The experiment was grown in a Randomized Complete Blocks
Design with three replications during two seasons. Generations
means analysis method was used to study the genetic parameters for number of days to heading, number of days to maturity, plant
height, number of spikes per plant, number of grains per spike and grain yield per plant of two bread wheat crosses Triticum aestivum L. (Gairwel7 x Douma4), (Azaz1 x Soued), Results have shown that
both additive and dominance genetic effects were high significant in most evaluated traits, with predominance of the dominance genetic effects’ values. Also, epistatic genetic effects have contributed to inheritance of most studied traits. The signs of dominance and dominance x dominance were opposite in most examined traits indicating duplicate epistasis for all studied traits of the first cross and for number of days to maturity, plant height and number of grains per spike of the second cross, that indicates that the selection for these traits should be delayed after several generations. High phenotypic variations were composed of high genotypic variations and less of environmental variations, indicating the presence of high genetic variability for different traits and less influence of environment. Highly significant heterosis relative to mid and better parents in F1 was recorded for most characters, accompanied with inbreeding depression for all traits in
F2. Narrow sense heritability and genetic advance were low in most cases due to the dominant of non-additive genetic action in controlling the genetic variation of the most studied traits.
This study was carried out at Karahta station of field crops research
department General Commission for Scientific Agriculture Researches
(G.C.S.A.R.) Damascus Syria during the 2009 -2010 and 2010 -2011 growing
seasons to estimate gene action, p
otency ratios, heterosis and Inbreeding
depressions. Five population seeds of two single hybrids (Cham-5 × Azeghar-1),
(Bohoth-5 × Gidara-2) were formed by crossing of four inbred lines. The
crosses were subjected to randomized complete block design (RCBD) with
three replications in order to evaluate plant height (PH), number of grains per
spike (GRSP), flag leaf area (FLA), thousand kernel weight (TKY) and grain
(p<0.05) yield per plant (GYP). Mean square results showed significant
differences among mean values of the five populations for all studied traits in
all crosses. Significant heterosis values compared to mid and better parent were
observed for all traits with exception of (PH) (5.82, 1.62)%, (GRSP) (27.49
9.66)% and(TKY) (3.05 7.53)% for Cross-1. (GYP) (82.46, 96.63)% for Cross-
2. (GRSP) (9.09 5.14)%. The potency ratios exceeded (+1) in all traits and
crosses except (PH) (-2.23) for Cross-2. Indicating that over-dominance
towards low placement. The results indicated that Inbreeding depression values
were significant for all traits in Cross-1 except for (GRSP) (10.33), and (TKY)
(15.23). While its values were non- significant for all traits inCross-2except
(GRSP) (25.46*). In most traits epestasis or dominant gene action occupied the
first rank in controlling these traits in both crosses. It could be suggested that
selection for most studied traits in the subsequent generations will be relatively
more effective than in early generations.
This research was conducted at the Department of Maize in the General
Commission of Science Agriculture Research (GCSAR) Damascus, Syria. The
genetic material included parental inbred lines and the first and second (F1, F2)
generations of two hybr
ids of maize to estimate the heterosis, degree of
dominance and the inbreeding depression under two treatments of irrigation.
Results showed that mean squares of inbred lines P1, P2 and the first generation
were non significant for all studied traits, while the variance of the second
generation F2 was highly significant under the stress and non stress treatments,
The hybrid (IL.275–6×IL.362–6) showed the highest average of yield under
stress and non stress treatment, a Positive heterosis effect relative to mid
parents and the better parent was recorded for ear height, ear diameter, 100
kernels weight and yield per plant, The degree of dominance showed that the
branches per tassel was controlled by partial dominance on the other hand the
ear diameter and yield per plant showed the greatest values of inbreeding
depression, Results revealed the effective selection among the F2 individuals of
the studied hybrids specially the hybrid (IL.275–6× IL.362–6) through the late
generations (S5, S6) to get new inbred lines of maize which had dominance
desirable alleles to improve yield and it's components especially under water
stress conditions.
Six population seeds of three yellow maize hybrids were formed at Agricultural Research Center, Homs, during 2008 and 2009 growing seasons. Their plants were evaluated in 2010. The present work aims to determine the genetic parameters in six populati
ons (P1, P2, F1, F2, BC1, and BC2). Mean square results showed significant differences among mean values for all traits in all crosses. Significant heterosis values were positive and relative comparing to mid and better parent for most traits. The potence ratios exceeded (+1) in all traits and crosses except ear height, indicating thus over-dominance. In breeding, depression values were significant in most traits for Cross-1, while their values were non- significant in all traits for Cross-2 except plant height, and also in Cross-3 except plant height and grain yield per plant. In most traits epestasis or dominance gene action occupied the first rank in the genetic effects in order of importance to cross, with the exception of number of rows per ear, number of kernels per row and grain yield per plant where additive gene action occupied the first rank for Cross-2 and Cross-1 respectively. Therefore, it could be suggested that selection for most studied traits in the subsequent generations will be relatively more effective than in the early generations.
During the three successive seasons of 2002, 2003, and 2004 six populations,
viz.,P1,P2,F1,F2,BC1, and BC2 of two single crosses of cotton (Aleppo40 x
Aleppo90) and (Aleppo33/1 x Line118) were established and evaluated to
explore heterosis, inbree
ding depression, heritability and genetic advance
under selection for reproductive branches number, number of bolls per plant,
boll weight, and ginning percentage. Significant positive heterotic effects were
found for all the studied traits in two crosses except ginning percentage (in the
second cross). Significant positive heterosis over mid-parent and higher parent
for yield components (number of bolls per plant and boll weight) may lead to a
positive heterosis for seed cotton yield/plant.