This investigation aimed to evaluate some three-way crosses of Egyptian
cotton for combining ability and further partition of genotypic variance to its
components for yield and yield components. The genetic materials used in the present
study included six cotton varieties and their 60 three-way crosses. These genotypes
were evaluated during two successive growing seasons at Sakha Agricultural
Research Station, Kafr EI-Sheikh Governorate for the following traits: seed cotton
yield/plant, lint yield/plant, boll weight, number of open bolls/plant, lint percentage,
seed index and lint index. The results revealed that partition of the three-way crosses mean squares to
its components predicted the significant contribution of additive, dominance and
epistatic variances in the genetic expression of yield and its components. Giza 86
and Giza 89 varieties were t he best general combiners a sap arent a ndlor grand
parent in the three-way crosses for yield and yield components. Therefore, these
parental varieties could be utilized in a breeding program for improving these traits to
pass favorable genes for improving hybrid and subsequently producing improved
genotypes through the selection in segregating generations. The best combinations
as grand parents (parent's of single cross) were a result of crossing poor x poor
and/or good x poor general combiners in most of stuc!ied traits. Thus, it is not
necessary that parents having high general combining ability effect (gk) would also
contribute to ,igh speciflc combining ability effects (dij).The combinations [(Giza 76 x
Giza 87) x Giza 85, (Giza 76 x Giza 77) x Giza 89, (Giza 86 x Giza 89) x Giza 85,
(Giza 86 x Giza 76) x Giza 87, (Giza.86 x Giza 77) x Giza 85, (Giza 80 x Giza 87) x
Giza 89, (Giza 85 x Giza 77) x Giza 87, (Giza 86 x Giza 87) x Giza 77 and (Giza 89 x
Giza 87) x Giza 85J appeared to be the best promising three - way crosses for
breeding toward improving the yield traits potentiality. Most of these combinations
involved at least one of the best general combiners for yield. In addition, the results
showed that field and its components were mainly controlled by adC!itive variance as
well as additive x dominance and dominance x dominance epistatiC variances, while
the other components play the minor role in the inheritance of these traits. Thus, the
selection within the advanced generations of the previous three-way crosses may be
effective for improving yield components.