Variation in seed germination and amylase activity of diverse carrot [daucus carota (L.)] germplasm under simulated drought stress

Authors: NIJABAT, ANEELA - Ghazi University; MANZOOR, SABA - University Of Sargodha; FAIZ, SAMIA - University Of Sargodha; NAVEED, NAIMA HUMA - University Of Sargodha; BOLTON, ADAM - University Of Wisconsin; KHAN, BILAL AHMAD - University Of Sargodha; ALI, AAMIR - University Of Sargodha; Simon, Philipp

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2022
Publication Date: 2/1/2023
Citation: Nijabat, A., Manzoor, S., Faiz, S., Naveed, N., Bolton, A., Khan, B., Ali, A., Simon, P.W. 2023. Variation in seed germination and amylase activity of diverse carrot [daucus carota (L.)] germplasm under simulated drought stress. HortScience. 58(2):205-214. https://doi.org/10.21273/HORTSCI16806-22.
DOI: https://doi.org/10.21273/HORTSCI16806-22

Interpretive Summary: Drought is an environmental challenge that is growing globally for most crops, including carrots. Carrot seed germination is known to be reduced by drought, and for this project, variation in germination rate for a collection of 250 diverse carrot varieties from 41 countries was evaluated to determine if some carrots might be able to begin growing with limited available water. Germination rate was reduced on average by ~30%, and in a few cases up to 100%. But for 9 carrots from Europe and Asia, reduction in carrot seed germination under drought stress was less than 10%, suggesting that it may be possible to reduce the threat of drought losses to carrot by breeding for tolerance. This research is of interest to vegetable growers and seed companies, as well as plant breeders and physiologists.

Technical Abstract: Drought is one of the major environmental challenges which constraints the production of agricultural crops including carrot. Seed germination is the initial but most critical stage of seedling establishment and very sensitive to drought stress, as water scarcity affects the enzymatic solubilizsation of stored metabolites in seeds which provide energy for growth of germinating embryo. Few studies have been published evaluating the effect of drought stress on carrot seed germination of only one cultivar under less stress regimes. Therefore, the present study was designed to define the appropriate osmotic potential for evaluating drought tolerance in carrot, to evaluate the response of diverse carrot germplasm to drought stress during seed germination to identify drought tolerant accessions that may be used by plant breeders, and to evaluate the relation between biochemical enzymes and germination vigor of drought tolerant and sensitive accessions. To identify an appropriate screening osmotic potential, twofour commercial cultivars and two USDA inbreds were evaluated at six osmotic potentials (00, -0.30, -0.51, -0.58, -0.80, and -1.05 MPa). In preliminary studies, -0.58 MPa was identified as the optimal osmotic potential for screening drought tolerance of carrot seed. Cultivated and wild carrot plant introductions (n = 200 and 50 respectively) from the United States Department of Agriculture (USDA) National Plant Germplasm System representing 41 countries were evaluated for drought tolerance under nonstress and simulated drought stress and conditions (00 MPa and -0.58 MPa, respectively) by calculating absolute decrease in percent germination (AD), inhibition index (II), relative drought tolerance (RDT), and drought tolerance index (DTI). All measurements of drought tolerance identified significant differences among accessions; AD ranged from 0.0% to 69.3%, II ranged from 0.0% to 80.2%, RDT ranged from 0.2 to 1.0, and DTI ranged from 0.13 to 1.47. All wild carrot accessions displayed low levels of drought tolerance but PI 652387 and PI 177381 (Turkey), and PI 274297 (Pakistan) were most drought sensitive while cultivated accessions PI 643114 (USA), PI 652208 (China), and PI 502347 (Uzebekistan) were most drought tolerant. Tolerant accessions displayed less decrease in a-amylase activity than sensitive accessions as compared to their respective control under six osmotic potentials (ranging from 0.0 to -1.05 MPa) during 24, 48, and 72 hours of seed germination. This is the first evaluation of drought stress tolerance during seed germination and enzymatic response in diverse carrot germplasm under simulated drought stress.