الفهرس 
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Abstract
Two field experiments were earned out in the 1991/92 and 1992/
93 seasons each at one location: (i) the 1991/ 92 experiment was
conducted at the Gemmezah Research Station, Gharbiah on a clay soil;
rii) the 1992/ 93 experiment was conducted at the Bahteem Research
Station, Qualubiah, on a clay loam soil. The aim of the study was to
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evaluate different wheat genotypes grown in four seeding rates to study
the contribution of the growth and yield characters to grain yield.
A split plot design was used in four randomized complete blocks.
Seeding rates (40, 50, 60, and 70 kg fad-I) were in the main plots, and 12
wheat genotypes (Giza 155, 157, 160, 162, 163, 164, 165~Sakha 8, 69,
92; Gemmezah I; and Yecora) were in the subplots. Each subplot was
3.5 x 3.6 m. Path analysis was used to evaluate the interrelationships
among grain yield (dependent variable) and other six independent
variables (three yield components, and three photosynthetic traits) in
each of the two locations averaged over the four seeding rates.
Results could be summarized as follows:
1- Plant height of wheat plants at harvest was not significantly affected
by seeding rates. The genotypes varied markedly in plant height.
Giza 155 produced the tallest plants whereas Yecora plants were the
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shortest. No significant interaction was detected between seeding
rates and genotypes on plant height.
2- Number of days from sowing to 50% heading was significantly
affected by seeding rates in the second season (1992/93). Seeding
60 kg fad.-1 delayed heading compared with the other rates. The
earliest heading was recorded with seeding 50 kg fad.-1. The tested
genotypes markedly varied in heading date. Early heading was
observed with Yecora (in 1991/ 92) and Giza 160 (in 1992/93), and
late heading was recorded with Giza 162 (1991/ 92) and Giza 163
(in 1992/93). The interaction between seeding rates and genotypes
significantly affected heading date in 1992/93 season. The earliest
heading was achieved by Giza 155, Giza 157 and Giza 160 seeded
at 40 kg fad.r l.
3- Days to maturity were significantly affected by seeding rates.
Seeding 70 kg fad.-1 significantly induced early maturity. Early
maturity was observed with Yecora, Sakha 8 and Giza ] 55 and late
maturity with Giza 162, Giza 163, Giza 164 and Giza ]65. A
significant interaction between seeding rates and genotypes was
observed in both seasons. The earliest maturity was achieved by
Yecora seeded at 40 or 60 kg fad.-I as well as Sakha 8 seeded at 50
kg fad.-1 in the first season, while in the second season, Yecora
combined with 70 kg fad.-I recorded the earliest maturity.
4- Seeding rates significantly affected flag leaf area in 1992/ 93 season
where a marked differeace in this trait was detected between 40 and
60 kg fad. -1 seeding rates. Genotypes significantly varied in flag
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leaf area. Giza 157, Giza 165, Giza 164 and Giza 163 recorded the
greatest flag leaf area. Flag leaf area was significantly affected by
seeding rates x genotypes interaction in 1992/ 93 season. Giza 165
seeded at 40 kg fad.-1 recorded the highest flag leaf area in that
season.
5- Leaf area index at anthesis was not significantly affected by seeding
rates. The tested genotypes showed significant differences in LAJ.
Giza 165, Giza 164, Giza 163 and Gemmezah 1 recorded the
highest LA!. No significant interaction was detected for seeding
rates x genotypes on LAl
6- Leaf area duration was not significantly affected by seeding rates.
Genotypes markedly differed in LAD. Giza 165 recorded the
highest LAD in 1991/ 92 season, whereas Giza 157 was the leading
genotype in 1992/ 93 season in LAD. No significant effect was
observed for the interaction between seeding rates and genotypes on
LAD.