This study was carried out at the Experimental Farm, Fac. of Environ. Agric. Sci., El Arish, Suez Canal
Univ., Egypt, during three successive summer seasons (2009 to 2011). Seven elongated eggplant fruit lines were used in
7x7 half- diallel cross mating design to produce 21F1 hybrids. In the two successive summer seasons of 2010 and 2011,
all 28 genotypes were evaluated in a field experiment with check hybrid "Snow F1". A randomized complete block
design with three replicates was used in the two seasons of 2010 and 2011 to estimate heterosis relative to mid parents,
better parent and check hybrid, also dominance type and its relation to combining ability variances were determine for
some plant and fruit characters. The obtained results showed high significant differences among the parental lines and
their 21F1hybrids for all studied traits. Heterosis over mid-parents, better parent and check hybrid were recorded in 14,
8 and 4 ones for total fruit yield/plant, respectively. However, heterosis over mid-parents and check hybrid were
reflected by 5 and 4 crosses for number of branches, 5 and 12 ones for number of fruits/cluster, 10 and 15 ones for
percent of fruit clusters/plant and 8 and 11 ones for total fruit number /plant, respectively. However, no heterosis was
detected for average fruit weight, fruit length and diameter. Determination of dominance type and GCA and SCA
variances showed that additive gene action play the main role in the inheritance of all studied traits, except total
yield/plant trait. The non-additive gene action was predominance and more important in the inheritance of total
yield/plant.