HALF diallel set of orosses involving five parental lines were
used to estimate the type and relative amount of generic variance
components for grain yield per plant, number of spikes per plant,
1000-kernel weight, protein percentage, and fermentation time.
Genotype mean squares for all traits studied were highly signifi
cant. Additive type of gene action was found to reach the level of sig
nificnace in most cases. Dominance gene effect was larger. in magni
tude than the additive ones and appeared to be the more prevailing for
all the studied traits. High to moderate estimates for heritablity in the
broad sense were accompanied by moderate to low for the narrow
ones were detected for most traits.
Studies on the nature and degree of dominance revealed the exis
tance of over dominance for all the traits except protein percentage
where partial dominance was obtained. The negative and positive al
leles were equally distributed among the parental population in all
cases. The correlation between pareital performances and their order
of dominance revealed that low grain yield and l.000-kearlsl weight,
and few number of spikes per plant behaved as dominant traits. No
particular trend could be detected for the other two traits.
The new Egyptian policy of wheat production is to increase the area cultivated
by durum wheat in Upper Egypt because of its high tolerance to the prevalent