Two field experiments was carried out at the Experimental Farm of Faculty of Agriculture, Kafrelsheikh University -North Nile Delta, Egypt, during the two successive winter seasons of 2014/2015 and 2015/2016, to investigate the effect of different nitrogen rates (60, 120, 180 and 240 kg N/ha) and phosphorus rates (0, 36 and 72 kg P 2 O 5 /ha) on yield and yield attributes of two bread wheat cultivars (Misr 2 and Giza 168) grown on clay soil conditions. Misr 2 was higher than Giza168 in values of number of days to heading, plant height, number of fertile tillers in both seasons and number of grain /spike, biological yield, grain yield and straw yield in the first season. Giza 168 recorded the highest values for 1000 grain weight and harvest index in the first season. Fertilizing with 240 kg N/ha resulted the highest values of yield attributes and significantly exceeded other studied levels (60, 120 and 180 kg N/ha). Application of 240 kg N/ha recorded the highest values of grain and straw yields (7.430 and 6.514 t/ha) and straw (12.071 and 10.119 t/ha) in the first and second seasons, respectively. P 2 O 5 had significant effect on most characters under this study. Increases P 2 O 5 rates increased all traits except heading date and harvest index, where the inverse was true P 2 O 5 . Fertilizing with 72 kg P 2 O 5 /ha resulted the highest values of grain yield (6.564 and 6.749 t/ha) and straw yield (10.110 and 11.062 t/ha) in both seasons. Respectively. Fertilizer with 240kg N/ha and 72 kg P2O5/ha recorded the highest values for all traits in both seasons.

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The newly bread wheat cultivar Gemmeiza 11 has been selected from a local cross made at Gemmeiza Agricultural Research Station, Wheat Research Dept. FCRI, ARC. Egypt, using the pedigree method.

Gemmeiza 12, a new bread wheat variety released by Wheat Research Department, Field Crops Research Institute, ARC, Egypt in 2012, offers wheat growers a new choice for high yielding, and rust resistant variety. Gemmeiza 12 originated and selected from a hybrid made at the International Maize and Wheat Improvement Center (CIMMYT). The parentages and pedigree of Gemmeiza 12 are : OTUS/3/SARA/THB//VEE CMSS97Y00227S-5y-010M-010Y-010M-2Y-1M-0Y-OGM .Based on the results of 76 yield trials conducted during three successive growing

Half diallel set of crosses involving six durum wheat parental lines were used to estimate the type and relative amount of genetic variance components for yield and its attributes under two locations. The results revealed that additive type of gene action was found to reach the level of significance in some cases at the two locations. Dominance gene effects were larger in magnitude than the additive ones and appeared to be the more prevailing for all the studied traits under both locations. "F" value coupled with Ko/Kr showed an excess of positive and negative alleles in parents at the two locations. Studies on the nature and degree of dominance revealed the existence of over-dominance for all studied traits at the two locations. The correlation between the parental performance and the parental order of dominance were found to be negative for all studied traits studied except plant height and number of grains per ear at the two locations and for ear length and number of spikelets per ear at the second location. High estimates of heritability in the broad sense were accompanied by moderate to low estimates for the narrow sense were detected for most traits.