Transcriptome analysis of the taproot meristem region in contrasting orange carrot breeding lines under varying levels of drought stress

Abstract

Climate change has intensified the impact of abiotic stresses on global crop production, with drought emerging as a significant threat to agricultural productivity. Carrot, a major vegetable crop, is particularly vulnerable to drought, which severely hampers its growth and yield. To address this challenge and ensure food security in the face of current and future climatic shifts, it is important to screen and adapt carrot varieties for improved drought tolerance. Therefore, current study was conducted to observe the response of two different orange carrot lines (B2566B and NB3999) under two drought stress levels (85% and 70%) under semi-controlled greenhouse conditions. Results showed that carrot line B2566B exhibited reduced leaf numbers and a 50% increase in lipid peroxidation under drought stress conditions. Contrarily, carrot line NB3999 showed minimal reductions in root length and diameter. Higher H₂O₂ content was observed in B2566B, while NB3999 had increased total phenolic content, total antioxidant activity, and antioxidant enzymatic activity, indicating its tolerance to drought stress. Physio-biochemical traits in NB3999 confirmed its resilience to drought stress at both 85% and 70% levels. The root meristematic tissue of both lines was used for transcriptomic analysis. RNA-Seq analysis identified 788 genes upregulated in NB3999 under drought conditions compared to B2566B. qRT-PCR validation confirmed significant upregulation of these genes under 70% and 85% drought stress, with two genes, PER (peroxidase N1-like) and CYT (cytochrome P450), showing downregulation. This study provided insights into the transcriptional and biochemical mechanisms underlying the drought tolerance of NB3999, in contrast to the sensitivity observed in B2566B. The findings may support future breeding programs for developing drought-tolerant carrot varieties.