Phenotypic responses to drought stress in wheat on genotype, plant and single seed level

Plant phenotyping reveals relationships between measured plant parameters and environmental conditions, thus enabling the study of plant genotype-environment interactions. In our approach we aim to better understand how drought stress during the vegetative phase affects growth and physiological plant responses and thus feeds back on seed traits at harvest. In a greenhouse experiment, nine wheat cultivars selected from the ‘10+ Wheat Genomes Project’ were scanned twice a week for approximately 5 months using the 3D phenotyping system 'Plant Eye'. After harvest, biometric seed traits, such as mass and volume of individual seeds, were phenotyped using the ‘phenoSeeder’. Drought stress resulted in a mean plant biomass reduction by 31%, but also induced genotype-specific responses. The CDC Landmark, CDC Stanley, Norin and Weebil cultivars were generally most sensitive to drought stress, while cv Arina, Cadenza, Chinese Spring, Jagger and Mace showed higher tolerance. Seed characteristics showed high variability among cultivars and plant individuals. Mean values of seed mass ranged from 43 mg (Chinese Spring) to 70 mg (Weebil). Generally, intra-genotype distributions of seed volume and mass were rather wide, with at least a factor two between the values for the smallest and biggest seeds. The drought treatment reduced seed mass and volume only in the cv Chinese Spring and Weebil. Moreover, we did not find any effect of drought stress on seed density. Thus, the drought stress effect on seed traits was different from the response seen in plant biomass and yield. Overall, the applied phenotyping tools allowed for a non-invasive quantification of plant and seed responses on genotype, individual plant and single seed level. We believe that the combination of the different phenotyping approaches, seed classification and seed selection will help to more efficiently identify the genetic basis of complex traits such as drought resistance