Alleviation of NaCl stress in tomato varieties by promoting morpho-physiological attributes and biochemical characters

Salinity is a significant abiotic stress, affecting plant growth and productivity during all plant developmental stages. Soil salinization due to climate change is increasing crop loss every year. Salinity is considered the most important abiotic stress limiting crop production and plants are known to be able to continue to survive under this stress by involving many mechanisms. Vegetable crops face huge yield losses due to abiotic stress. Salt stress creates physiological drought in plants affecting morphology and alters physiological functions that harm plants through various processes. Tomato is an essential annual crop providing human food worldwide. It is estimated that by the year 2050 > 50% of the arable land will become saline and, in this respect, in recent years, researchers have focused their attention on studying how tomato plants behave under various saline conditions. This study was conducted to observe the effects of NaCl salinity on four tomato (Lycopersicum esculentum L.) varieties in a pot experiment. Morphological and physio-biochemical properties of four tomato varieties (Rio Grande, Nadir, Bonita, and 19299) were exposed to NaCl-salinity (0, 100, 200, and 300 mM) through irrigation. All the varieties have differential responses to different levels of salt. Salinity stress reduced growth parameters in all varieties as compared to control plants. Plant Variety 4 (19299) showed significantly increased growth (root length, shoot length, number of roots, number of leaves, leaf area, plant fresh and dry weight) and physiological attributes (photosynthetic pigments, total soluble sugars, and total proteins) as compared to other varieties. Variety 4 (19299) has better protection against salt stress by increasing pigment content and enzymatic activity under salt stress. Antioxidants (peroxidase, catalase, and superoxide dismutase) were increased to maximum in variety 3 (Bonita) which is the most susceptible variety among all other varieties. Malondialdehyde (MDA) content, lycopene, anthocyanin, and H2O2 also increased in Variety 3 as compared to other varieties and control plants. Bonita variety showed maximum reduction in root length, shoot length, number of roots, fresh and dry matter content as well as in leaf area while comparing with other three varieties. The study revealed that the 19299 variety is salt tolerant, Rio Grande and Nadir are intermediates while the Bonita variety is susceptible to salt stress.