الفهرس 
INTRODUCTION…Only 14 pages are availabe for public view
 |  | from | 167 |  |  |
| | | from | 167 | | |
Abstract
Improving grain yield and quality under low-N has been a desirable goal of wheat breeders. This study was initiated with the objective of estimating genetical parameters in wheat crosses and using them in breeding programs under contrasting nitrogen environments, during the three successive growing seasons of 2020/21, 2021/22 and 2022/23 at the Experimental Farm of the Faculty of Agriculture, in Fayoum. University. A total of 36 genotypes comprising (6 parents, 15 F1 and F2 were grown in two separate and adjacent experiments, representing two different nitrogen fertilization levels; (low, E1) 50 and (recommended, E2) 75 kg N/fed. Each experiment was designed in a randomized complete block design (RCBD) with three replications. Combining ability, heterosis and inbreeding depression effects were estimated for physiological, yield and yield components, nitrogen efficiency, in addition to grain quality traits. The genetical analysis was conducted using Griffing (1956), Method 2, Model 1. The results revealed that, the mean squares due to nitrogen levels, genotypes and genotypes × nitrogen levels interactions were significant for all the studied traits. This indicates that, variability exists among these populations may increase the chance appearance of good new combinations that can be isolated in the succeeding generations. Mean squares of general (GCA) and specific (SCA) combining abilities were significant for all the studied traits,