RESPONSE OF TUNISIAN DURUM (Triticum turgidum ssp durum) AND BREAD (Triticum aestivum L.) WHEATS TO WATER STRESS

Wheat is a staple crop in Tunisia, but little is known about the response of Tunisian durum wheat (Triticum turgidum ssp. durum) and bread wheat (Triticum aestivum L.) to water stress. In semi-arid regions, where cereals are concentrated, grain yield is subject to water deficit especially due to variability in rainfall. Therefore, the objective of this study was to evaluate the response to water stress of three durum wheat (Maali, Nasr and Salim) and two bread wheat (Tahent and Utique) varieties. The experimental design was a complete randomized block, water treatments were rainfed conditions (TO) and irrigation applied at the tillering and flowering stages (T1, control) with three replications per treatment, and data was analyzed by ANOVA and Tukey test to compare treatments means (p <= 0.05). Variables analyzed were grain yield and yield-related components: plants per square meter (NP), tillers per square meter (NT), ears per square meter (NE), seed per ear (NSE) and 1000-kernel weight (TKW). NP, NE, NSE and TKW were significantly affected by water stress, but there was no change on NT. Seed yield was weakly correlated with NE (r=0.376) but significantly correlated with NSE (r=0.604) and NP (r=0.639). Supplemental irrigation increased grain yield by 74.4 %, 42.3 %, 36.1 %, 33.7 % and 24.5 % for Utique, Tahent, Nasr, Maali and Salim, respectively, compared to control. Four drought tolerance indices, stress tolerance index (STI), stress tolerance (TOL), stress susceptibility index (SSI), and mean productivity (MP), were assessed and were adjusted based on grain yield under drought (Y-e) and normal (Y-p) conditions. A positive and significant correlation between Y-s, and Y-p with SSI and PM, respectively, indicate that they are the most suitable variables to select wheat genotypes in drought stress. These indices were able to screen a drought-tolerant genotype (Nasr), which showed the highest STI (1.10). In contrast, Salim showed the lowest STI (0.47) and was considered to be a drought-susceptible genotype.