GENERAL AND SPECIFIC comma ABILITIES AND THEIR lNTERACTlGNS wrm THREE NITROGEN LEVELS FOR GRAIN YIELD AND RELATED TRAITS IN BREAD WHEAT (Tritr'cum aestivum L.)

This study was carried out In 2003/2004 and W5growing seasons at
the experimental Farm. Faculty of Agriculture. Kafr El-Sheikh. Tania University
Six bread wheat cultivars. were crossed in one half diallel crosses mating
design to study combining ability and heterosis and their interactions with nitrogen
fertilizer levels (40. 60 and 80 kg leddan). Heading and maturity dates. plant height
(om). spike length (cm). number of grainsispike. spike weight (g), moo-grain weight
(g) traits were evaluated:
1. Nitrogen fertilizer levels measures were found to be highly significant for all
studied traits. The mean values were higher at the high nitrogen level than the low
level for all studied traits. Genotypes (parents and crosses). parents vs. crosses
mean squares exhibited highly significance for all studied traits under the three
nitrogen levels and the combined data.
2. The best general combiners for grain yield and one or more of its attributes were
Sakha 94. Gem. 7 and Sakha 93. while the bast general combiners for earliness
and shortness were Sakha 81 and Sakha 93.
3. General and specific combining abilities and their interactions with nitrogen
fertilizer levels were found to be highly significant for all studied traits under the
three nitrogen levels and the combined data. This finding indicated that both
additive and non-additive genetic variances were important in the inheritance of alt
studied traits.
4. The hybrid combinations (Gem. 7 x Side 1) and (Gem. 7 x Gem. 9) showed highly
significant desirable S.C.A. effects for heading date under 40. 60 kg nitrogen and
the combined data. while the crosses (Sakha 61 x Side 1) and (Sakha 93 x Gem.
7) showed highly significant desirable S.C.A. effects for maturity date under 60
and 80 kg nitrogen as well as the combined data. For grain yieldiplant the cross
(Sids 1 x Gem. 9) had significant positive specific combining ability effects under
60 kg nitrogen and the combined data.
5. The GCNSCA ratios revealed that additive gene effects were of greater
lmporhnce in the inheritance of all studied traits.
8. Eight crosses exhibited highly significant positive heterosis percentages over mid-
parents under three nitrogen levels and the combined data. while none of the
hybrids significantly out yielded its higher parent.