 for four superior crosses.Broad-sense and narrow sense heritability estimates based on variance of different generations. The results showed that the four formulas used to estimate the heritability were different in estimating the values of heritability of different traits, as well as the different crosses used in the study. The broad sense heritability was differed according to the components of the formulas used to estimate. The number of genes that controlled the trait differed according to the different method of estimation and according to the studied trait, and to the all crosses. The highest number of genes (for all formulas) for plant yield, ranging from 15.85 (cross 4) to 155.7 (cross 2), because the yield is complex quantitative trait of several components, so the number of genes they control are the sum of genes that control the components. The inbreeding depression differed according to the parents involved in the crosses, and according to the studied trait, the inbreeding depression ranged from -7 for number of branches/tassel of cross 1 and leaf area of cross 3 to 68 for grain yield of cross 2. We can conclude that the best formula to estimate heritability depends on experimental design and methods of breeding.