arents (P1&P2), F1, F2 and first generation of backcrosses (BC1&BC2) of two bread wheat crosses i.e., Sids 12 x Gemmeiza 11 (C1) and Misr 2 x Sids 1 (C2), were grown in two experiments {normal sowing date 20 th Nov. (N) and late sowing date 20 th Dec.

Field experiments were conducted at Shandaweel Agric. Res. Station, Sohag, Egypt, during the two growing seasons 2018/2019 and 2019/2020 to study the effect of six irrigation regimes, i.e. I1 (irrigation at tillering and elongation stage), I2 (irrigation at tillering and flowering stage), I3 (irrigation at tillering, elongation and flowering stage), I4 (irrigation at tillering, booting and grain filling stage), I5 (irrigation at tillering, elongation, booting and flowering stage) and I6 (irrigation at tillering, elongation, booting, flowering and grain filling stage) on some agronomic and physiological traits of four wheat cultivars, i.e.Shandaweel1, Sids 14, Sohag 4 and Sohag 5. Results showed that decreasing number of irrigations and amount of applied water at different growth stages significantly decreased all studied traits. The highest reduction was recorded under I1 (1432 m-3 ha-1) for all studied traits, except days to heading and number of spikes m-2. Meanwhile, the lowest reduction was observed under I5 (3088 m-3 ha-1) for all studied traits as compared to I6 (3965 m-3 ha-1 of applied water). Irrigation at both booting and flowering are essential to reduce loss in grain yield. Moreover, Sids 14 exhibited lower yield reduction under different irrigation regimes, while sohag 4 and Sohag 5 exhibited the highest yield reduction. Therefore, Sids 14 proved to be drought tolerant cultivar, while Sohag 4 and Sohag 5 were drought sensitive. Planting Sids 14 cultivar with irrigation at tillering, booting, grain filling stages (I4) are useful to save about (36.97%) of applied water without significant decrease in grain yield.

The current study was conducted at Shandaweel Agric. Res. Stat., Agric. Res. Center, Egypt. Eighteen bread wheat genotypes were grown under four treatments during 2018/19 and 2019/20 seasons. The treatments were (1) normal conditions (sowing on 25 th November and 5 irrigations). (2) Terminal water stress conditions (sowing on 25 th November and 3 irrigations). (3) Terminal heat stress conditions (sowing on 25 th December and 4 irrigations). (4) Combined stresses (sowing on 25 th December and 3 irrigations). The combined analysis of variance showed significant differences between the genotypes, treatment, seasons for all the studied traits. The mean performance of the genotypes showed that L11 was the highest grain yield and grain filling rate under normal, water stress, heat stress, combined stresses as well as overall treatments. Genotype by genotypeenvironment biplot (GGE biplot) illustrated that the best performing genotype under normal conditions was Baj 1 while Shandaweel 1 was the best performing genotype under stress combinations. Genotype x trait biplot (GT biplot) showed a positive correlation between all the traits except, days to heading and days to maturity. Genotype by yield*trait biplot (GY*T biplot) was constructed to estimate superiority and stability for the genotypes. GY*T biplot showed a positive correlation between all yield*trait combinations. Based on superiority index (SI), the best performing genotypes was L11 (SI = 1.830) and the worst was L7 (SI = 1.935). L11 genotype can be utilized in breeding program as a source for abiotic stresses tolerance or can be evaluated in preliminary yield trials at the national level.