الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Mean squares of net energy lactation for the evaluated maize population during 2012 summer season presented in (Table42). Population varied significantly (p 0.01) regarding net energy lactation. Orthogonal comparisons illustrated significant difference (p 0.01) between the improved synthetics and the base population. Also, the improved populations (selections)deviated significantly (p 0.01) from the studied check varieties. Furthermore, the interaction between populations and the plant densities was significant (p 0.01). In the meantime, the effect of plant densities was not significant. Mean net energy lactation and the realized gain from the two studied scheme of selection presented in (Table 46). Under low density, the highest significant value of net energy lactation was that of S1-family selection synthetic (14.620Mcal/kg). The latter mean was significantly similar to the value obtained from SC 173 check variety (14.505Mcal/kg). The second significant value of net energy lactation were that resulted from the improved synthetic by half-sib family selection (14.190Mcal/kg).Significantly lower values of net energy lactation showed by either the base population or the check TWC311 (13.625 or 14.025Mcal/kg, respectively). The realized gain in net energy lactation due to S1-family selection scheme reached 7.30% over the mean of the base population or 3.48% over the average of the studied check varieties. In the meantime, significantly lower magnitude or realized gain in value of net energy lactation due to half-sib family selection scheme reached 4.15% relative to the base population or 0.439% relative to the average of the check varieties had anticipated Under high plant density (30000 plant/faddan), the highest significant value of net energy lactation was that of S1 family selection synthetic (15.190Mcal/kg). The second significant rank in value of net energy lactation expressed by half-sib family selection synthetic (14.880Mcal/kg). Significantly lower values of net energy lactation showed by either the base population or the check TWC 311, SC 173 and TWC 329, (13.990,13.550 and 13.210 Mcal/kg, respectively). The realized gain in value of net energy lactation due to S1 family selection scheme reached 8.58% over the mean of the base population or 11.83% over the average of the studied check varieties. In the meantime, significantly lower magnitude of realized gain in value of net energy lactation due to half-sib family selection scheme reached 6.36% relative to the base population or 9.55% relative to the average of the check varieties had anticipated. Walejko and Russel (1977), evaluated recurrent specific combining ability in two open- pollinated maize cultivars ,i.e. , ”kolkmerier” and ” Lancaster”. They concluded that, the recurrent selection program had been successful in increasing frequence of genes with favorable yield effects in crosses , and over- dominance was relatively unimportant in the changes in yield potential of the two cultivars.