Nine inbred lines of yellow maize were mated to three testers in 2001
growing season . Parents and their top-crosses were evaluated at Sakha, Sids and
Nubaria locations in 2002 growing season. Combining ability analysis was calculated
by the line x tester analysis according to Kempthorne (1957). Mean squares due to location (Loc), genotypes (G), parents (P), crossess (C)
and (P vs C) and their interactions with locations were significant for all studied traits
excep~ (G x Loc) , (P x Loc.) and (C x Loc)were not significant for all studied traits
except grain yield (ard/fad). Also mean squares of crosses and their partitions ( L), (T)
and ( txT) were significant for all traits except (T) for ear diameter and ( L x T) for
plant ~nd ear height and ear diameter. The best inbred lines had desirable significant GCA effect for grain yield were
SK-70 O,SK-7078/2 and SK-7078/1. Eight single crosses as top-crosses produced more grain yield than checks
single cross 155 (23.8 ard/fad) , among them three crosses. i.e. SK-7070 x L 121
(31.3 ~rd/fad), SK-7078 x L 121 (27.1 ard/fad) and SK-7017/4 x L 121 (25.8 ard/fad)
had si~nificant by more yield than check SC155, Also, six three way crosses as top-
crosses yielded more than the check TWC 352 (20.8 ard/fad) from these crosses
two crosses, SC SK-22 x SK-7070 (26.1 ard/fad and SC SK-22 x SK-7078/30 (23.99
ard/fa~) produced significantly by more than the check TWC352. ~ hese materials can be used to improve yellow maize and are very useful in
maize breeding program. I he inbred lines SK-7017/4, SK-7017/10 and 7017/2-4 exhibited the highest
positive significant GCA effects for resistance to downy mildew disease. These inbred
lines could be used in breeding program. The top-crosses line 121 x SK-7078/1 and
SC SK-21 x Gm-1004 had significantly positive SCA effects for resistance to downy
milde-.y disease. However GCAISCA ratio was less than unity (0.21) for resistance to downy
mildew disease, indicating that a non-additive effect was more important in
inheritance of this trait.