Digital phenotypes during recurrent drought stress: screening of a tomato collection

Due to its subtropical origin, tomato requires large amounts of water during summer, which is the cropping season in the South of Italy and large areas of the Mediterranean Basin. Due to climate change, dry spells are becoming increasingly frequent and intense, requiring alternative crop management strategies, including adoption of genotypes less vulnerable to recurrent drought. High throughput phenotyping approaches enable the dissection of the complexity underlying the response to water deficit through large scale, multi-traits screenings, and are amenable of integration with molecular and biochemical data of different nature. Here, we performed a recurrent stress trial on 15 tomato genotypes usingthe HTP plant phenotyping platform at ALSIA. Plants were grown in 3.2L pots containing 1.8 kg of a sand/peat mixture. Drought stress was appliedthrough a 70% reduction in irrigation water in two stress cycles followedby recovery stages. During the 6 weeks trial, RGB and NIR images wereacquired in 11 dates, corresponding to distinct experimental points, toobtain digital phenotypes of the control and drought stressed plants.Physiological and morphometric parameters estimated will includeevapotranspiration, chlorophyll content, water use efficiency, solidity andheight. Estimation of projected canopy area after the second recovery showed a growth penalty caused by drought stress in all genotypes, of different magnitude. Red Setter, Eventus and Cerise were least impacted, with a canopy area reduction of around 5% in drought condition compared to control, whereas 770P, Seccagno and San Marzano Nano were more vulnerable to drought stress, with a canopy area reduction of about 17%. These results well correlated with shoot fresh weight measurements. Proline content evaluation after the first drought cycle showed 5-6 times higher amounts in stressed samples than that of the controls in all tested genotypes, while after the second stress cycle the proline levels were comparable in the two conditions. Data analyses are ongoing and are being used to estimate progression of morphophysiological parameters over time, whereas changes in gene expression of stress related genes will contribute to the identification of differential responses among genotypes.