Application of Phenotyping Methods in Detection of Drought and Salinity Stress in Basil (Ocimum basilicum L.)

Boris Lazarević; Zlatko Šatović; Ana Nimac; Monika Vidak; Jerko Gunjača; Olivera Politeo; Klaudija Carović-Stanko

doi:10.3389/fpls.2021.629441

Application of Phenotyping Methods in Detection of Drought and Salinity Stress in Basil (Ocimum basilicum L.)

Front Plant Sci. 2021 Feb 18:12:629441. doi: 10.3389/fpls.2021.629441. eCollection 2021.

Authors

Boris Lazarević^{1

2}, Zlatko Šatović^{2

3}, Ana Nimac², Monika Vidak², Jerko Gunjača^{2

4}, Olivera Politeo⁵, Klaudija Carović-Stanko^{2

3}

Affiliations

¹ Department of Plant Nutrition, Faculty of Agriculture, University of Zagreb, Zagreb, Croatia.
² Centre of Excellence for Biodiversity and Molecular Plant Breeding (CroP-BioDiv), Faculty of Agriculture, University of Zagreb, Zagreb, Croatia.
³ Department of Seed Science and Technology, Faculty of Agriculture, University of Zagreb, Zagreb, Croatia.
⁴ Department of Plant Breeding, Genetics and Biometrics, Faculty of Agriculture, University of Zagreb, Zagreb, Croatia.
⁵ Department of Biochemistry, Faculty of Chemistry and Technology, University of Split, Split, Croatia.

Abstract

Basil is one of the most widespread aromatic and medicinal plants, which is often grown in drought- and salinity-prone regions. Often co-occurrence of drought and salinity stresses in agroecosystems and similarities of symptoms which they cause on plants complicates the differentiation among them. Development of automated phenotyping techniques with integrative and simultaneous quantification of multiple morphological and physiological traits enables early detection and quantification of different stresses on a whole plant basis. In this study, we have used different phenotyping techniques including chlorophyll fluorescence imaging, multispectral imaging, and 3D multispectral scanning, aiming to quantify changes in basil phenotypic traits under early and prolonged drought and salinity stress and to determine traits which could differentiate among drought and salinity stressed basil plants. Ocimum basilicum "Genovese" was grown in a growth chamber under well-watered control [45-50% volumetric water content (VWC)], moderate salinity stress (100 mM NaCl), severe salinity stress (200 mM NaCl), moderate drought stress (25-30% VWC), and severe drought stress (15-20% VWC). Phenotypic traits were measured for 3 weeks in 7-day intervals. Automated phenotyping techniques were able to detect basil responses to early and prolonged salinity and drought stress. In addition, several phenotypic traits were able to differentiate among salinity and drought. At early stages, low anthocyanin index (ARI), chlorophyll index (CHI), and hue (HUE₂ _D ), and higher reflectance in red (R _Red ), reflectance in green (R _Green ), and leaf inclination (LINC) indicated drought stress. At later stress stages, maximum fluorescence (F _m ), HUE₂ _D , normalized difference vegetation index (NDVI), and LINC contribute the most to the differentiation among drought and non-stressed as well as among drought and salinity stressed plants. ARI and electron transport rate (ETR) were best for differentiation of salinity stressed plants from non-stressed plants both at early and prolonged stress.

Keywords: 3D scanning; chlorophyll fluorescence imaging; drought stress; high-throughput phenotyping; salinity stress.