YIELD STABILITY OF WHEAT UNDER SOME DROUGHT AND SOWING DATES ENVIRONMENTS IN DIFFERENT IRRIGATION SYSTEMS

Several field experiments were conducted to screen 29 bread wheat lines (Triticum aestivum L.), 5 durum wheat lines (Triticum durum L.) and 4 commercial check varieties for grain yield (ardab/fad.) under twelve diverse environments for drought and heat stress in drip and sprinkler irrigation systems of newly reclaimed sandy soils and surface flood irrigation system of old clay soils. The combined analyses of variance showed highly significant differences among environments, genotypes and environments x genotypes for all irrigation systems. Wheat genotypes had higher grain yield under drip irrigation than sprinkler and surface flood irrigation systems. Drought stress and delay sowing date reduced grain yield for all wheat genotypes compared with optimum water irrigation and favorable sowing date. Grain yield over twelve environments ranged from 15.06 for Line 2 to 20.02 (ardab/fad.) for Line 13. Wheat Lines 9, 18 and 21 exhibited the desirable drought and heat sensitivity indices under all irrigation systems (SI < 1). The mean square of joint regression exhibited highly significant differences among genotypes (G), environments (E), the G x E interaction, (E + G × E) and environment (linear). Also, the linear interaction (G x E linear) was highly significant when tested against pooled deviation. Phenotypic stability parameters indicated that bread wheat genotypes Misr 1, Line 13, Line 14 and Line 3 and durum lines 31 (G33), 33 (G35) and 32 (G34) were highly adapted to favorable environments, whereas G36 (Line 34) was adapted to drought stress and delay sowing date environments. Genotypic stability parameters showed that the most desired and stable wheat genotypes were Line 10 and Misr 1. The AMMI analysis of variance showed that environments explained 77.21% of total variation and it was greater than genotypes (5.30%) and genotype × environment (GEI) (12.54%). IPCA 1 score explained 25.08% and IPCA 2 had 17.81% of the total GEI for AMMI model. Whereas, IPCA 1 score explained 36.02% and IPCA 2 had 17.56% of the total GGEI for SREG model. According to the ASV ranking the bread wheat genotypes, Line 10, Giza 168, Line 15, Line 8 and Sakha 93 and durum line 31 (G33) were more stable. GGE biplot exhibited Line 3 as ideal wheat genotype for grain yield. Positive and significant correlation coefficients between , b_i, α_i and P_i were found among each other. The stability parameters i.e., S²_di, λ_i, W²_i, CV (%) and ASV were significantly correlated between each other, indicating that they measured similar aspects of stability.