Abstract
Tomato (Solanum lycopersicum L.) is an important vegetable cultivated around the world. Under field conditions, tomato can be negatively affected by water scarcity in arid and semiarid regions. The application of native plant growth-promoting rhizobacteria (PGPR) isolated from arid environments has been proposed as an inoculant to mitigate abiotic stresses in plants. In this study, we evaluated rhizobacteria from Cistanthe longiscapa (syn Calandrinia litoralis and Calandrinia longiscapa), a representative native plant of flowering desert (FD) events (Atacama Desert, Chile), to determine their ability to reduce water scarcity stress on tomato seedlings. The isolated bacterial strains were characterized with respect to their PGPR traits, including P solubilization, 1-aminocyclopropane-1-carboxylate deaminase activity, and tryptophan-induced auxin and exopolysaccharide production. Three PGPR consortia were formulated with isolated Bacillus strains and then applied to tomato seeds, and then, the seedlings were exposed to different levels of water limitations. In general, tomato seeds and seedlings inoculated with the PGPR consortia presented significantly (P ≤ 0.05) greater plant growth (48 to 60 cm of height and 171 to 214 g of weight) and recovery rates (88 to 100%) compared with those without inoculation (37 to 51 cm of height; 146 to 197 g of fresh weight; 54 to 92% of recovery) after exposure to a lack of irrigation over different time intervals (24, 72 and 120 h) before transplantation. Our results revealed the effectiveness of the formulated PGPR consortia from FD to improve the performance of inoculated seeds and seedlings subjected to water scarcity; thus, the use of these consortia can represent an alternative approach for farmers facing drought events and water scarcity associated with climate change in semiarid and arid regions worldwide.
Highlights
Tomato (Solanum lycopersicum L.) is an important vegetable cultivated around the world
Initial mixture analyses indicated that the assembled consortia maintained their plant growth promoting (PGP) traits but that some had higher PGP activities, with values of tryptophan-induced auxin production of indole acetic acid mL−1 increasing from 118.2 to 122.6 μg (3.7% increase), aminocyclopropane-1-carboxylate deaminase (ACCD) activity increasing from 27.1 to 68.7 μmol of α-ketobutyrate h −1 g protein−1 (253.5% increase), and EPS production increasing from 1085.3 to 3077.5 μg sucrose m L−1 supernatant (283.6% increase) (Table 2)
The formulation of plant growth-promoting rhizobacteria (PGPR) consortia that provide a higher tolerance of vegetables to water scarcity may be pivotal as a complementary technology to face the current scenario of climate change in the Mediterranean and semiarid and arid agricultural zones worldwide[63,67,68], including northern Chile, where the availability and quality of water are critical to support vegetable production for human consumption. This current study revealed the occurrence of culturable rhizobacteria harboring PGP traits in the rhizosphere of C. longiscapa growing during an flowering desert (FD) event
Summary
Tomato (Solanum lycopersicum L.) is an important vegetable cultivated around the world. In Chile, desertification processes represent a major risk and directly affect the vegetable production of the country because of the persistent drought conditions that have affected the country for the last 10 to 15 y ears[3] To resolve this limitation, studies have proposed the search, selection and use of cultivars with a higher tolerance to stress because of water scarcity; this alternative is time consuming and costly to implement in many extensive agricultural areas in arid and semiarid regions affected by climate change[4,5]. Native plants and their microbiota have coevolved under arid conditions; recent studies have proposed the use of PGPR from arid environments as inoculants to mitigate the damage of water limitation (drought) stress in plants In this context, inoculation of wheat with consortia of PGPR isolated from the Atacama Desert (AD) improved plant growth under water shortage conditions[13]. Tomato was selected as a model plant because it is one of the main freshly consumed vegetables in Chile and its final production is very sensitive to environmental stresses at initial phenological s tages[17]
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