Monitoring Solanum lycopersicum var. Elpida salinity stress using multispectral imaging

Under salinity stress, plant physiology and yield characteristics deteriorate, showing, among others, symptoms similar to those of water stress. Tomato (Solanum lycopersicum) is moderately sensitive to salinity stress and suffers yield losses of over 15% at irrigation water electrical conductivity (EC_w) of  3 dSm^-1 (Malash et al., 2008) and over 25% at EC_w of 3.5 dSm^-1 (Daliakopoulos et al., 2019). As salinity can often buildup in soils and substrates, it can have a creeping effect not readily measurable in irrigation water EC_w, therefore it is essential that plant physiology symptoms are spotted early to take corrective action. Here we investigate the potential of multispectral imaging, to detect early symptoms of salinity stress on S.lycopersicum plants (var. Elpida) due to NaCl accumulation in the nutrient solution of a soilless cultivation system. In this context, we established a control (0.5 mM) and five salinity treatments of 5.0, 10.0, 15.0, 20.0 mM NaCl, with three tomato plants (replications) per treatment, resulting in a total number of 18 S.lycopersicum plants. During the experiment, multispectral images (bands 460, 540, 630, 850, and 980 nm) were obtained at three stages of plant development (30, 60, and 90 days after transplant) using a MUSES9-MS sensor. For each multispectral image, four spectral indices (NDVI, OSAVI, LWSI and GOSAVI) were calculated. Although, the statistical analysis of the results reveal low sensitivity to the increasing salinity at early sampling stage (60 DAT), during the third sampling stage (120 DAT) all spectral indicators demonstrate significant sensitivity for treatments over 10.0 mM NaCl.

References

Daliakopoulos, I.N., Apostolakis, A., Wagner, K., Deligianni, A., Koutskoudis, D., Stamatakis, A., Tsanis, I.K., 2019. Effectiveness of Trichoderma harzianum in soil and yield conservation of tomato crops under saline irrigation. Catena 175. https://doi.org/10.1016/j.catena.2018.12.009

Malash, N.M., Ali, F.A., Fatahalla, M.A., A. khatab, E., Hatem, M.K., Tawfic, S., 2008. Response of tomato to irrigation with saline water applied by different irrigation methods and water management stratigies. Int. J. Plant Prod. 2, 101–116.

Acknowledgements
This research has been co-financed by the European Union and Greek national funds through the Operational Program Competitiveness, Entrepreneurship, and Innovation, under the call RESEARCH-CREATE-INNOVATE (project codes: T1EDK-04171)