Abscisic acid-mediated modulation of morpho-physiological traits and transcript accumulation improves drought resilience in Crocus sativus L.

Abstract

Drought is a major abiotic factor leading to decreased productivity. The current study investigates the effects of prolonged drought stress and subsequent recovery in Crocus sativus L. through the exogenous application of abscisic acid (ABA) under field conditions in the Dhauladhar range of the Himalayan region. To evaluate the influence of drought stress, saffron corms (both large and medium) were subjected to three treatments: irrigation, water deficit (withheld irrigation), and ABA application (via foliar spray). The results indicated that morphological and physiological traits, including fresh weight and dry weight (leaf, root, mother corm and daughter corm), sprouting percentage, total biomass, flower number, stomatal aperture, relative water content, photosynthetic activity and Fv/Fm were negatively affected by drought stress. Further, histological analysis revealed a reduction in starch granule accumulation, while root metaxylem cells were found to be enlarged under water deficit conditions. Additionally, RT-PCR analysis indicated higher transcript abundance of DREB1, DREB2 and SnRK2 under drought conditions compared to the control, while the expression levels of MYB37, WRKY1, DHN1, DHN1 and AREB1 remained unchanged under similar conditions. Nevertheless, exogenous abscisic acid improved the drought tolerance of C. sativus. A decrease in lipid peroxidation and an increase in proline, chlorophyll content, and antioxidant activity were observed when ABA was applied under drought conditions. Overall, our study demonstrates ABA-mediated regulation of several key transcription factors under drought stress. These findings provide new insights into the mechanisms of drought tolerance in saffron, which will facilitate future breeding programmes for this highly valuable crop.