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.
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.
A half diallel set of crosses among six highly diverse barley (Hordeum
vulgare L.) genotypes were evaluated at Karahta Research Station, General
Commission of Scientific Agricultural Research (GCSAR), during 2010-2011
and 2011-2012 seasons to stud
y heterosis, potence ratio, correlations among
traits and path coefficient analysis for number of spikes per plant, number of
grains per plant, number of grains per spike, biological yield ,and grain yield
per plant. Heterosis effects for seed yield ranged from%-89.52 (T-6669×S-6303)
to%16.99 (Arabi abiad mohsan×S-6689) and from%-49.94 (L-6711×S-6689)
to %-1. 35 (Arabi abiad mohsan×S-6689) relative to mid and better parents
respectively. Potence ratio values ranged from 1.14 (number of spikes per
plant) to 3.50 (biological weight) indicating that non-additive gene action was
more important in controlling all studied traits. Correlation coefficients among
traits indicated that seed yield was positively and significantly associated with
each of number of spikes per plant (0.289), number of grains per plant (0.832),
number of grains per spike (0.587), and biological yield (0.708) traits. Path
coefficient analysis indicated that number of grains per plant trait had high
positive direct effects on grain yield.
The experiment was grown in a Randomized Complete Blocks
Design with three replications, to estimate the heterosis, degree of
dominance and the inbreeding depression of three hybrids of maize.
