Wheat grain tyrosinase activity as an index of drought resistance

Two bread wheat cultivars (Triticum astivum L. cvs. Abu-Ghraib,3 and Mexipak) and two of Macroni wheat (Triticum durum Desf. Acsad-65 and Om-Rabi-5) were subjected to various levels of water stress (−0.6, −0.8, −1 Mpa in addition to −0.03 Mpa, field capacity). Phenol reaction test was substituted with tyrosine also carried out, the spectrophotometers for steeped water of soaked seeds in 0.5% tyrosine aqueous solution was measured to detect tyrosinase enzyme activity. Results revealed that the two bread wheat were more drought resistance than durum wheat cultivars as they were less affected by water stress and particularly Abu-Ghraib,3 cultivar which was superior over all involved cultivars it displayed the lowest reductions in growth characters in comparison to that grown under field capacity. Besides Abu-Ghraib,3 was the only cultivar manifested the dark black coloration with tyrosine test, and also gave high absorbance of spectrophotometer at 280 nm which indicates highest tyrosinase activity. These results confirm that phenol can be successfully substituted with tyrosine for wheat varietals identification as the former ones is caustic, hateful and harmful smell. From the obtained results we may inferred that tyrosinase enzyme activity as spectrophotometer absorbance can consider as index for wheat cultivars drought resistance.