The aim of this study was to analyze the genetic system of drought
susceptibility index (S) foc yield and some of its components of eight parents and their
28 F1 hybnds of common wheat at two locations Two experiments were conducted in
each location. The first experiment (stress) was irrigated one time, and the second
experiment (non.stress) four times, after planting irrigation.
Significant genotypes mean squares were detected for all the studied traits
in both locations as well as the combined analysis. Locations mean squares were
insignificant for alt the studied traits, Also, significant genotypes x locations interaction
mean squares were obtained for the studied traits except parents vs. hybrids x
locations for number of spikes per plant and straw yield per plant. The parental
cuttivars Sham 6 and Sakha 8 seemed to be the best parents in drought susceptibility
index of grain yield per plant, straw yield and 1000-kernel weight, number of spikes
per plant and total plant weight.
The variances associated with general and specific combining ability (GCA and
SCA). were highly significant for all cases. High GCAISCA ratios that largely
exceeded the unity were obtained for total plant weight m both locations as well as
the combined analy&s. Low GCAISCA ratios less than unity were detected for other
cases. The interactions between locations and both types of combining ability were
highly significant for all traits, indicating that the magnitude of all types of gene action,
varied from one location to another. The parental cultivar Sham 6 (pi) seemed to be
the best general combiner in drought susceptibility index for number of spikes per
plant and 1 000-kernel weight and gave significantly negative gca effects for drought
susceptibility index in total plant weight and grain yield per plant in both locations as
well as the combined analysis. The desirable SCA values were recorded by the four
crosses (1 x 6). (2 x 7) ,(3 x 5) and (4 x 8) for number of spikes per plant, cross (5 x
7) for number of kernels/spike, the two crosses (1 x 4) and (3 x 4) for 1000-kernel
weight, the two crosses (2 x 3) and (5 x 8) for grain yield (3 x7) crosses for total
plant weight and (1 x 7) for straw yield /plant.
Keywords: Drought susceptibility index, Yield components, Wheat, Diallel cross.