Contents lists available at ScienceDirect Industrial Crops & Products journal homepage: www.elsevier.com/locate/indcrop Foliar application of KNO 3 modulates the biomass yield, nutrient uptake and accumulation of secondary metabolites of Stevia rebaudiana under saline conditions Mitali Mahajan a,b , Surbhi Sharma a , Pawan Kumar c , Probir Kumar Pal a,b, * a Division of Agrotechnology of Medicinal, Aromatic and Commercially Important Plants, Council of Scientific and Industrial Research-Institute of Himalayan Bioresource Technology (CSIR-IHBT), Post Box No. 6, Palampur 176 061, HP, India b Academy of Scientific and Innovative Research (AcSIR), CSIR-IHBT, Post Box No. 6, Palampur 176 061, HP, India c Division of Natural Product Chemistry and Process Development, Council of Scientific and Industrial Research-Institute of Himalayan Bioresource Technology (CSIR- IHBT), Post Box No. 6, Palampur 176 061, HP, India ARTICLE INFO Keywords: Industrial crop KNO 3 NaCl stress Ion homeostasis Steviol glycosides Total phenols ABSTRACT Stevia rebaudiana Bertoni is quickly becoming an important industrial crop throughout the world. However, the growth, biomass yield and secondary metabolites of stevia are negatively affected when the growing environ- ment is adverse including salt affected soil. Though relatively little is understood of adaptation, physiological and metabolic changes of stevia under exposure to a salinity environment, it is hypothesized that foliar appli- cation of potassium (K + ) could improved the salinity tolerance through ion homeostasis. Thus, an experiment was conducted in two years constitutively with twenty treatment combinations comprising four salinity levels (irrigation with normal water as control and three levels of NaCl at 40, 80 and 120 mM) and exogenous ap- plication of five different concentrations of KNO 3 (water spray as control, KNO 3 at 2.5, 5.0, 7.5, and 10.0 g L −1 ) to understand the sole and interaction effects of both the factors on stevia. The growth parameters and dry leaf yield were not negatively affected with salinity level up to 40 mM, irrespective of KNO 3 levels. However, the detrimental effects were observed at higher salinity (80 and 120 mM). The uptakes of K + , Ca 2+ , and N were significantly (P ≤0.05) reduced at higher salinity whereas accumulations of Na + and Cl − ions in plant tissues were substantially increased. Application of KNO 3 at5.0gL −1 registered significantly (P ≤ 0.05) higher dry leaf yield compared with water spray as control. The biochemical parameters such as total chlorophyll, proline and total phenols, were also significantly (P ≤ 0.05) influenced by the sole effects of salinity and KNO 3 . The negative effects of high salinity on leaf yield were reduced with foliar application of KNO 3 by up to 26 %. Thus, it can be concluded that stevia can be grown in moderate saline (NaCl at 80 mM) conditions with exogenous foliar ap- plication of KNO 3 . 1. Introduction The burgeoning rate of diabetic and obesity patients is a serious concern in the worldwide. Globally, 346 million people are in the grip of diabetes whereas in India 69.2 million people are diabetic (WHO, 2015). Cane sugar (from Saccharum officinarum L.) is not recommended to the diabetic and obesity patients for consumption. In these circum- stances, stevia has emerged to be a natural sweet gift for millions of diabetics as a sweet quotient in their daily life. The stevia leaves contain sweet-tasting and low-calorie diterpenoid steviol glycosides (SGs), which are nearly 300 times sweeter than sucrose (Kinghorn, 2002). Among the identified SGs present in the stevia leaf so far, stevioside (ST) and rebaudioside-A (Reb-A) are the most abundant compounds (Kinghorn and Soejarto, 1991). Steviol glycosides from the stevia leaf are quickly becoming an important ingredient for beverage and food industries as a sweetener and flavour enhancer. Additionally, stevia plants have several biochemical constituents, which show importance in the pharmaceutical industry. Now stevia is successfully grown as an industrial crop in wide agro-ecological conditions of China, Japan, Brazil, Mexico, Russia, Indonesia, Korea, USA, India and Canada (Brandle et al., 1998; Pal et al., 2015a, 2017). Crop-ecology and agro- nomic factors essentially influence the growth and accumulation of https://doi.org/10.1016/j.indcrop.2020.112102 Received 24 August 2019; Received in revised form 5 January 2020; Accepted 6 January 2020 ⁎ Corresponding author at: Division of Agrotechnology of Medicinal, Aromatic and Commercially Important Plants, Council of Scientific and Industrial Research- Institute of Himalayan Bioresource Technology (CSIR-IHBT), Post Box No. 6, Palampur 176 061, HP, India. E-mail address: palpk@ihbt.res.in (P.K. Pal). Industrial Crops & Products 145 (2020) 112102 0926-6690/ © 2020 Elsevier B.V. All rights reserved. T