Distinct morpho-physiological and biochemical features of arid and hyper-arid ecotypes of Ziziphus nummularia under drought suggest its higher tolerance compared with semi-arid ecotype

Abstract

Tree species in the arid and semi-arid regions use various strategies to combat drought stress. Ziziphus nummularia, native to the Thar Desert in India, is highly drought-tolerant. To identify the most drought-tolerant ecotype of Z. nummularia, one ecotype each from semi-arid (Godhra, annual rainfall > 750 mm), arid (Bikaner, 250–350 mm) and hyper-arid (Jaisalmer, < 150 mm) regions was selected along with two other Ziziphus species; Z. mauritiana and Z. rotundifolia, and screened for parameters contributing to drought tolerance. Among these, Z. nummularia (Jaisalmer) (CIAHZN-J) was the most drought-tolerant. The tolerance nature of CIAHZN-J was associated with increased membrane stability, root length and number, length of hairs and thorns, root dry/fresh weight ratio, seed germination (at −0.5 MPa), proline content (31 fold), catalase and sugar content (2 to 3 fold). Apart from these characteristics, it also exhibited the longest duration to reach highest cumulative drought stress rating, maintained higher relative water content for a longer period of time with reduced leaf size, leaf rolling and falling of older leaves, and displayed sustained shoot growth during drought stress. To determine drought tolerance in Ziziphus, we developed a morphological symptom-based screening technique in this study. Additionally, transcriptome profiling of CIAHZN-J in response to drought revealed the up-regulation of genes involved in sugar metabolism and transport, ABA biosynthesis, osmo-regulation, ROS homeostasis and maintaining water potential. Expression profiles and semi-quantitative reverse transcription PCR results further correlated with the physiological and biochemical mechanisms. In conclusion, CIAHZN-J is an excellent genetic stock for the identification of drought-responsive genes and can also be deployed in crop improvement programmes for drought tolerance.

Comparative Study of Phytosociological Status of Herbs and Shrubs in Nanta Forest Region, Rajasthan, India

“…The species Ziziphus nummularia (Burm.f.) Wight & Arn is highly draught tolerant and can survive in harsh conditions [29]. The species Prosopis juliflora (Swartz) DC.…”

Ziziphus nummularia: A Comprehensive Review of Its Phytochemical Constituents and Pharmacological Properties

“…Sivalingam et al [53] screened the parameters contributing to drought tolerance by comparing three Ziziphus nummularia ecotypes from semi-arid, arid and hyper-arid regions. Results showed that the latter was the most drought-tolerant ecotype and was associated with an increase in root length and number, an increase in leaf hair growth, and in elongation of thorns.…”

“…In order to maintain a high relative water content for longer periods of time, membrane permeability was increased, and proline, catalase and sugar content was higher. Transcriptome profiling showed that genes associated with drought response mechanisms were constitutively expressed at higher levels [53].…”