This investigation was carried out at Giza Experimental Station, Agricultural
Research Center, during the three successive seasons (2003 - 2005) to study the
heterosis, genetic parameters, heritability in broad and narrow sense and genetic
advance for yield, its components and earliness in an Egyptian cotton cross of Giza
85 x Giza 90. Results show that the F1 exceeded the higher parent for all studied traits
except boll weight and position of first fruiting node. Heterosis effects relative to better
parent and mid - parents were positive and significant for seed cotton yield per plant,
lint yield per plant, boll weight, lint percentage %, seed index and number of harvested
bolls per plant. On the other hand, negative and high significant were observed for
days to first flower and days to first opening boll traits. While position of first fruiting
node and earliness % recorded highly significant negative heterotic effects relative to
better parent. The inbreeding depression values were significant and negative for
seed cotton yield per plant and days to first opening bolls. Potence ratio, over
dominance values were obtained for most traits except for boll weight, position of first
fruiting node and earliness % that showed partial dominance. Significant and positive
additive gene effects were found for position of first fruiting node, days to first flower
and days to first opening bolls, while it was negative significant for the other
characters except seed index. Dominance gene effect was positive and significant for
lint percentage %. The non-additive components were greater in magnitude than additive
component for most traits. Additive x additive type of epistasis values was significant
and highly significant for all studied characters except seed index, position of first
fruiting node and days to first flower. High values for broad sense heritability were
detected for seed cotton yield per plant, lint yield per plant, days to first opening bolls,
number of harvested bolls per plant and earliness %, but moderate values for broad
sense heritability were detected for the other traits. Moderate narrow sense heritability
values were recorded for the most traits. The expected genetic advance values for selecting the higher 5% of F2
population were 18.70, 17.73, 16.28 and 14.77 % for number of harvested bolls per
plant, lint yield per plant, boll weight and seed cotton yield per plant, respectively. It could be concluded that the improvement of position of first fruiting node
position of first fruiting node could be achieved in early segregating generations, but
other characters needs intensive selection through later generations.