Performance of Some Bread Wheat Genotypes under Different Irrigation Regimes and Nitrogen Fertilizer

Twenty four wheat genotypes (Triticum aestivum L.), differ in yield performance were grown in a randomized complete block experimental design with three replications during two seasons 2004/2005 – 2005/2006 at Sohag University experimental Farm. The genotypes were evaluated under three water regimes (control treatment (I₁), stress treatment (I₂) and high stress treatment (I₃)) and two nitrogen fertilizer levels (70 Kg N and 100 Kg N/fed.). The analysis of variance for all parameters as affected by water regimes (I), two different N fertilizer levels (N) and the genotypes (G) and their interactions were carried and were fund to be significant. The treatments of nitrogen fertilizer (70 Kg N/fed.) and control irrigation treatment (I₁) over two years produced the highest grain yield from the five genotypes No. Giza 168, 9, 12, 18 and 21. While the five genotypes namely No. 5, 8, 18, 21 and 22 gave the highest yield when fertilizer with 70 Kg N/fed. with stress irrigation treatment (I₂), on other hand the five genotypes No. 14, 16, 18, 19 and 22 gave the highest yield when treated with 70 Kg N/fed. with high stress irrigation treatment (I₃). The result showed that application of 100 Kg N/fed. with regular (I₁) over two years the five genotypes No. Giza 168, 9, 12, 18 and 21 gave the highest yield, while the highest five genotypes were No. 5, 8, 16, 18 and 21 under 100 Kg N/fed . with stress irrigation treatment (I₂), on other hand the five genotypes No. 14, 16, 18, 19 and 22 gave the highest yield under 100 Kg N/fed and the highest stress irrigation treatment (I₃). The results showed that mean productivity (MP), geometric mean productivity (GMP) and stress tolerance index (STI) were more effective in identifying the high yielding genotypes under control treatment (I₁) and stress treatment (I₂) (group A genotypes). Under high stress treatment, none of the indices used were able to identify group A cultivars, although stress susceptibility index (SSI) was found to be more useful in discriminating the drought tolerance genotypes. It is concluded that the effectiveness of selection indices in differentiating drought tolerance genotypes varies with the high stress treatment. The correlations between control irrigation, drought stress, high drought stress and yield during two seasons were positive and highly significant (0.84**, 0.86** and 0.58**).