الفهرس 
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Abstract
Heterosis and combining ability in grain sorghum [ Sorghum bicolor
(L.) Moench] under optimum and low level of nitrogen.
The experiment was conducted in two seasons 2006, 2007 in
Shandaweel Agric. Res. Station, Sohag. This experiment included the
thirty-two crosses and their parental lines (four B and eight R lines) plus
the check hybrid Shandaweel-2.
In this study the RCBD design were used in the experiment for the
each nitrogen levels (100 and 50 kg N/fed.,) to evaluate the genotypes.
Line x tester analysis were used to compute the genetic parameters.
The obtained data in the experiment were illustrated as following:-
I-Mean performance:-
The combined analysis of variance over nitrogen levels at each
season showed highly significant differences between genotypes and
nitrogens for all studied traits. Also, significant or highly significant
differences between seasons for days to 50% flowering, plant height,
panicle length and 1000 grain weight .The interactions between
genotypes x seasons was highly significant for all studied traits. The
interactions between genotypes x nitrogens was highly significant for all
studied traits except for both panicle width and no. of green leaves the
interaction was insignificant. While, the interactions between seasons x
nitrogens was insignificant for all studied traits except for plant height,
panicle length and grain yield/ plant, also, the interactions between
genotypes x nitrogen x seasons were highly significant for days to 50%
flowering, plant height, panicle length, 1000 grain weight and grain
yield/plant.
1- The combined data over two seasons indicate that days to 50%
flowering for the female lines under 50 kg N level ranged from69.83(SPDM-94021-B) to 75.50 (SPAN-94037-B), while for the Rlines
it ranged from 73.17 (ICSR-89036) to 78.33 (ICSR-90012).
Moreover, for the crosses it ranged from 64.00 (SPAN-94037-A x
ICSR-89028) to 77.33 (SPAN-94037-A x ICSR-90012). Also, for
the female lines under 100 kg N level it ranged from 65.00 (SPDM-
94021-B) to 70.50 (SPAN-94037-B), while for the R-lines it ranged
from 68.83 (ICSR-89036) to 73.00 (ICSR-90012). While, for the
crosses it ranged from 59.67 (SPAN-94037-A x ICSR-94007) to
70.00 (SPAN-94037-A x ICSR-90012). The results indicated that
the increase in the average of days to 50% flowering for the female,
male lines and crosses under 50 kg N level was 5.33, 4.92 and 5.88
days, respectively. It can be concluded that the average of days to
50% flowering for all studied genotypes increase under low
nitrogen, which means that low nitrogen delays days to 50%
flowering.
2- Plant height for the female lines over two seasons under 50 kg N level
ranged from 123.33 (SPDM-94021-B) to 178.33 (SPAN-94037-B),
while for the male lines it ranged from 110.00 (ICSR-94007) to
204.17 (ICSV-273). Moreover, for the crosses it ranged from 155.83
(SPDM-94021-A x ICSR-89028) to 223.33 (SPST-94009-A x
ICSV-273). Under 100 kg N level for the female lines it ranged from
134.17 (SPDM-94021-B) to 199.17 (SPAN-94037-B), while for the
R-lines it ranged from 116.67 (ICSR-94007) to 217.50 (ICSV-273).
While, plant height for the crosses ranged from 170.00 (SPDM-
94021-A x ZSV-14) to 279.17 (SPAN-94037-Ax ICSV-273). The
average of crosses was significantly higher than those of the female
and male lines at each and over two seasons under the two nitrogen
levels indicating the heterotic effect. whereas, the male line ICSV-
273 gave the tallest plant height of its crosses