INHERITANCE OF ADULT PLANT RESISTANCE TO LEAF RUST IN FOUR EGYPTIAN WHEAT CULTIVARS AND THEIR CROSSES WITH FOUR LEAF RUST RESISTANCE MONOGENIC LINES.

Leaf rust monogenic lines i.e. Lr27, Lr29 were crossed with four Egyptian wheat cultivars (Triticum aestivum L.,) also, Lr46 was crossed with 3 wheat cultivars and Lr2a was crossed with one cultivar (Sakha 93). These parents, F1's and F2's were tested at adult plant stage under field conditions against race mixtures of the pathogen (Puccinia triticina Eriks.) under the stress of artificial infection. The parents of monogenic lines Lr2a, Lr46, Lr29 and Lr27 showed low disease severity. While, Gemmeiza 7, Sakha 61, Sakha 93 and Sids 1, showed high disease severity against leaf rust disease. The F1's tested plants showed low disease severity with most of crosses except three crosses i.e. Lr27 + Sakha 61, Lr27 + Sakha 93 and Lr27 + Sids 1, which showed high disease severity. The F2 plants populations were segregated into two gene pairs. The dominance tend to the direction of low disease severity (partial leaf rust resistance) with eight crosses. However, the dominance tend to the side of high disease severity with three crosses that were previously mentioned with F1's. But no segregates was recorded with the cross Lr2a + Sakha 93 and dominance tend to the aside of low disease severity (partial leaf rust resistance). The cultivar Sakha 93 exhibited the adult plant resistance to the gene Lr2a under field conditions. These findings may prove that this gene is an effective under the Egyptian environmental conditions. The partial leaf rust resistance in the tested wheat cultivars was thought to be controlled by digenic pairs in adult plant stage. The selection for partial leaf rust resistant materials in the early generations was possible but delaying it to late ones is more effective, due to the important role of dominance effect in the expression of the character.