_____________________________________________________________________________________________________ *Corresponding author: Email: ibrahim.fathi@agr.svu.edu.eg; Asian Journal of Research and Review in Agriculture 2(1): 35-51, 2020; Article no.AJRRA.234 Heterosis and Combining Ability under Favorable and Salinity Stress in Egyptian Bread Wheat Abdelsabour G. A. Khaled 1 , Tharwat M. Elameen 2 and Ibrahim F. O. Elshazly 2* 1 Department of Genetics, Faculty of Agriculture, Sohag University, Sohag, Egypt. 2 Department of Genetics, Faculty of Agriculture, South Valley University, Qena, 83523, Egypt. Authors’ contributions This work was carried out in collaboration among all authors. All authors read and approved the final manuscript. Received 18 May 2020 Accepted 24 July 2020 Published 30 July 2020 ABSTRACT Generation mean analysis for effect of salinity soil and water was carried out to study days to 50% Tipping, spike length and No. of spikelets/spike. The results indicated that the mean squares of all genotypes were highly significant for three studied traits, reflecting a great wide genetic variability among them. The mean sum of squares due to the general combining ability (GCA) and specific combining ability (SCA) were high significant for days to 50% Tipping and No. of spikelets/spike, but specific combining ability (SCA) was significant for spike length under salinity stress. Heterosis of all crosses over mid parents (H M.P %) and better parent (H B.P %) for days to 50% Tipping, spike length and No. of spikelets/spike were estimated on this study. The most types of general combining ability effect (gi) and specific combining ability effects (Sij) are involved in the inheritance for three traits. Also, data showed that magnitudes of the non-additive genetic variance (σ 2 D), which were higher than those of additive (σ 2 A) ones for days to 50% Tipping and No. of spikelets/spike. The results exhibited that the values of heritability in broad senses (h 2 b.s%) and narrow senses (h 2 n.s%) were highly for spike length under Favorable, salinity stress and combined data with values of (87.35 and 58.42%) and (85.32 and 72.73%) and (75.70 and 12.83%). Moreover, the values of (h 2 b.s%) were highly but the values of (h 2 n.s%) were low for days to 50% Tipping and No. of spikelets/spike under Favorable and salinity stress conditions, respectively. Finally, it could be concluded that the non- additive gene action played a major role in controlling of traits of days to 50% Tipping and No. of spikelets/spike. However, the additive gene action played a major role in controlling of spike length, respectively. Keywords: Combining ability; gene action; heritability; heterosis; salinity; wheat. 1. INTRODUCTION Bread wheat (Triticum aestivum L.) is a moderately saline tolerant crop [1]. Saline stresses are the major environment that great affect the plant productivity [2]. There was a progressive and significant increase in salt soil values as the salinity of irrigation water increases Original Research Article