In this investigation six parental varieties of squash obtained form different
sources were used. These varieties were : Eskandrani (P,). Giado (P2). Zucchino
rnezza lung bianco (P3). Zucchino 544-005 (P4). White bush scallop (Ps) and Zucchino
nano verda di Milano (Ps).These parental varieties were crossed among them to
obtain 15 F, hybrids through diallel crosses mating design excluding reciprocals. All
genotypes which included the six parental varieties and their 15 F, hybrids were
evaluated. Different yield and yield component traits as well as the nature of         resistance for powdery mildew were studied.                                                               . The results indicated the presence of highly significance differences among
genotypes. This finding was expected. where the parental varieties were obtained
from different sources. The results also revealed that no parental variety exceeded the
other parents for mean performances for all studied traits. The parent P3 was the
earliest and gave the highest yield. In the same time. the Ps and Ps were the highest
for some traits. The F, hybrid P3XPS was the earliest hybrid. while the F, hybrid P4XP_S was
the latest. PsxPs was the lowest hybrid for F.Y.lP. and No. F.lP. The highest F, hybrid
was P2XP₄ for No. F.lP. Psxf's showed the high level of resistance for powdery mildew. Heterosis values were observed for most hybrids. The best heterosis
(HMP%)values were: -19.72(P₃ x Ps): -26.65(P, x P₂): -9.55(P, x Pe): 111.43(P₄ x Ps):
20.62(P₄ x Pe): 76.05(P, x Ps): 20.63(P₄ x P_s): 34.28(P_s x P_s) and 800.3(P, x Ps) for
D.1S! F.F. No.1S! F.F.N .. 1^S! P.D .. F.Y.lP kg .. WF/P.g .. NO.F.lP .. F.L.cm .. F.D.cm. and
D.S .. estimated from the mid-parents. respectively. The results also cleared that both additive and non-additive genetic variances
including dominance could not be neglected in the inheritance of all studied traits of
squash.