Cell membrane stability and relative cell injury in response to heat stress during early and late seedling stages of diverse carrot (Daucus carota L.) germplasm

Authors: NIJABAT, ANEELA - University Of Sargodha; BOLTON, ADAM - University Of Wisconsin; MAHMOOD-UR-REHMAN, MUHAMMAD - Ayub Agricultural Research Institute; IJAZ SHAH, ADEL - University Of Sargodha; HUSSAIN, RAMEEZ - University Of Sargodha; NAVEED, NALMA HUMA - University Of Sargodha; ALI, AAMIR - University Of Sargodha; Simon, Philipp

Submitted to: Hortscience Proceedings
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2020
Publication Date: 8/6/2020
Citation: Nijabat, A., Bolton, A., Mahmood-Ur-Rehman, M., Ijaz Shah, A., Hussain, R., Naveed, N., Ali, A., Simon, P.W. 2020. Cell membrane stability and relative cell injury in response to heat stress during early and late seedling stages of diverse carrot (Daucus carota L.) germplasm. Hortscience Proceedings. 55(9):1446-1452. https://doi.org/10.21273/HORTSCI15058-20.
DOI: https://doi.org/10.21273/HORTSCI15058-20

Interpretive Summary: When plants are exposed to high environmental temperatures growth is slowed down, crop productivity and quality is diminished, and when temperatures are high enough, plants will die. While we see these deleterious effects at the whole plant level, they begin at the cellular level with damage to cell membranes which leads to leakage of cellular contents and cell death. Previous studies that quantitative measurements of cell membrane damage are good predictors of the magnitude of reductions in plant growth and crop productivity. All crop plant come from diverse genetic backgrounds and this diversity is the basis for variety-to-variety variation for a given crop. Carrot is a genetically diverse crop and this study evaluated 215 diverse varieties of carrot for variation in cell membrane damage when they were grown for 60 days at 24°C (75°F), but exposing them to high temperatures (35°C or 97°F) at either early seedling stage (days 15-30 after germination) or late seedling stage (31-60 days after germination). A wide range in varying sensitivity to heat was observed among the diverse carrots grown, with some carrots exhibiting minimal membrane damage when exposed to high temperatures at the early seedling stage, or late seedling stage of growth. Carrots with heat tolerance at early seedling stage were not necessarily tolerant at late seedling stage, and vice versa, suggesting that different genes control heat tolerance at different stages of carrot growth. These results are of interest to vegetable growers, seed companies, and researchers studying plant climatic stress tolerance.

Technical Abstract: Heat waves occur with more regularity and they adversely affect the yield of cool season crops including carrot (Daucus carota L.). Heat stress influences various biochemical and physiological processes including cell membrane permeability. Ion leakage and increase in cell permeability are indicators of cell membrane stability and have been used to evaluate the stress tolerance response in numerous crops and inform plant breeders for improving heat tolerance. No study has been published about the effects of heat stress on cell membrane stability and relative cell injury of carrot. Therefore, the present study was designed to estimate these stress indicators in response to heat stress at the early and late seedling developmental stages of 215 diverse accessions of wild and cultivated carrot germplasm. To identify the relationship between early and late stages of seedling tolerance across carrot genotypes and to identify heat tolerant genotypes for further genetic analysis. Significant genetic variation among these stress indicators was identified with cell membrane stability and relative cell injury ranging from 6.3% to 97.3% and 2.8% to 76.6% at the early seedling stage respectively whereas, cell membrane stability and relative cell injury ranged from 2.0% to 94.0% and 2.5% to 78.5% respectively at the late seedling stage under heat stress. Broad-sense heritability ranged from 0.64 to 0.91 for traits of interest under study, which indicates a relatively strong contribution of genetic factors in phenotypic variation among accessions. Heat tolerance varied widely among both wild and cultivated accessions, but the incidence of tolerance was higher in cultivated carrots than in wild carrots. The cultivated carrot accessions PI 326009 (Uzbekistan), PI 451754 (Netherlands), L2450 (USA) and PI 502654 (Pakistan) were identified as the most heat tolerant accessions with highest cell membrane stability. This is the first evaluation of cell membrane stability and relative cell injury in response to heat stress during carrot development.