Application of physiological and biochemical indices for screening and assessment of drought tolerance in durum wheat genotypes

Field experiments were conducted at the Khorasan-e- Razavi Agricultural and Natural Resource Research Center, in Mashhad during the 2007 and 2008 season, to determine drought tolerance in promising durum wheat genotypes. The experiments were laid out using a split plot arrangement, in randomized complete block design with three replications. Four irrigation regimes and five wheat genotypes were assigned to the main-plots and sub-plots respectively. Analysis of the data showed that with advancement of the growth and developmental stages from booting to anthesis and soft dough in the different wheat genotypes planted, the values of relative water content, canopy temperature depression and proline accumulation in leaves, decreased under both optimum and water deficit conditions. In addition, water limitation during grain filling significantly decreased relative water content and canopy temperature depression at the soft dough stage. It caused an increase in the proline content by 22%, 47% and 114% in the vegetative, reproductive and grain filling stages respectively, compared to the control. The findings also showed that the highest values for relative water content, canopy temperature depression and proline accumulation at the different growth and developmental stages of the plants under water deficit conditions, belonged to the G2 durum wheat genotype (RASCON_37/BEJAH_7) compared to the other bread and durum wheat genotypes studied. From the results, it can be concluded that this promising genotype is able to maintain high levels of relative water content under water deficit conditions. This study has also shown that the physiological and biochemical indices used to evaluate plant response to water deficit were effective in assessing promising durum wheat genotypes for drought tolerance.