DROUGHT stress is the primary restricting factor of crop productivity in Egypt. The development of drought-tolerant lines is urgent. However, drought tolerance is a complex trait. So, this work aimed to reveal the genetic background and gene effects controlling of yield parameters and to discover the epistasis in two bread wheat crosses; Sakha 93 × pureline 5 and Gemmeiza 10 × pureline 42 under irrigated and drought conditions, utilizing seven generations viz. P1, P2, F1, BC1, BC2, F2 and F3.
Genetic analysis revealed that additive and dominance effects are involved in the genetics for most traits in both crosses and conditions. Both additive x additive and additive x dominance effects were significant in most cases, supporting the presence of duplicate type of epistasis. Therefore, early generation selection would have failed.
F1 hybrids (Drought susceptibility indexes were 0.278 in cross I and 0.295 in cross II), were less affected by drought stress conditions, displaying the presence of heterobeltiosis for drought tolerance. Broad-sense and narrow-sense heritabilities and genetic advance ranged from moderate to high for most of the studied traits and these two crosses could be selected to produce high yielding lines under drought conditions.