Estimation of Gene Action, Genetic Diversity And Hybrid Vigour in Lines of Maize ( Zea mays L.) Using The SSR Technology

Abstract

The cross 0f (Line x Tester) among eight pure Inbred lines of maize (5 lines) and (3 testers) at fall season of (2018) at one of Albo Thiab's fields (north of Ramadi) to produce (15 single hybrids), and compared with spring season of 2019 at the same field. The experiment included implantation of lines' and hybrids' seed produced from lines' crossing with each other that contain 23 genotypes (8 fathers + 15 hybrids) using R.C.B. design of three replications to calculate gene action controlling traits inheritance and to discover the magnitude of genetic spacing among fathers and hybrids using indicators of SSR. The results showed the following: There were significant differences among the genotypes in all studied traits, and the tester (MGW-16) and inbred line (NadH52) achieved the highest yield of plant grains mount 155.33 and 126.75 gm. respectively, this significance reflects on the hybrid (NadH52 X MGW-16) which has the highest mean of individual plant yield reached 267.38 gm. The results of the genetic analysis indicated the domination of the non-host gene action in controlling the inheritance of all studied traits except for the leaf area that was under the influence of the host act of genes. The tester (Pio-36) has the highest value for desired general combining ability for grains yield which was 0.26, while the (Zm-6) inbred line has the same one highest positive value (37.79) for the same trait, but some crosses have a desired private combining ability for several traits, most important of them is grain yield which was 44.27 for the hybrid cross (NadH26 X MGW-16). The heritability ratio in its broad sense was of high values, while the values of the same ratio in the narrow sense were low for most traits, a especially the grain yield, where the rate of heritability in the broad sense reached 86.77% and 11.66% for narrow sense. The average degree of dominance was greater than true one for all studied traits except for leaf area and this indicates that there is superior control of genes over the inheritance of studied traits. All hybrids gave the values of the heterosis in both positive and negative directions of all studied traits. The most important characteristic of which was the grain yield obtained in the hybrid (NadH26 X Pio-36) recording the highest value of the heterosis in the positive direction reached 122.13% while it was -4.93% for (NadH291 X MGW-16) cross. The results of the molecular analysis of the SSR indicators showed the success of the ten primers used to show genetic variance between parents and hybrids, as they succeeded in diagnosing 30 DNA bundles spread within the genomes of parents and their individual hybrids, 22 of which were mixed in appearance, which resulted in a high phenotype percentage to reach 73.33%, The primer ume218 was the best in the detection of genetic variants. The percentage of primer efficacy and discriminatory ability of the primer was 20% and 27. 27%, respectively. Genetic diversity values that were estimated according to the Ni and Li coefficients, indicated that the least genetic diversity ( the lowest genetic similarity) among parents was between father Zm-6 (number 5) and Sy-52 (number 7) which was 10.62, and the widest diversity (the lowest genetic similarity) among hybrids MGW – 16 x NadH291 (8 x 2) and MGW – 16 x Zm-6 (5 X 8) were it reached 13.54, According to the pattern of the genetic affinity tree using the (UPGMA) method, parents and hybrids separated into two major groups: A and B, subgroups, and sub-subgroups, where similar singles lined up next to each other in a (Cluster)