Drought Tolerant Trait Identification In Synthetic Hexaploid Wheat.

Improved drought tolerance is a major objective of many plant breeding programs. This research presents the preliminary discovery of traits contributing to drought tolerance found in synthetic hexaploid wheat and their exploitation in bread wheat cultivar development. Experiments were developed for the measurement of physiological traits under greenhouse conditions in 4L pots. Drought stress was introduced to six synthetic lines and two adapted cultivars, Goodstreak and Hatcher. Treatments consisted of well-watered (~85% gravimetric soil water content) and drought stressed conditions (2-3% reduction in gravimetric soil water content per day). In two separate experiments the drought treatment spanned 21 days during vegetative growth and during anthesis, respectively. A replicated split block design was used in each experiment. Repeated measures ANOVA found stomatal conductance, transpiration, internal CO2 concentration and photosynthesis were not different among the varieties (P < 0.05). However, in the vegetative stage experiment, traits such as root and shoot biomass, stomatal density and water use efficiency differed among entries (P < 0.05). Mean root biomass of the synthetic lines reached 111 and 112% of the cultivars in wet and dry conditions, respectively. Root biomass of the synthetic line coded 194 was greater than all other entries while its shoot biomass was greater than both cultivars (P < 0.05), under well-watered conditions. Stomate density showed a mean reduction of 10% in the synthetic lines compared to the cultivars. Also, water use efficiency of the dry treatment, as calculated by the ratio of biomass to water use, showed the synthetic line 194 to be statistically equal to Goodstreak, which out-performed all other lines. Back-cross derived families of synthetic 194 had a superior yield advantage in preliminary field trials. Synthetic derived traits must be further tested in order to assess their potential use as selection criteria in breeding programs.