Effects of drought stress and nitrogen nutrition on seed yield and proline content in bread and durum wheat genotypes

This field study was conducted to evaluate the effect of drought stress after anthesis on proline content and seed yield of four wheat genotypes during 2009-2010 in Research Farm of Faculty of Agriculture, University of Tabriz, Iran, as a factorial split plot experiment based on randomized complete block design with three replications. Water stress levels were irrigation in 20,40 and 60% field capacity depletions and used from flag leaf initiation. Nitrogen levels were 20, 40, 60 and 80 kg ha(-1) Studied genotypes were Alvand and Shahriar bread wheat and PGS 01-60-335 and IDW 01-61-130 durum wheat. The results showed that maximum amount of seed yield and proline content was obtained from 80 kg ha(-1) nitrogen fertilizer application treatment. Result of combined analysis showed that the effect of year was significant on seed yield but it had no significant effect on proline content. Under severe water stress (60% field capacity depletion) conditions and 80 kg ha(-1) nitrogen, seed yield of Alvand, Shahryar, Durum PGS 01-60-335 and Durum IDW 01-61-130 showed 72%, 75%, 54% and 44% decrease in the first year and 72%, 71%, 55% and 45% decline during the second year compared to normal conditions (20% field capacity depletion). Meanwhile, proline content of flag leaf in Alvand, Shahriar, Durum PGS 01-60-335 and Durum 01-61-130 were increased by 16.17, 15,76, 19.43 and 20.39 fold, respectively. Data showed that under 80 kg ha(-1) nitrogen and lack of water stress (20% field capacity depletion), the maximum and minimum yield were recorded in Alvand and Durum IDW 01-61-130 during two years. In contrast, under severe water stress (60% field capacity depletion) conditions, maximum and minimum yield were recorded in Durum IDW 01-61-130 and Shahriar. Under severe water stress conditions, the major decrease in seed yield and the minimum increase in proline content were documented in Alvand and Shahriar. However, the lowest decrease in seed yield, and the highlighted increase in proline content were measured in Durum PGS 01-60-335 and IDW 01-61-130 genotypes. In total, water deficit stress had adverse effects on yield of wheat genotypes and nitrogen fertilization had negligible potential to compensate the deteriorative effects of drought condition.