الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 233 |  |  |
| | | from | 233 | | |
Abstract
Two sets offield experiments were conducted during 2017/ 2018 and 2018/2019 successive growing season at the experimental farm of Kafer El-Hamam Agriculture station, Sharkia. For five crosses; (Sids12 x Line44), (Sids12 x Line35), (Line44 x Line20),(Line44 x Shandweel 1) and(Line20 x Sakha93) under normal irrigation and water stressconditions.
5.1. First experiment: Six Populations
• The present studywas performed to estimate mean performance, heterosis, phenotypic and genotypic variances, magnitude and types of gene action, heritability and genetic advance of wheat yield and yield contributing characters and its implication in improving wheat grain yield.
5.1.1. Means performance:
• Water deficit reduced means of all six generations compared with normal irrigation for all traits except proline content.
5.1.1.1.Earliness characters and proline content
• Means data showed that the F1 means were earlier than both the parents in the crosses 1st, 2ndand 4th under irrigation and 2ndunder water stress for days to heading and in the crosses 1st, 4th and 5th under irrigation for days to maturity which was desirable in further selections.
• The segregating population(F2) means were earlier than F1 means for days to heading in the 3rd cross under both condition and for days to maturity in the crosses 1st and2ndunder irrigation and all crosses under water stress.
• The means of segregating population (BC1) were equal or earlierthan P1 in all crosses except 1stand 3rdunder normal irrigation and water stress, respectively for days to heading and 1st, 4th and 5th undernormal irrigation and 2nd, 3rd, 4th and 5thunder water stress for days to maturity.
• The means of segregating population (BC2) were equal or earlier than P2 in all crosses except 3rdunder normal irrigation and 1st and 3rd under water stress for days to heading and 1st,3rd, 4th and 5thunder normal irrigation and 1st and 4thunder water stressfor days to maturity.
• For proline content F1 means were intermediate to the parentsin the all crosses under both conditionsexcept crosses 1st and 5thunder water stress.
• The F2 means were more than F1ones in the 4th and 5thcrosses undernormal irrigation and 1st and 2nd crosses under water stress.
• All the wheat genotypes when subjected to water stresshad increasing in proline contentwhen compared with the same crosses under normal irrigation.
5.1.1.1.2. Yield and its attributes
• For plant height (PH), the F1 means is taller than P1 in crosses 1st, 2nd, 3rd and 4thunder normal irrigation andwater stress.The BC2 means were more than P1, P2, F1 and F2 in the crosses 2ndand 4th under normal irrigation and3rd and 4th under water stress. For spike length (S L), the F1 means is taller than P1 in crosses 3rd and 4thunder normal irrigation and4th under water stress.The BC2 means were more than P1, P2, F1 and F2 in the crosses 3rd and 4th under normal irrigation and3rd and5th under water stress.
• For number of spikes per plant (NS/P), the F1, F2 and BC1 means were higher than P1 in 1st, 2nd and 3rd crosses under normal irrigation and 1st, 2ndand 3rdcrosses under water stress.The reduction percentages for NS/P were 8.9, 10.9, 10.4, 9.3 and 11.4% in crosses 1st, 2nd, 3rd, 4th and 5th, respectively compared with normal irrigation.
• Number of grains per spike (NG/S) in F1 was higher than P1, P2 and F2 in 3rd and 1stcrosses under irrigation and water stress. The BC2 was more than both the parents in 2nd cross under irrigation and water stress. The reduction percentages for NG/S were 12.9, 9.0, 8.2, 4.5 and 2.2% in the five crosses respectively compared with normal irrigation.
• The means for 1000- grain weight(TGW) tended to decrease under drought stress. Thus, decrease percentages were 7.92, 5.69, 15.82, 6.03 and 4.90% in the five crosses. The BC1 means were more than P1 in all crosses except 1st and 2nd crosses under irrigation, as well as the BC2 means were slightly higher than P2in all crosses except 3rd cross under irrigation.
• Grain yield per plant (GY/P) in F1was more than the best parent in the 4th cross under irrigation and 1st, 4th and 5th crosses under water stress. The F2 means were more than P1 in the 1st and 4thcrosses under normal irrigation and 3rd cross under water stress.The BC1 means were more than both parents in all crosses except the 4th cross under irrigation. The BC2 means were more than P2 in all crosses under both condition and F1 in the 1st, 4th and 5th crosses under irrigation and 2nd, 3rd and4th crosses under water stress.The reducing percentages were 23.91, 32.38, 17.98, 24.88 and 17.43% in the five crosses.
5.1.2. Heterosis
5.1.2.1.Earliness characters and proline content
• Highest relative heterosis for days to heading was seen by the 4th cross under irrigation and water stress followed by 2nd cross then 5thcross. Highest better parent heterosis is shown by the 2nd cross under irrigation and water stress.
• For days to maturity, highest relative heterosisand heterobeltosis is shown by the4th cross followed by the 1st crossunder irrigation
• For proline content, under both treatments the 2nd and 5thcrosses showed the highest positive significant heterosis and heterobeltosis except 2nd cross under water stress relative better parent.
5.1.2.2. Yield and its attributes
• The highest positive heterosis for spike lengthis shownby the 2nd followed by 3rd crosses under normal irrigation and the 1st cross under water stress.
• Positive significant relative heterosis was revealed for number of spikes per plant (NS/P) in the 2nd cross under irrigation and water stress.
• For number of grains per spike (NG/S),the 3rd cross under normal irrigation and 1st cross under water stress showed significant positive heterosis of mid-parents and better parent.
• The 2ndand 3rdcrossesunder normal irrigation and 4th and 5th crosses under water stress had positive significant relative heterosis for 1000-grain weight,while the crosses 3rd and 5thshowed positive significant relative heterobeltosis under water stress.
• The 4thcross showed positive significant relative heterosisand heterobeltosis under both conditions for grain yield per plant, as well as crosses 1st and 5th under water stress.
5.1.3. Phenotypic, genotypic and environmental variances
5.1.3. 1. Earliness characters
• The total genetic variances for days to heading, days to maturity and proline content were higher than the environmental ones in all crosses under irrigation and water stress.
• High estimates of the genetic variance were recorded for days to heading in 3rd and 5th crosses under normal irrigation and under water stress in 4th and 1st crosses.
• For days to maturity, high genotypic variances were recorded in 2nd and 4th crosses under normal irrigation and 1st and 4th crosses under water stress.
• For proline content,high genotypic variances were recorded in 5th and 2nd crosses under normal irrigation and 3rd and 2nd crosses under water stress.
5.1.3. 2. Yield and its attributes