ESTIMATiON OF HETEROSIS AND COMBINING ABILITY IN SOME BREAD vIHEAT CROSSES (T. aestivum L.)

Six wheat genotypes of diverse origin were crossed in half diallel
combinations in 200212003m 2003/2004 season1 the 15 F crosses and their six
parents were grown ¡n a field experiment at Sakha Agricultural Research station,
Agricultural Research center, Egypt, in a randomized complete block design with four
replications. The experiments aimed to study heterosis and combining abUity for
heading date, maiurity date, plant height, no. of spikes/plant, no. of grains/spike, 100-
kernel weight, spike weight, grain yield/plant, flag leaf area and ciorofel Atb.content
the results are summarized as follows.
1- Highly significant differences for most traits were obtained among the studied
genotypes (parents and crosses). General and specific combining ability mean
squares were highly significant for ail studied traits
2- The best general combiners for grain yield and one or more of its attributes were
line2 and sids while the best general combiners for earliness were line I , line2and
line 3.
3Positive heterosis effects relative to the mid-parent were found for most of the tr&ts
in the crosses 3x4, 2x5 and 1x3.
4- The gca/sca ratio revealed the importance of Non-additive genetic variance in the
inheritance of all traits, except heading date and no. of grains/spike.
5- The results of specific combining ability effects, revealed that the cross line 1 x line
4 was the top performing ¡n maturity date, plant height and grain yield! plant.