Abstract
To determine the genetic control of seed yield and yield-related traits by using Hayman's approach, and to estimate the proportion of dominant and recessive genes controlling traits in each parent, five genetically divergent genotypes of sunflower (Helianthus annuus L.) were crossed using a half-diallel mating design (excluding reciprocal crosses). The parents along with their half-diallel crosses were evaluated using a randomized complete block design with three replicates at Kafr El-Hamam/Sharkia and Al-Arish/North Sinai Agricultural Research Stations, Agricultural Research Center, Egypt. Significant differences were observed among genotypes for all studied traits at individual locations and across locations. Magnitude of additive gene effects was larger than that for dominance effects for all studied traits (except for seed weight plant
−1
) when the ratio [(a/b) & (H
1
/D)
0.5
] was greater than unity at both locations, as also confirmed by high narrow-sense heritability. Hence, selection in early generations would be effective at both locations for these traits. Parents L1031, L1033, and Miak were desirable for early flowering and maturity as well as for short stature and increased proportion of seed oil, whereas Giza 102 and L24 were promising parents for improving number of green leaves plant
−1
, head diameter, 100-seed weight, and hence seed weight plant
−1
.